diff --git a/doc/mkdocs/docs/api/basic_json/at.md b/doc/mkdocs/docs/api/basic_json/at.md
index fc518f46e4..e4123cdad1 100644
--- a/doc/mkdocs/docs/api/basic_json/at.md
+++ b/doc/mkdocs/docs/api/basic_json/at.md
@@ -6,8 +6,10 @@ reference at(size_type idx);
 const_reference at(size_type idx) const;
 
 // (2)
-reference at(const typename object_t::key_type& key);
-const_reference at(const typename object_t::key_type& key) const;
+template<typename KeyType>
+reference at(const KeyType& key);
+template<typename KeyType>
+const_reference at(const KeyType& key) const;
 
 // (3)
 reference at(const json_pointer& ptr);
@@ -18,6 +20,13 @@ const_reference at(const json_pointer& ptr) const;
 2. Returns a reference to the object element at with specified key `key`, with bounds checking.
 3. Returns a reference to the element at with specified JSON pointer `ptr`, with bounds checking.
 
+## Template parameters
+
+`KeyType`
+:   A type for an object key other than [`json_pointer`](../json_pointer/index.md) that is comparable with [`string_t`](string_t.md)
+    using [`object_comparator_t`](object_comparator_t.md).
+    This can also be a string literal or a string view (C++17).
+
 ## Parameters
 
 `idx` (in)
@@ -172,5 +181,5 @@ Strong exception safety: if an exception occurs, the original value stays intact
 ## Version history
 
 1. Added in version 1.0.0.
-2. Added in version 1.0.0.
+2. Added in version 1.0.0. Added `KeyType` template in version 3.11.0.
 3. Added in version 2.0.0.
diff --git a/doc/mkdocs/docs/api/basic_json/contains.md b/doc/mkdocs/docs/api/basic_json/contains.md
index 8463f4ea98..cb83de3913 100644
--- a/doc/mkdocs/docs/api/basic_json/contains.md
+++ b/doc/mkdocs/docs/api/basic_json/contains.md
@@ -2,8 +2,8 @@
 
 ```cpp
 // (1)
-template<typename KeyT>
-bool contains(KeyT && key) const;
+template<typename KeyType>
+bool contains(const KeyType& key) const;
 
 // (2)
 bool contains(const json_pointer& ptr) const;
@@ -15,8 +15,10 @@ bool contains(const json_pointer& ptr) const;
 
 ## Template parameters
 
-`KeyT`
-:   A type for an object key other than `basic_json::json_pointer`.
+`KeyType`
+:   A type for an object key other than [`json_pointer`](../json_pointer/index.md) that is comparable with [`string_t`](string_t.md)
+    using [`object_comparator_t`](object_comparator_t.md).
+    This can also be a string literal or a string view (C++17).
 
 ## Parameters
 
@@ -90,5 +92,5 @@ Logarithmic in the size of the JSON object.
 
 ## Version history
 
-1. Added in version 3.6.0.
+1. Added in version 3.6.0. Extended template `KeyType` to support any comparable type in version 3.11.0.
 2. Added in version 3.7.0.
diff --git a/doc/mkdocs/docs/api/basic_json/count.md b/doc/mkdocs/docs/api/basic_json/count.md
index fcfef86737..71439ea542 100644
--- a/doc/mkdocs/docs/api/basic_json/count.md
+++ b/doc/mkdocs/docs/api/basic_json/count.md
@@ -1,8 +1,8 @@
 # <small>nlohmann::basic_json::</small>count
 
 ```cpp
-template<typename KeyT>
-size_type count(KeyT&& key) const;
+template<typename KeyType>
+size_type count(const KeyType& key) const;
 ```
 
 Returns the number of elements with key `key`. If `ObjectType` is the default `std::map` type, the return value will
@@ -10,8 +10,10 @@ always be `0` (`key` was not found) or `1` (`key` was found).
 
 ## Template parameters
 
-`KeyT`
-:   A type for an object key.
+`KeyType`
+:   A type for an object key other than [`json_pointer`](../json_pointer/index.md) that is comparable with [`string_t`](string_t.md)
+    using [`object_comparator_t`](object_comparator_t.md).
+    This can also be a string literal or a string view (C++17).
 
 ## Parameters
 
@@ -53,3 +55,4 @@ This method always returns `0` when executed on a JSON type that is not an objec
 ## Version history
 
 - Added in version 1.0.0.
+- Extended template `KeyType` to support any comparable type in version 3.11.0.
diff --git a/doc/mkdocs/docs/api/basic_json/default_object_comparator_t.md b/doc/mkdocs/docs/api/basic_json/default_object_comparator_t.md
index 97b0354223..265a9d385f 100644
--- a/doc/mkdocs/docs/api/basic_json/default_object_comparator_t.md
+++ b/doc/mkdocs/docs/api/basic_json/default_object_comparator_t.md
@@ -15,4 +15,4 @@ The actual comparator used depends on [`object_t`](object_t.md) and can be obtai
 
 ## Version history
 
-- Added in version 3.10.6.
+- Added in version 3.11.0.
diff --git a/doc/mkdocs/docs/api/basic_json/erase.md b/doc/mkdocs/docs/api/basic_json/erase.md
index d94c25b7fd..f377605f56 100644
--- a/doc/mkdocs/docs/api/basic_json/erase.md
+++ b/doc/mkdocs/docs/api/basic_json/erase.md
@@ -10,7 +10,8 @@ iterator erase(iterator first, iterator last);
 const_iterator erase(const_iterator first, const_iterator last);
 
 // (3)
-size_type erase(const typename object_t::key_type& key);
+template<typename KeyType>
+size_type erase(const KeyType& key);
 
 // (4)
 void erase(const size_type idx);
@@ -31,6 +32,13 @@ void erase(const size_type idx);
 
 4. Removes an element from a JSON array by index.
 
+## Template parameters
+
+`KeyType`
+:   A type for an object key other than [`json_pointer`](../json_pointer/index.md) that is comparable with [`string_t`](string_t.md)
+    using [`object_comparator_t`](object_comparator_t.md).
+    This can also be a string literal or a string view (C++17).
+
 ## Parameters
 
 `pos` (in)
@@ -174,3 +182,4 @@ Strong exception safety: if an exception occurs, the original value stays intact
 
 - Added in version 1.0.0.
 - Added support for binary types in version 3.8.0.
+- Added `KeyType` template in version 3.11.0.
diff --git a/doc/mkdocs/docs/api/basic_json/find.md b/doc/mkdocs/docs/api/basic_json/find.md
index af4cb29720..5376011671 100644
--- a/doc/mkdocs/docs/api/basic_json/find.md
+++ b/doc/mkdocs/docs/api/basic_json/find.md
@@ -1,11 +1,11 @@
 # <small>nlohmann::basic_json::</small>find
 
 ```cpp
-template<typename KeyT>
-iterator find(KeyT&& key);
+template<typename KeyType>
+iterator find(const KeyType& key);
 
-template<typename KeyT>
-const_iterator find(KeyT&& key) const;
+template<typename KeyType>
+const_iterator find(const KeyType& key) const;
 ```
 
 Finds an element in a JSON object with key equivalent to `key`. If the element is not found or the JSON value is not an
@@ -13,8 +13,10 @@ object, `end()` is returned.
 
 ## Template parameters
 
-`KeyT`
-:   A type for an object key.
+`KeyType`
+:   A type for an object key other than [`json_pointer`](../json_pointer/index.md) that is comparable with [`string_t`](string_t.md)
+    using [`object_comparator_t`](object_comparator_t.md).
+    This can also be a string literal or a string view (C++17).
 
 ## Parameters
 
@@ -61,3 +63,4 @@ This method always returns `end()` when executed on a JSON type that is not an o
 ## Version history
 
 - Added in version 1.0.0.
+- Extended template `KeyType` to support any comparable type and changed from rvalue reference to const lvalue reference in version 3.11.0.
diff --git a/doc/mkdocs/docs/api/basic_json/operator[].md b/doc/mkdocs/docs/api/basic_json/operator[].md
index 5b6512a21c..4e20d15244 100644
--- a/doc/mkdocs/docs/api/basic_json/operator[].md
+++ b/doc/mkdocs/docs/api/basic_json/operator[].md
@@ -6,12 +6,10 @@ reference operator[](size_type idx);
 const_reference operator[](size_type idx) const;
 
 // (2)
-reference operator[](const typename object_t::key_type& key);
-const_reference operator[](const typename object_t::key_type& key) const;
-template<typename T>
-reference operator[](T* key);
-template<typename T>
-const_reference operator[](T* key) const;
+template<typename KeyType>
+reference operator[](KeyType && key);
+template<typename KeyType>
+const_reference operator[](KeyType && key) const;
 
 // (3)
 reference operator[](const json_pointer& ptr);
@@ -19,13 +17,15 @@ const_reference operator[](const json_pointer& ptr) const;
 ```
 
 1. Returns a reference to the array element at specified location `idx`.
-2. Returns a reference to the object element at with specified key `key`.
-3. Returns a reference to the element at with specified JSON pointer `ptr`.
+2. Returns a reference to the object element with specified key `key`.
+3. Returns a reference to the element with specified JSON pointer `ptr`.
 
 ## Template parameters
 
-`T`
-:   string literal convertible to `object_t::key_type`
+`KeyType`
+:   A type for an object key other than [`json_pointer`](../json_pointer/index.md) that is comparable with [`string_t`](string_t.md)
+    using [`object_comparator_t`](object_comparator_t.md).
+    This can also be a string literal or a string view (C++17).
 
 ## Parameters
 
@@ -192,5 +192,6 @@ Strong exception safety: if an exception occurs, the original value stays intact
 ## Version history
 
 1. Added in version 1.0.0.
-2. Added in version 1.0.0. Overloads for `T* key` added in version 1.1.0.
+2. Added in version 1.0.0. Overloads for `T* key` added in version 1.1.0. Template `T* key` replaced by template `KeyType`
+   in version 3.11.0 which now also supports `std::string_view`.
 3. Added in version 2.0.0.
diff --git a/doc/mkdocs/docs/api/basic_json/value.md b/doc/mkdocs/docs/api/basic_json/value.md
index 0b4f1cc19a..003d86cbd7 100644
--- a/doc/mkdocs/docs/api/basic_json/value.md
+++ b/doc/mkdocs/docs/api/basic_json/value.md
@@ -2,9 +2,9 @@
 
 ```cpp
 // (1)
-template<class ValueType>
-ValueType value(const typename object_t::key_type& key,
-                const ValueType& default_value) const;
+template<class KeyType, class ValueType>
+ValueType value(const KeyType& key,
+                ValueType && default_value) const;
 
 // (2)
 template<class ValueType>
@@ -44,6 +44,10 @@ ValueType value(const json_pointer& ptr,
 
 ## Template parameters
 
+`KeyType`
+:   A type for an object key other than [`json_pointer`](../json_pointer/index.md) that is comparable with [`string_t`](string_t.md)
+    using [`object_comparator_t`](object_comparator_t.md).
+    This can also be a string literal or a string view (C++17).
 `ValueType` 
 :   type compatible to JSON values, for instance `#!cpp int` for JSON integer numbers, `#!cpp bool` for JSON booleans,
     or `#!cpp std::vector` types for JSON arrays. Note the type of the expected value at `key`/`ptr` and the default
@@ -125,5 +129,5 @@ changes to any JSON value.
 
 ## Version history
 
-1. Added in version 1.0.0.
+1. Added in version 1.0.0. Added `KeyType` template parameter in 3.11.0.
 2. Added in version 2.0.2.
diff --git a/include/nlohmann/json.hpp b/include/nlohmann/json.hpp
index ba94d4e3f8..61b0e5e5c9 100644
--- a/include/nlohmann/json.hpp
+++ b/include/nlohmann/json.hpp
@@ -2006,22 +2006,38 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     reference at(const typename object_t::key_type& key)
     {
         // at only works for objects
-        if (JSON_HEDLEY_LIKELY(is_object()))
+        if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
-            JSON_TRY
-            {
-                return set_parent(m_value.object->at(key));
-            }
-            JSON_CATCH (std::out_of_range&)
-            {
-                // create better exception explanation
-                JSON_THROW(out_of_range::create(403, detail::concat("key '", key, "' not found"), this));
-            }
+            JSON_THROW(type_error::create(304, detail::concat("cannot use at() with ", type_name()), this));
         }
-        else
+
+        auto it = m_value.object->find(key);
+        if (it == m_value.object->end())
+        {
+            JSON_THROW(out_of_range::create(403, detail::concat("key '", key, "' not found"), this));
+        }
+        return set_parent(it->second);
+    }
+
+    /// @brief access specified object element with bounds checking
+    /// @sa https://json.nlohmann.me/api/basic_json/at/
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType>::value, int> = 0 >
+    reference at(KeyType && key)
+    {
+        // at only works for objects
+        if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
             JSON_THROW(type_error::create(304, detail::concat("cannot use at() with ", type_name()), this));
         }
+
+        auto it = m_value.object->find(std::forward<KeyType>(key));
+        if (it == m_value.object->end())
+        {
+            // should key be forwarded here? (might call move ctor)
+            JSON_THROW(out_of_range::create(403, detail::concat("key '", string_t(key), "' not found"), this));
+        }
+        return set_parent(it->second);
     }
 
     /// @brief access specified object element with bounds checking
@@ -2029,22 +2045,37 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     const_reference at(const typename object_t::key_type& key) const
     {
         // at only works for objects
-        if (JSON_HEDLEY_LIKELY(is_object()))
+        if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
-            JSON_TRY
-            {
-                return m_value.object->at(key);
-            }
-            JSON_CATCH (std::out_of_range&)
-            {
-                // create better exception explanation
-                JSON_THROW(out_of_range::create(403, detail::concat("key '", key, "' not found"), this));
-            }
+            JSON_THROW(type_error::create(304, detail::concat("cannot use at() with ", type_name()), this));
         }
-        else
+
+        auto it = m_value.object->find(key);
+        if (it == m_value.object->end())
+        {
+            JSON_THROW(out_of_range::create(403, detail::concat("key '", string_t(key), "' not found"), this));
+        }
+        return it->second;
+    }
+
+    /// @brief access specified object element with bounds checking
+    /// @sa https://json.nlohmann.me/api/basic_json/at/
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType>::value, int> = 0 >
+    const_reference at(KeyType && key) const
+    {
+        // at only works for objects
+        if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
             JSON_THROW(type_error::create(304, detail::concat("cannot use at() with ", type_name()), this));
         }
+
+        auto it = m_value.object->find(std::forward<KeyType>(key));
+        if (it == m_value.object->end())
+        {
+            JSON_THROW(out_of_range::create(403, detail::concat("key '", string_t(key), "' not found"), this));
+        }
+        return it->second;
     }
 
     /// @brief access specified array element
@@ -2108,7 +2139,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief access specified object element
     /// @sa https://json.nlohmann.me/api/basic_json/operator%5B%5D/
-    reference operator[](const typename object_t::key_type& key)
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType, true>::value, int> = 0 >
+    reference operator[](KeyType && key)
     {
         // implicitly convert null value to an empty object
         if (is_null())
@@ -2121,7 +2154,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         // operator[] only works for objects
         if (JSON_HEDLEY_LIKELY(is_object()))
         {
-            return set_parent(m_value.object->operator[](key));
+            auto result = m_value.object->emplace(std::forward<KeyType>(key), nullptr);
+            return set_parent(result.first->second);
         }
 
         JSON_THROW(type_error::create(305, detail::concat("cannot use operator[] with a string argument with ", type_name()), this));
@@ -2129,13 +2163,16 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief access specified object element
     /// @sa https://json.nlohmann.me/api/basic_json/operator%5B%5D/
-    const_reference operator[](const typename object_t::key_type& key) const
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType, true>::value, int> = 0 >
+    const_reference operator[](KeyType && key) const
     {
         // const operator[] only works for objects
         if (JSON_HEDLEY_LIKELY(is_object()))
         {
-            JSON_ASSERT(m_value.object->find(key) != m_value.object->end());
-            return m_value.object->find(key)->second;
+            auto it = m_value.object->find(std::forward<KeyType>(key));
+            JSON_ASSERT(it != m_value.object->end());
+            return it->second;
         }
 
         JSON_THROW(type_error::create(305, detail::concat("cannot use operator[] with a string argument with ", type_name()), this));
@@ -2155,7 +2192,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             assert_invariant();
         }
 
-        // at only works for objects
+        // operator[] only works for objects
         if (JSON_HEDLEY_LIKELY(is_object()))
         {
             return set_parent(m_value.object->operator[](key));
@@ -2170,7 +2207,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     JSON_HEDLEY_NON_NULL(2)
     const_reference operator[](T* key) const
     {
-        // at only works for objects
+        // operator[] only works for objects
         if (JSON_HEDLEY_LIKELY(is_object()))
         {
             JSON_ASSERT(m_value.object->find(key) != m_value.object->end());
@@ -2183,22 +2220,23 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @brief access specified object element with default value
     /// @sa https://json.nlohmann.me/api/basic_json/value/
     /// using std::is_convertible in a std::enable_if will fail when using explicit conversions
-    template < class ValueType, typename std::enable_if <
+    template < class KeyType, class ValueType, detail::enable_if_t <
                    detail::is_getable<basic_json_t, ValueType>::value
-                   && !std::is_same<value_t, ValueType>::value, int >::type = 0 >
-    ValueType value(const typename object_t::key_type& key, const ValueType& default_value) const
+                   && !std::is_same<value_t, ValueType>::value
+                   && !detail::is_json_pointer<KeyType>::value, int > = 0 >
+    typename std::decay<ValueType>::type value(KeyType && key, ValueType && default_value) const
     {
-        // at only works for objects
+        // value only works for objects
         if (JSON_HEDLEY_LIKELY(is_object()))
         {
             // if key is found, return value and given default value otherwise
-            const auto it = find(key);
+            const auto it = find(std::forward<KeyType>(key));
             if (it != end())
             {
-                return it->template get<ValueType>();
+                return it->template get<typename std::decay<ValueType>::type>();
             }
 
-            return default_value;
+            return std::forward<ValueType>(default_value);
         }
 
         JSON_THROW(type_error::create(306, detail::concat("cannot use value() with ", type_name()), this));
@@ -2207,18 +2245,20 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @brief access specified object element with default value
     /// @sa https://json.nlohmann.me/api/basic_json/value/
     /// overload for a default value of type const char*
-    string_t value(const typename object_t::key_type& key, const char* default_value) const
+    template < class KeyType, detail::enable_if_t <
+                   !detail::is_json_pointer<KeyType>::value, int > = 0 >
+    string_t value(KeyType && key, const char* default_value) const
     {
-        return value(key, string_t(default_value));
+        return value(std::forward<KeyType>(key), string_t(default_value));
     }
 
     /// @brief access specified object element via JSON Pointer with default value
     /// @sa https://json.nlohmann.me/api/basic_json/value/
-    template<class ValueType, typename std::enable_if<
-                 detail::is_getable<basic_json_t, ValueType>::value, int>::type = 0>
+    template < class ValueType, detail::enable_if_t <
+                   detail::is_getable<basic_json_t, ValueType>::value, int> = 0 >
     ValueType value(const json_pointer& ptr, const ValueType& default_value) const
     {
-        // at only works for objects
+        // value only works for objects
         if (JSON_HEDLEY_LIKELY(is_object()))
         {
             // if pointer resolves a value, return it or use default value
@@ -2235,8 +2275,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         JSON_THROW(type_error::create(306, detail::concat("cannot use value() with ", type_name()), this));
     }
 
-    template<class ValueType, class BasicJsonType, typename std::enable_if<
-                 detail::is_getable<basic_json_t, ValueType>::value, int>::type = 0>
+    template < class ValueType, class BasicJsonType, detail::enable_if_t <
+                   detail::is_getable<basic_json_t, ValueType>::value, int> = 0 >
     JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
     ValueType value(const ::nlohmann::json_pointer<BasicJsonType>& ptr, const ValueType& default_value) const
     {
@@ -2294,10 +2334,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief remove element given an iterator
     /// @sa https://json.nlohmann.me/api/basic_json/erase/
-    template < class IteratorType, typename std::enable_if <
+    template < class IteratorType, detail::enable_if_t <
                    std::is_same<IteratorType, typename basic_json_t::iterator>::value ||
-                   std::is_same<IteratorType, typename basic_json_t::const_iterator>::value, int >::type
-               = 0 >
+                   std::is_same<IteratorType, typename basic_json_t::const_iterator>::value, int > = 0 >
     IteratorType erase(IteratorType pos)
     {
         // make sure iterator fits the current value
@@ -2365,10 +2404,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief remove elements given an iterator range
     /// @sa https://json.nlohmann.me/api/basic_json/erase/
-    template < class IteratorType, typename std::enable_if <
+    template < class IteratorType, detail::enable_if_t <
                    std::is_same<IteratorType, typename basic_json_t::iterator>::value ||
-                   std::is_same<IteratorType, typename basic_json_t::const_iterator>::value, int >::type
-               = 0 >
+                   std::is_same<IteratorType, typename basic_json_t::const_iterator>::value, int > = 0 >
     IteratorType erase(IteratorType first, IteratorType last)
     {
         // make sure iterator fits the current value
@@ -2437,17 +2475,57 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         return result;
     }
 
-    /// @brief remove element from a JSON object given a key
-    /// @sa https://json.nlohmann.me/api/basic_json/erase/
-    size_type erase(const typename object_t::key_type& key)
+  private:
+    template < typename KeyType, detail::enable_if_t <
+                   detail::has_erase_with_key_type<basic_json_t, KeyType>::value, int > = 0 >
+    size_type erase_internal(KeyType && key)
     {
         // this erase only works for objects
-        if (JSON_HEDLEY_LIKELY(is_object()))
+        if (JSON_HEDLEY_UNLIKELY(!is_object()))
+        {
+            JSON_THROW(type_error::create(307, detail::concat("cannot use erase() with ", type_name()), this));
+        }
+
+        return m_value.object->erase(std::forward<KeyType>(key));
+    }
+
+    template < typename KeyType, detail::enable_if_t <
+                   !detail::has_erase_with_key_type<basic_json_t, KeyType>::value, int > = 0 >
+    size_type erase_internal(KeyType && key)
+    {
+        // this erase only works for objects
+        if (JSON_HEDLEY_UNLIKELY(!is_object()))
+        {
+            JSON_THROW(type_error::create(307, detail::concat("cannot use erase() with ", type_name()), this));
+        }
+
+        const auto it = m_value.object->find(std::forward<KeyType>(key));
+        if (it != m_value.object->end())
         {
-            return m_value.object->erase(key);
+            m_value.object->erase(it);
+            return 1;
         }
+        return 0;
+    }
+
+  public:
 
-        JSON_THROW(type_error::create(307, detail::concat("cannot use erase() with ", type_name()), this));
+    /// @brief remove element from a JSON object given a key
+    /// @sa https://json.nlohmann.me/api/basic_json/erase/
+    size_type erase(const typename object_t::key_type& key)
+    {
+        // the indirection via erase_internal() is needed to avoid making this
+        // function a template and thus de-rank it during overload resolution
+        return erase_internal(key);
+    }
+
+    /// @brief remove element from a JSON object given a key
+    /// @sa https://json.nlohmann.me/api/basic_json/erase/
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType>::value, int > = 0 >
+    size_type erase(KeyType && key)
+    {
+        return erase_internal(std::forward<KeyType>(key));
     }
 
     /// @brief remove element from a JSON array given an index
@@ -2482,14 +2560,41 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief find an element in a JSON object
     /// @sa https://json.nlohmann.me/api/basic_json/find/
-    template<typename KeyT>
-    iterator find(KeyT&& key)
+    iterator find(const typename object_t::key_type& key)
+    {
+        auto result = end();
+
+        if (is_object())
+        {
+            result.m_it.object_iterator = m_value.object->find(key);
+        }
+
+        return result;
+    }
+
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType>::value, int> = 0>
+    iterator find(KeyType && key)
     {
         auto result = end();
 
         if (is_object())
         {
-            result.m_it.object_iterator = m_value.object->find(std::forward<KeyT>(key));
+            result.m_it.object_iterator = m_value.object->find(std::forward<KeyType>(key));
+        }
+
+        return result;
+    }
+
+    /// @brief find an element in a JSON object
+    /// @sa https://json.nlohmann.me/api/basic_json/find/
+    const_iterator find(const typename object_t::key_type& key) const
+    {
+        auto result = cend();
+
+        if (is_object())
+        {
+            result.m_it.object_iterator = m_value.object->find(key);
         }
 
         return result;
@@ -2497,14 +2602,15 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief find an element in a JSON object
     /// @sa https://json.nlohmann.me/api/basic_json/find/
-    template<typename KeyT>
-    const_iterator find(KeyT&& key) const
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType>::value, int> = 0 >
+    const_iterator find(KeyType && key) const
     {
         auto result = cend();
 
         if (is_object())
         {
-            result.m_it.object_iterator = m_value.object->find(std::forward<KeyT>(key));
+            result.m_it.object_iterator = m_value.object->find(std::forward<KeyType>(key));
         }
 
         return result;
@@ -2512,20 +2618,36 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief returns the number of occurrences of a key in a JSON object
     /// @sa https://json.nlohmann.me/api/basic_json/count/
-    template<typename KeyT>
-    size_type count(KeyT&& key) const
+    size_type count(const typename object_t::key_type& key) const
     {
         // return 0 for all nonobject types
-        return is_object() ? m_value.object->count(std::forward<KeyT>(key)) : 0;
+        return is_object() ? m_value.object->count(key) : 0;
+    }
+
+    /// @brief returns the number of occurrences of a key in a JSON object
+    /// @sa https://json.nlohmann.me/api/basic_json/count/
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType>::value, int> = 0 >
+    size_type count(KeyType && key) const
+    {
+        // return 0 for all nonobject types
+        return is_object() ? m_value.object->count(std::forward<KeyType>(key)) : 0;
+    }
+
+    /// @brief check the existence of an element in a JSON object
+    /// @sa https://json.nlohmann.me/api/basic_json/contains/
+    bool contains(const typename object_t::key_type& key) const
+    {
+        return is_object() && m_value.object->find(key) != m_value.object->end();
     }
 
     /// @brief check the existence of an element in a JSON object
     /// @sa https://json.nlohmann.me/api/basic_json/contains/
-    template < typename KeyT, typename std::enable_if <
-                   !detail::is_json_pointer<typename std::decay<KeyT>::type>::value, int >::type = 0 >
-    bool contains(KeyT && key) const
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType>::value, int> = 0 >
+    bool contains(KeyType && key) const
     {
-        return is_object() && m_value.object->find(std::forward<KeyT>(key)) != m_value.object->end();
+        return is_object() && m_value.object->find(std::forward<KeyType>(key)) != m_value.object->end();
     }
 
     /// @brief check the existence of an element in a JSON object given a JSON pointer
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 0967c48797..e64ff40329 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -19546,22 +19546,38 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     reference at(const typename object_t::key_type& key)
     {
         // at only works for objects
-        if (JSON_HEDLEY_LIKELY(is_object()))
+        if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
-            JSON_TRY
-            {
-                return set_parent(m_value.object->at(key));
-            }
-            JSON_CATCH (std::out_of_range&)
-            {
-                // create better exception explanation
-                JSON_THROW(out_of_range::create(403, detail::concat("key '", key, "' not found"), this));
-            }
+            JSON_THROW(type_error::create(304, detail::concat("cannot use at() with ", type_name()), this));
         }
-        else
+
+        auto it = m_value.object->find(key);
+        if (it == m_value.object->end())
+        {
+            JSON_THROW(out_of_range::create(403, detail::concat("key '", key, "' not found"), this));
+        }
+        return set_parent(it->second);
+    }
+
+    /// @brief access specified object element with bounds checking
+    /// @sa https://json.nlohmann.me/api/basic_json/at/
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType>::value, int> = 0 >
+    reference at(KeyType && key)
+    {
+        // at only works for objects
+        if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
             JSON_THROW(type_error::create(304, detail::concat("cannot use at() with ", type_name()), this));
         }
+
+        auto it = m_value.object->find(std::forward<KeyType>(key));
+        if (it == m_value.object->end())
+        {
+            // should key be forwarded here? (might call move ctor)
+            JSON_THROW(out_of_range::create(403, detail::concat("key '", string_t(key), "' not found"), this));
+        }
+        return set_parent(it->second);
     }
 
     /// @brief access specified object element with bounds checking
@@ -19569,22 +19585,37 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     const_reference at(const typename object_t::key_type& key) const
     {
         // at only works for objects
-        if (JSON_HEDLEY_LIKELY(is_object()))
+        if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
-            JSON_TRY
-            {
-                return m_value.object->at(key);
-            }
-            JSON_CATCH (std::out_of_range&)
-            {
-                // create better exception explanation
-                JSON_THROW(out_of_range::create(403, detail::concat("key '", key, "' not found"), this));
-            }
+            JSON_THROW(type_error::create(304, detail::concat("cannot use at() with ", type_name()), this));
         }
-        else
+
+        auto it = m_value.object->find(key);
+        if (it == m_value.object->end())
+        {
+            JSON_THROW(out_of_range::create(403, detail::concat("key '", string_t(key), "' not found"), this));
+        }
+        return it->second;
+    }
+
+    /// @brief access specified object element with bounds checking
+    /// @sa https://json.nlohmann.me/api/basic_json/at/
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType>::value, int> = 0 >
+    const_reference at(KeyType && key) const
+    {
+        // at only works for objects
+        if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
             JSON_THROW(type_error::create(304, detail::concat("cannot use at() with ", type_name()), this));
         }
+
+        auto it = m_value.object->find(std::forward<KeyType>(key));
+        if (it == m_value.object->end())
+        {
+            JSON_THROW(out_of_range::create(403, detail::concat("key '", string_t(key), "' not found"), this));
+        }
+        return it->second;
     }
 
     /// @brief access specified array element
@@ -19648,7 +19679,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief access specified object element
     /// @sa https://json.nlohmann.me/api/basic_json/operator%5B%5D/
-    reference operator[](const typename object_t::key_type& key)
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType, true>::value, int> = 0 >
+    reference operator[](KeyType && key)
     {
         // implicitly convert null value to an empty object
         if (is_null())
@@ -19661,7 +19694,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         // operator[] only works for objects
         if (JSON_HEDLEY_LIKELY(is_object()))
         {
-            return set_parent(m_value.object->operator[](key));
+            auto result = m_value.object->emplace(std::forward<KeyType>(key), nullptr);
+            return set_parent(result.first->second);
         }
 
         JSON_THROW(type_error::create(305, detail::concat("cannot use operator[] with a string argument with ", type_name()), this));
@@ -19669,13 +19703,16 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief access specified object element
     /// @sa https://json.nlohmann.me/api/basic_json/operator%5B%5D/
-    const_reference operator[](const typename object_t::key_type& key) const
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType, true>::value, int> = 0 >
+    const_reference operator[](KeyType && key) const
     {
         // const operator[] only works for objects
         if (JSON_HEDLEY_LIKELY(is_object()))
         {
-            JSON_ASSERT(m_value.object->find(key) != m_value.object->end());
-            return m_value.object->find(key)->second;
+            auto it = m_value.object->find(std::forward<KeyType>(key));
+            JSON_ASSERT(it != m_value.object->end());
+            return it->second;
         }
 
         JSON_THROW(type_error::create(305, detail::concat("cannot use operator[] with a string argument with ", type_name()), this));
@@ -19695,7 +19732,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             assert_invariant();
         }
 
-        // at only works for objects
+        // operator[] only works for objects
         if (JSON_HEDLEY_LIKELY(is_object()))
         {
             return set_parent(m_value.object->operator[](key));
@@ -19710,7 +19747,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     JSON_HEDLEY_NON_NULL(2)
     const_reference operator[](T* key) const
     {
-        // at only works for objects
+        // operator[] only works for objects
         if (JSON_HEDLEY_LIKELY(is_object()))
         {
             JSON_ASSERT(m_value.object->find(key) != m_value.object->end());
@@ -19723,22 +19760,23 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @brief access specified object element with default value
     /// @sa https://json.nlohmann.me/api/basic_json/value/
     /// using std::is_convertible in a std::enable_if will fail when using explicit conversions
-    template < class ValueType, typename std::enable_if <
+    template < class KeyType, class ValueType, detail::enable_if_t <
                    detail::is_getable<basic_json_t, ValueType>::value
-                   && !std::is_same<value_t, ValueType>::value, int >::type = 0 >
-    ValueType value(const typename object_t::key_type& key, const ValueType& default_value) const
+                   && !std::is_same<value_t, ValueType>::value
+                   && !detail::is_json_pointer<KeyType>::value, int > = 0 >
+    typename std::decay<ValueType>::type value(KeyType && key, ValueType && default_value) const
     {
-        // at only works for objects
+        // value only works for objects
         if (JSON_HEDLEY_LIKELY(is_object()))
         {
             // if key is found, return value and given default value otherwise
-            const auto it = find(key);
+            const auto it = find(std::forward<KeyType>(key));
             if (it != end())
             {
-                return it->template get<ValueType>();
+                return it->template get<typename std::decay<ValueType>::type>();
             }
 
-            return default_value;
+            return std::forward<ValueType>(default_value);
         }
 
         JSON_THROW(type_error::create(306, detail::concat("cannot use value() with ", type_name()), this));
@@ -19747,18 +19785,20 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @brief access specified object element with default value
     /// @sa https://json.nlohmann.me/api/basic_json/value/
     /// overload for a default value of type const char*
-    string_t value(const typename object_t::key_type& key, const char* default_value) const
+    template < class KeyType, detail::enable_if_t <
+                   !detail::is_json_pointer<KeyType>::value, int > = 0 >
+    string_t value(KeyType && key, const char* default_value) const
     {
-        return value(key, string_t(default_value));
+        return value(std::forward<KeyType>(key), string_t(default_value));
     }
 
     /// @brief access specified object element via JSON Pointer with default value
     /// @sa https://json.nlohmann.me/api/basic_json/value/
-    template<class ValueType, typename std::enable_if<
-                 detail::is_getable<basic_json_t, ValueType>::value, int>::type = 0>
+    template < class ValueType, detail::enable_if_t <
+                   detail::is_getable<basic_json_t, ValueType>::value, int> = 0 >
     ValueType value(const json_pointer& ptr, const ValueType& default_value) const
     {
-        // at only works for objects
+        // value only works for objects
         if (JSON_HEDLEY_LIKELY(is_object()))
         {
             // if pointer resolves a value, return it or use default value
@@ -19775,8 +19815,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         JSON_THROW(type_error::create(306, detail::concat("cannot use value() with ", type_name()), this));
     }
 
-    template<class ValueType, class BasicJsonType, typename std::enable_if<
-                 detail::is_getable<basic_json_t, ValueType>::value, int>::type = 0>
+    template < class ValueType, class BasicJsonType, detail::enable_if_t <
+                   detail::is_getable<basic_json_t, ValueType>::value, int> = 0 >
     JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
     ValueType value(const ::nlohmann::json_pointer<BasicJsonType>& ptr, const ValueType& default_value) const
     {
@@ -19834,10 +19874,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief remove element given an iterator
     /// @sa https://json.nlohmann.me/api/basic_json/erase/
-    template < class IteratorType, typename std::enable_if <
+    template < class IteratorType, detail::enable_if_t <
                    std::is_same<IteratorType, typename basic_json_t::iterator>::value ||
-                   std::is_same<IteratorType, typename basic_json_t::const_iterator>::value, int >::type
-               = 0 >
+                   std::is_same<IteratorType, typename basic_json_t::const_iterator>::value, int > = 0 >
     IteratorType erase(IteratorType pos)
     {
         // make sure iterator fits the current value
@@ -19905,10 +19944,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief remove elements given an iterator range
     /// @sa https://json.nlohmann.me/api/basic_json/erase/
-    template < class IteratorType, typename std::enable_if <
+    template < class IteratorType, detail::enable_if_t <
                    std::is_same<IteratorType, typename basic_json_t::iterator>::value ||
-                   std::is_same<IteratorType, typename basic_json_t::const_iterator>::value, int >::type
-               = 0 >
+                   std::is_same<IteratorType, typename basic_json_t::const_iterator>::value, int > = 0 >
     IteratorType erase(IteratorType first, IteratorType last)
     {
         // make sure iterator fits the current value
@@ -19977,17 +20015,57 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         return result;
     }
 
-    /// @brief remove element from a JSON object given a key
-    /// @sa https://json.nlohmann.me/api/basic_json/erase/
-    size_type erase(const typename object_t::key_type& key)
+  private:
+    template < typename KeyType, detail::enable_if_t <
+                   detail::has_erase_with_key_type<basic_json_t, KeyType>::value, int > = 0 >
+    size_type erase_internal(KeyType && key)
     {
         // this erase only works for objects
-        if (JSON_HEDLEY_LIKELY(is_object()))
+        if (JSON_HEDLEY_UNLIKELY(!is_object()))
+        {
+            JSON_THROW(type_error::create(307, detail::concat("cannot use erase() with ", type_name()), this));
+        }
+
+        return m_value.object->erase(std::forward<KeyType>(key));
+    }
+
+    template < typename KeyType, detail::enable_if_t <
+                   !detail::has_erase_with_key_type<basic_json_t, KeyType>::value, int > = 0 >
+    size_type erase_internal(KeyType && key)
+    {
+        // this erase only works for objects
+        if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
-            return m_value.object->erase(key);
+            JSON_THROW(type_error::create(307, detail::concat("cannot use erase() with ", type_name()), this));
         }
 
-        JSON_THROW(type_error::create(307, detail::concat("cannot use erase() with ", type_name()), this));
+        const auto it = m_value.object->find(std::forward<KeyType>(key));
+        if (it != m_value.object->end())
+        {
+            m_value.object->erase(it);
+            return 1;
+        }
+        return 0;
+    }
+
+  public:
+
+    /// @brief remove element from a JSON object given a key
+    /// @sa https://json.nlohmann.me/api/basic_json/erase/
+    size_type erase(const typename object_t::key_type& key)
+    {
+        // the indirection via erase_internal() is needed to avoid making this
+        // function a template and thus de-rank it during overload resolution
+        return erase_internal(key);
+    }
+
+    /// @brief remove element from a JSON object given a key
+    /// @sa https://json.nlohmann.me/api/basic_json/erase/
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType>::value, int > = 0 >
+    size_type erase(KeyType && key)
+    {
+        return erase_internal(std::forward<KeyType>(key));
     }
 
     /// @brief remove element from a JSON array given an index
@@ -20022,14 +20100,41 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief find an element in a JSON object
     /// @sa https://json.nlohmann.me/api/basic_json/find/
-    template<typename KeyT>
-    iterator find(KeyT&& key)
+    iterator find(const typename object_t::key_type& key)
     {
         auto result = end();
 
         if (is_object())
         {
-            result.m_it.object_iterator = m_value.object->find(std::forward<KeyT>(key));
+            result.m_it.object_iterator = m_value.object->find(key);
+        }
+
+        return result;
+    }
+
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType>::value, int> = 0>
+    iterator find(KeyType && key)
+    {
+        auto result = end();
+
+        if (is_object())
+        {
+            result.m_it.object_iterator = m_value.object->find(std::forward<KeyType>(key));
+        }
+
+        return result;
+    }
+
+    /// @brief find an element in a JSON object
+    /// @sa https://json.nlohmann.me/api/basic_json/find/
+    const_iterator find(const typename object_t::key_type& key) const
+    {
+        auto result = cend();
+
+        if (is_object())
+        {
+            result.m_it.object_iterator = m_value.object->find(key);
         }
 
         return result;
@@ -20037,14 +20142,15 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief find an element in a JSON object
     /// @sa https://json.nlohmann.me/api/basic_json/find/
-    template<typename KeyT>
-    const_iterator find(KeyT&& key) const
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType>::value, int> = 0 >
+    const_iterator find(KeyType && key) const
     {
         auto result = cend();
 
         if (is_object())
         {
-            result.m_it.object_iterator = m_value.object->find(std::forward<KeyT>(key));
+            result.m_it.object_iterator = m_value.object->find(std::forward<KeyType>(key));
         }
 
         return result;
@@ -20052,20 +20158,36 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief returns the number of occurrences of a key in a JSON object
     /// @sa https://json.nlohmann.me/api/basic_json/count/
-    template<typename KeyT>
-    size_type count(KeyT&& key) const
+    size_type count(const typename object_t::key_type& key) const
     {
         // return 0 for all nonobject types
-        return is_object() ? m_value.object->count(std::forward<KeyT>(key)) : 0;
+        return is_object() ? m_value.object->count(key) : 0;
+    }
+
+    /// @brief returns the number of occurrences of a key in a JSON object
+    /// @sa https://json.nlohmann.me/api/basic_json/count/
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType>::value, int> = 0 >
+    size_type count(KeyType && key) const
+    {
+        // return 0 for all nonobject types
+        return is_object() ? m_value.object->count(std::forward<KeyType>(key)) : 0;
+    }
+
+    /// @brief check the existence of an element in a JSON object
+    /// @sa https://json.nlohmann.me/api/basic_json/contains/
+    bool contains(const typename object_t::key_type& key) const
+    {
+        return is_object() && m_value.object->find(key) != m_value.object->end();
     }
 
     /// @brief check the existence of an element in a JSON object
     /// @sa https://json.nlohmann.me/api/basic_json/contains/
-    template < typename KeyT, typename std::enable_if <
-                   !detail::is_json_pointer<typename std::decay<KeyT>::type>::value, int >::type = 0 >
-    bool contains(KeyT && key) const
+    template < class KeyType, detail::enable_if_t <
+                   detail::is_usable_as_key_type<basic_json_t, KeyType>::value, int> = 0 >
+    bool contains(KeyType && key) const
     {
-        return is_object() && m_value.object->find(std::forward<KeyT>(key)) != m_value.object->end();
+        return is_object() && m_value.object->find(std::forward<KeyType>(key)) != m_value.object->end();
     }
 
     /// @brief check the existence of an element in a JSON object given a JSON pointer
diff --git a/test/src/unit-element_access2.cpp b/test/src/unit-element_access2.cpp
index 94e0df42d2..11daba1455 100644
--- a/test/src/unit-element_access2.cpp
+++ b/test/src/unit-element_access2.cpp
@@ -60,12 +60,38 @@ TEST_CASE("element access 2")
                 CHECK(j_const.at("floating") == json(42.23));
                 CHECK(j_const.at("object") == json::object());
                 CHECK(j_const.at("array") == json({1, 2, 3}));
+
+#ifdef JSON_HAS_CPP_17
+                CHECK(j.at(std::string_view("integer")) == json(1));
+                CHECK(j.at(std::string_view("unsigned")) == json(1u));
+                CHECK(j.at(std::string_view("boolean")) == json(true));
+                CHECK(j.at(std::string_view("null")) == json(nullptr));
+                CHECK(j.at(std::string_view("string")) == json("hello world"));
+                CHECK(j.at(std::string_view("floating")) == json(42.23));
+                CHECK(j.at(std::string_view("object")) == json::object());
+                CHECK(j.at(std::string_view("array")) == json({1, 2, 3}));
+
+                CHECK(j_const.at(std::string_view("integer")) == json(1));
+                CHECK(j_const.at(std::string_view("unsigned")) == json(1u));
+                CHECK(j_const.at(std::string_view("boolean")) == json(true));
+                CHECK(j_const.at(std::string_view("null")) == json(nullptr));
+                CHECK(j_const.at(std::string_view("string")) == json("hello world"));
+                CHECK(j_const.at(std::string_view("floating")) == json(42.23));
+                CHECK(j_const.at(std::string_view("object")) == json::object());
+                CHECK(j_const.at(std::string_view("array")) == json({1, 2, 3}));
+#endif
             }
 
             SECTION("access outside bounds")
             {
                 CHECK_THROWS_WITH_AS(j.at("foo"), "[json.exception.out_of_range.403] key 'foo' not found", json::out_of_range&);
                 CHECK_THROWS_WITH_AS(j_const.at("foo"), "[json.exception.out_of_range.403] key 'foo' not found", json::out_of_range&);
+
+
+#ifdef JSON_HAS_CPP_17
+                CHECK_THROWS_WITH_AS(j.at(std::string_view("foo")), "[json.exception.out_of_range.403] key 'foo' not found", json::out_of_range&);
+                CHECK_THROWS_WITH_AS(j_const.at(std::string_view("foo")), "[json.exception.out_of_range.403] key 'foo' not found", json::out_of_range&);
+#endif
             }
 
             SECTION("access on non-object type")
@@ -76,6 +102,11 @@ TEST_CASE("element access 2")
                     const json j_nonobject_const(j_nonobject);
                     CHECK_THROWS_WITH_AS(j_nonobject.at("foo"), "[json.exception.type_error.304] cannot use at() with null", json::type_error&);
                     CHECK_THROWS_WITH_AS(j_nonobject_const.at("foo"), "[json.exception.type_error.304] cannot use at() with null", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject.at(std::string_view(std::string_view("foo"))), "[json.exception.type_error.304] cannot use at() with null", json::type_error&);
+                    CHECK_THROWS_WITH_AS(j_nonobject_const.at(std::string_view(std::string_view("foo"))), "[json.exception.type_error.304] cannot use at() with null", json::type_error&);
+#endif
                 }
 
                 SECTION("boolean")
@@ -84,6 +115,11 @@ TEST_CASE("element access 2")
                     const json j_nonobject_const(j_nonobject);
                     CHECK_THROWS_WITH_AS(j_nonobject.at("foo"), "[json.exception.type_error.304] cannot use at() with boolean", json::type_error&);
                     CHECK_THROWS_WITH_AS(j_nonobject_const.at("foo"), "[json.exception.type_error.304] cannot use at() with boolean", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject.at(std::string_view("foo")), "[json.exception.type_error.304] cannot use at() with boolean", json::type_error&);
+                    CHECK_THROWS_WITH_AS(j_nonobject_const.at(std::string_view("foo")), "[json.exception.type_error.304] cannot use at() with boolean", json::type_error&);
+#endif
                 }
 
                 SECTION("string")
@@ -92,6 +128,11 @@ TEST_CASE("element access 2")
                     const json j_nonobject_const(j_nonobject);
                     CHECK_THROWS_WITH_AS(j_nonobject.at("foo"), "[json.exception.type_error.304] cannot use at() with string", json::type_error&);
                     CHECK_THROWS_WITH_AS(j_nonobject_const.at("foo"), "[json.exception.type_error.304] cannot use at() with string", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject.at(std::string_view("foo")), "[json.exception.type_error.304] cannot use at() with string", json::type_error&);
+                    CHECK_THROWS_WITH_AS(j_nonobject_const.at(std::string_view("foo")), "[json.exception.type_error.304] cannot use at() with string", json::type_error&);
+#endif
                 }
 
                 SECTION("array")
@@ -100,6 +141,11 @@ TEST_CASE("element access 2")
                     const json j_nonobject_const(j_nonobject);
                     CHECK_THROWS_WITH_AS(j_nonobject.at("foo"), "[json.exception.type_error.304] cannot use at() with array", json::type_error&);
                     CHECK_THROWS_WITH_AS(j_nonobject_const.at("foo"), "[json.exception.type_error.304] cannot use at() with array", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject.at(std::string_view("foo")), "[json.exception.type_error.304] cannot use at() with array", json::type_error&);
+                    CHECK_THROWS_WITH_AS(j_nonobject_const.at(std::string_view("foo")), "[json.exception.type_error.304] cannot use at() with array", json::type_error&);
+#endif
                 }
 
                 SECTION("number (integer)")
@@ -108,6 +154,11 @@ TEST_CASE("element access 2")
                     const json j_nonobject_const(j_nonobject);
                     CHECK_THROWS_WITH_AS(j_nonobject.at("foo"), "[json.exception.type_error.304] cannot use at() with number", json::type_error&);
                     CHECK_THROWS_WITH_AS(j_nonobject_const.at("foo"), "[json.exception.type_error.304] cannot use at() with number", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject.at(std::string_view("foo")), "[json.exception.type_error.304] cannot use at() with number", json::type_error&);
+                    CHECK_THROWS_WITH_AS(j_nonobject_const.at(std::string_view("foo")), "[json.exception.type_error.304] cannot use at() with number", json::type_error&);
+#endif
                 }
 
                 SECTION("number (unsigned)")
@@ -116,6 +167,11 @@ TEST_CASE("element access 2")
                     const json j_nonobject_const(j_nonobject);
                     CHECK_THROWS_WITH_AS(j_nonobject.at("foo"), "[json.exception.type_error.304] cannot use at() with number", json::type_error&);
                     CHECK_THROWS_WITH_AS(j_nonobject_const.at("foo"), "[json.exception.type_error.304] cannot use at() with number", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject.at(std::string_view("foo")), "[json.exception.type_error.304] cannot use at() with number", json::type_error&);
+                    CHECK_THROWS_WITH_AS(j_nonobject_const.at(std::string_view("foo")), "[json.exception.type_error.304] cannot use at() with number", json::type_error&);
+#endif
                 }
 
                 SECTION("number (floating-point)")
@@ -124,6 +180,11 @@ TEST_CASE("element access 2")
                     const json j_nonobject_const(j_nonobject);
                     CHECK_THROWS_WITH_AS(j_nonobject.at("foo"), "[json.exception.type_error.304] cannot use at() with number", json::type_error&);
                     CHECK_THROWS_WITH_AS(j_nonobject_const.at("foo"), "[json.exception.type_error.304] cannot use at() with number", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject.at(std::string_view("foo")), "[json.exception.type_error.304] cannot use at() with number", json::type_error&);
+                    CHECK_THROWS_WITH_AS(j_nonobject_const.at(std::string_view("foo")), "[json.exception.type_error.304] cannot use at() with number", json::type_error&);
+#endif
                 }
             }
         }
@@ -158,6 +219,33 @@ TEST_CASE("element access 2")
                     CHECK(j_const.value("floating", 12) == 42);
                     CHECK(j_const.value("object", json({{"foo", "bar"}})) == json::object());
                     CHECK(j_const.value("array", json({10, 100})) == json({1, 2, 3}));
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j.value(std::string_view("integer"), 2) == 1);
+                    CHECK(j.value(std::string_view("integer"), 1.0) == Approx(1));
+                    CHECK(j.value(std::string_view("unsigned"), 2) == 1u);
+                    CHECK(j.value(std::string_view("unsigned"), 1.0) == Approx(1u));
+                    CHECK(j.value(std::string_view("null"), json(1)) == json());
+                    CHECK(j.value(std::string_view("boolean"), false) == true);
+                    CHECK(j.value(std::string_view("string"), "bar") == "hello world");
+                    CHECK(j.value(std::string_view("string"), std::string("bar")) == "hello world");
+                    CHECK(j.value(std::string_view("floating"), 12.34) == Approx(42.23));
+                    CHECK(j.value(std::string_view("floating"), 12) == 42);
+                    CHECK(j.value(std::string_view("object"), json({{"foo", "bar"}})) == json::object());
+                    CHECK(j.value(std::string_view("array"), json({10, 100})) == json({1, 2, 3}));
+
+                    CHECK(j_const.value(std::string_view("integer"), 2) == 1);
+                    CHECK(j_const.value(std::string_view("integer"), 1.0) == Approx(1));
+                    CHECK(j_const.value(std::string_view("unsigned"), 2) == 1u);
+                    CHECK(j_const.value(std::string_view("unsigned"), 1.0) == Approx(1u));
+                    CHECK(j_const.value(std::string_view("boolean"), false) == true);
+                    CHECK(j_const.value(std::string_view("string"), "bar") == "hello world");
+                    CHECK(j_const.value(std::string_view("string"), std::string("bar")) == "hello world");
+                    CHECK(j_const.value(std::string_view("floating"), 12.34) == Approx(42.23));
+                    CHECK(j_const.value(std::string_view("floating"), 12) == 42);
+                    CHECK(j_const.value(std::string_view("object"), json({{"foo", "bar"}})) == json::object());
+                    CHECK(j_const.value(std::string_view("array"), json({10, 100})) == json({1, 2, 3}));
+#endif
                 }
 
                 SECTION("access non-existing value")
@@ -177,6 +265,24 @@ TEST_CASE("element access 2")
                     CHECK(j_const.value("_", 12.34) == Approx(12.34));
                     CHECK(j_const.value("_", json({{"foo", "bar"}})) == json({{"foo", "bar"}}));
                     CHECK(j_const.value("_", json({10, 100})) == json({10, 100}));
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j.value(std::string_view("_"), 2) == 2);
+                    CHECK(j.value(std::string_view("_"), 2u) == 2u);
+                    CHECK(j.value(std::string_view("_"), false) == false);
+                    CHECK(j.value(std::string_view("_"), "bar") == "bar");
+                    CHECK(j.value(std::string_view("_"), 12.34) == Approx(12.34));
+                    CHECK(j.value(std::string_view("_"), json({{"foo", "bar"}})) == json({{"foo", "bar"}}));
+                    CHECK(j.value(std::string_view("_"), json({10, 100})) == json({10, 100}));
+
+                    CHECK(j_const.value(std::string_view("_"), 2) == 2);
+                    CHECK(j_const.value(std::string_view("_"), 2u) == 2u);
+                    CHECK(j_const.value(std::string_view("_"), false) == false);
+                    CHECK(j_const.value(std::string_view("_"), "bar") == "bar");
+                    CHECK(j_const.value(std::string_view("_"), 12.34) == Approx(12.34));
+                    CHECK(j_const.value(std::string_view("_"), json({{"foo", "bar"}})) == json({{"foo", "bar"}}));
+                    CHECK(j_const.value(std::string_view("_"), json({10, 100})) == json({10, 100}));
+#endif
                 }
 
                 SECTION("access on non-object type")
@@ -187,6 +293,11 @@ TEST_CASE("element access 2")
                         const json j_nonobject_const(json::value_t::null);
                         CHECK_THROWS_WITH_AS(j_nonobject.value("foo", 1), "[json.exception.type_error.306] cannot use value() with null", json::type_error&);
                         CHECK_THROWS_WITH_AS(j_nonobject_const.value("foo", 1), "[json.exception.type_error.306] cannot use value() with null", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                        CHECK_THROWS_WITH_AS(j_nonobject.value(std::string_view("foo"), 1), "[json.exception.type_error.306] cannot use value() with null", json::type_error&);
+                        CHECK_THROWS_WITH_AS(j_nonobject_const.value(std::string_view("foo"), 1), "[json.exception.type_error.306] cannot use value() with null", json::type_error&);
+#endif
                     }
 
                     SECTION("boolean")
@@ -195,6 +306,11 @@ TEST_CASE("element access 2")
                         const json j_nonobject_const(json::value_t::boolean);
                         CHECK_THROWS_WITH_AS(j_nonobject.value("foo", 1), "[json.exception.type_error.306] cannot use value() with boolean", json::type_error&);
                         CHECK_THROWS_WITH_AS(j_nonobject_const.value("foo", 1), "[json.exception.type_error.306] cannot use value() with boolean", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                        CHECK_THROWS_WITH_AS(j_nonobject.value(std::string_view("foo"), 1), "[json.exception.type_error.306] cannot use value() with boolean", json::type_error&);
+                        CHECK_THROWS_WITH_AS(j_nonobject_const.value(std::string_view("foo"), 1), "[json.exception.type_error.306] cannot use value() with boolean", json::type_error&);
+#endif
                     }
 
                     SECTION("string")
@@ -203,6 +319,11 @@ TEST_CASE("element access 2")
                         const json j_nonobject_const(json::value_t::string);
                         CHECK_THROWS_WITH_AS(j_nonobject.value("foo", 1), "[json.exception.type_error.306] cannot use value() with string", json::type_error&);
                         CHECK_THROWS_WITH_AS(j_nonobject_const.value("foo", 1), "[json.exception.type_error.306] cannot use value() with string", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                        CHECK_THROWS_WITH_AS(j_nonobject.value(std::string_view("foo"), 1), "[json.exception.type_error.306] cannot use value() with string", json::type_error&);
+                        CHECK_THROWS_WITH_AS(j_nonobject_const.value(std::string_view("foo"), 1), "[json.exception.type_error.306] cannot use value() with string", json::type_error&);
+#endif
                     }
 
                     SECTION("array")
@@ -211,6 +332,11 @@ TEST_CASE("element access 2")
                         const json j_nonobject_const(json::value_t::array);
                         CHECK_THROWS_WITH_AS(j_nonobject.value("foo", 1), "[json.exception.type_error.306] cannot use value() with array", json::type_error&);
                         CHECK_THROWS_WITH_AS(j_nonobject_const.value("foo", 1), "[json.exception.type_error.306] cannot use value() with array", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                        CHECK_THROWS_WITH_AS(j_nonobject.value(std::string_view("foo"), 1), "[json.exception.type_error.306] cannot use value() with array", json::type_error&);
+                        CHECK_THROWS_WITH_AS(j_nonobject_const.value(std::string_view("foo"), 1), "[json.exception.type_error.306] cannot use value() with array", json::type_error&);
+#endif
                     }
 
                     SECTION("number (integer)")
@@ -219,6 +345,11 @@ TEST_CASE("element access 2")
                         const json j_nonobject_const(json::value_t::number_integer);
                         CHECK_THROWS_WITH_AS(j_nonobject.value("foo", 1), "[json.exception.type_error.306] cannot use value() with number", json::type_error&);
                         CHECK_THROWS_WITH_AS(j_nonobject_const.value("foo", 1), "[json.exception.type_error.306] cannot use value() with number", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                        CHECK_THROWS_WITH_AS(j_nonobject.value(std::string_view("foo"), 1), "[json.exception.type_error.306] cannot use value() with number", json::type_error&);
+                        CHECK_THROWS_WITH_AS(j_nonobject_const.value(std::string_view("foo"), 1), "[json.exception.type_error.306] cannot use value() with number", json::type_error&);
+#endif
                     }
 
                     SECTION("number (unsigned)")
@@ -227,6 +358,11 @@ TEST_CASE("element access 2")
                         const json j_nonobject_const(json::value_t::number_unsigned);
                         CHECK_THROWS_WITH_AS(j_nonobject.value("foo", 1), "[json.exception.type_error.306] cannot use value() with number", json::type_error&);
                         CHECK_THROWS_WITH_AS(j_nonobject_const.value("foo", 1), "[json.exception.type_error.306] cannot use value() with number", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                        CHECK_THROWS_WITH_AS(j_nonobject.value(std::string_view("foo"), 1), "[json.exception.type_error.306] cannot use value() with number", json::type_error&);
+                        CHECK_THROWS_WITH_AS(j_nonobject_const.value(std::string_view("foo"), 1), "[json.exception.type_error.306] cannot use value() with number", json::type_error&);
+#endif
                     }
 
                     SECTION("number (floating-point)")
@@ -235,6 +371,11 @@ TEST_CASE("element access 2")
                         const json j_nonobject_const(json::value_t::number_float);
                         CHECK_THROWS_WITH_AS(j_nonobject.value("foo", 1), "[json.exception.type_error.306] cannot use value() with number", json::type_error&);
                         CHECK_THROWS_WITH_AS(j_nonobject_const.value("foo", 1), "[json.exception.type_error.306] cannot use value() with number", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                        CHECK_THROWS_WITH_AS(j_nonobject.value(std::string_view("foo"), 1), "[json.exception.type_error.306] cannot use value() with number", json::type_error&);
+                        CHECK_THROWS_WITH_AS(j_nonobject_const.value(std::string_view("foo"), 1), "[json.exception.type_error.306] cannot use value() with number", json::type_error&);
+#endif
                     }
                 }
             }
@@ -330,6 +471,31 @@ TEST_CASE("element access 2")
             }
         }
 
+        SECTION("non-const operator[]")
+        {
+            {
+                json j_null;
+                CHECK(j_null.is_null());
+                j_null["key"] = 1;
+                CHECK(j_null.is_object());
+                CHECK(j_null.size() == 1);
+                j_null["key"] = 2;
+                CHECK(j_null.size() == 1);
+            }
+#ifdef JSON_HAS_CPP_17
+            {
+                std::string_view key = "key";
+                json j_null;
+                CHECK(j_null.is_null());
+                j_null[key] = 1;
+                CHECK(j_null.is_object());
+                CHECK(j_null.size() == 1);
+                j_null[key] = 2;
+                CHECK(j_null.size() == 1);
+            }
+#endif
+        }
+
         SECTION("front and back")
         {
             // "array" is the smallest key
@@ -390,6 +556,56 @@ TEST_CASE("element access 2")
                 CHECK(j_const[json::object_t::key_type("array")] == j["array"]);
             }
 
+#ifdef JSON_HAS_CPP_17
+            SECTION("access within bounds (string_view)")
+            {
+                CHECK(j["integer"] == json(1));
+                CHECK(j[std::string_view("integer")] == j["integer"]);
+
+                CHECK(j["unsigned"] == json(1u));
+                CHECK(j[std::string_view("unsigned")] == j["unsigned"]);
+
+                CHECK(j["boolean"] == json(true));
+                CHECK(j[std::string_view("boolean")] == j["boolean"]);
+
+                CHECK(j["null"] == json(nullptr));
+                CHECK(j[std::string_view("null")] == j["null"]);
+
+                CHECK(j["string"] == json("hello world"));
+                CHECK(j[std::string_view("string")] == j["string"]);
+
+                CHECK(j["floating"] == json(42.23));
+                CHECK(j[std::string_view("floating")] == j["floating"]);
+
+                CHECK(j["object"] == json::object());
+                CHECK(j[std::string_view("object")] == j["object"]);
+
+                CHECK(j["array"] == json({1, 2, 3}));
+                CHECK(j[std::string_view("array")] == j["array"]);
+
+                CHECK(j_const["integer"] == json(1));
+                CHECK(j_const[std::string_view("integer")] == j["integer"]);
+
+                CHECK(j_const["boolean"] == json(true));
+                CHECK(j_const[std::string_view("boolean")] == j["boolean"]);
+
+                CHECK(j_const["null"] == json(nullptr));
+                CHECK(j_const[std::string_view("null")] == j["null"]);
+
+                CHECK(j_const["string"] == json("hello world"));
+                CHECK(j_const[std::string_view("string")] == j["string"]);
+
+                CHECK(j_const["floating"] == json(42.23));
+                CHECK(j_const[std::string_view("floating")] == j["floating"]);
+
+                CHECK(j_const["object"] == json::object());
+                CHECK(j_const[std::string_view("object")] == j["object"]);
+
+                CHECK(j_const["array"] == json({1, 2, 3}));
+                CHECK(j_const[std::string_view("array")] == j["array"]);
+            }
+#endif
+
             SECTION("access on non-object type")
             {
                 SECTION("null")
@@ -397,10 +613,16 @@ TEST_CASE("element access 2")
                     json j_nonobject(json::value_t::null);
                     json j_nonobject2(json::value_t::null);
                     const json j_const_nonobject(j_nonobject);
+
                     CHECK_NOTHROW(j_nonobject["foo"]);
                     CHECK_NOTHROW(j_nonobject2[json::object_t::key_type("foo")]);
                     CHECK_THROWS_WITH_AS(j_const_nonobject["foo"], "[json.exception.type_error.305] cannot use operator[] with a string argument with null", json::type_error&);
                     CHECK_THROWS_WITH_AS(j_const_nonobject[json::object_t::key_type("foo")], "[json.exception.type_error.305] cannot use operator[] with a string argument with null", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_NOTHROW(j_nonobject2[std::string_view("foo")]);
+                    CHECK_THROWS_WITH_AS(j_const_nonobject[std::string_view("foo")], "[json.exception.type_error.305] cannot use operator[] with a string argument with null", json::type_error&);
+#endif
                 }
 
                 SECTION("boolean")
@@ -415,6 +637,11 @@ TEST_CASE("element access 2")
                                          "[json.exception.type_error.305] cannot use operator[] with a string argument with boolean", json::type_error&);
                     CHECK_THROWS_WITH_AS(j_const_nonobject[json::object_t::key_type("foo")],
                                          "[json.exception.type_error.305] cannot use operator[] with a string argument with boolean", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject[std::string_view("foo")], "[json.exception.type_error.305] cannot use operator[] with a string argument with boolean", json::type_error&);
+                    CHECK_THROWS_WITH_AS(j_const_nonobject[std::string_view("foo")], "[json.exception.type_error.305] cannot use operator[] with a string argument with boolean", json::type_error&);
+#endif
                 }
 
                 SECTION("string")
@@ -429,6 +656,11 @@ TEST_CASE("element access 2")
                                          "[json.exception.type_error.305] cannot use operator[] with a string argument with string", json::type_error&);
                     CHECK_THROWS_WITH_AS(j_const_nonobject[json::object_t::key_type("foo")],
                                          "[json.exception.type_error.305] cannot use operator[] with a string argument with string", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject[std::string_view("foo")], "[json.exception.type_error.305] cannot use operator[] with a string argument with string", json::type_error&);
+                    CHECK_THROWS_WITH_AS(j_const_nonobject[std::string_view("foo")], "[json.exception.type_error.305] cannot use operator[] with a string argument with string", json::type_error&);
+#endif
                 }
 
                 SECTION("array")
@@ -442,6 +674,11 @@ TEST_CASE("element access 2")
                                          "[json.exception.type_error.305] cannot use operator[] with a string argument with array", json::type_error&);
                     CHECK_THROWS_WITH_AS(j_const_nonobject[json::object_t::key_type("foo")],
                                          "[json.exception.type_error.305] cannot use operator[] with a string argument with array", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject[std::string_view("foo")], "[json.exception.type_error.305] cannot use operator[] with a string argument with array", json::type_error&);
+                    CHECK_THROWS_WITH_AS(j_const_nonobject[std::string_view("foo")], "[json.exception.type_error.305] cannot use operator[] with a string argument with array", json::type_error&);
+#endif
                 }
 
                 SECTION("number (integer)")
@@ -456,6 +693,11 @@ TEST_CASE("element access 2")
                                          "[json.exception.type_error.305] cannot use operator[] with a string argument with number", json::type_error&);
                     CHECK_THROWS_WITH_AS(j_const_nonobject[json::object_t::key_type("foo")],
                                          "[json.exception.type_error.305] cannot use operator[] with a string argument with number", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject[std::string_view("foo")], "[json.exception.type_error.305] cannot use operator[] with a string argument with number", json::type_error&);
+                    CHECK_THROWS_WITH_AS(j_const_nonobject[std::string_view("foo")], "[json.exception.type_error.305] cannot use operator[] with a string argument with number", json::type_error&);
+#endif
                 }
 
                 SECTION("number (unsigned)")
@@ -470,6 +712,11 @@ TEST_CASE("element access 2")
                                          "[json.exception.type_error.305] cannot use operator[] with a string argument with number", json::type_error&);
                     CHECK_THROWS_WITH_AS(j_const_nonobject[json::object_t::key_type("foo")],
                                          "[json.exception.type_error.305] cannot use operator[] with a string argument with number", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject[std::string_view("foo")], "[json.exception.type_error.305] cannot use operator[] with a string argument with number", json::type_error&);
+                    CHECK_THROWS_WITH_AS(j_const_nonobject[std::string_view("foo")], "[json.exception.type_error.305] cannot use operator[] with a string argument with number", json::type_error&);
+#endif
                 }
 
                 SECTION("number (floating-point)")
@@ -484,6 +731,11 @@ TEST_CASE("element access 2")
                                          "[json.exception.type_error.305] cannot use operator[] with a string argument with number", json::type_error&);
                     CHECK_THROWS_WITH_AS(j_const_nonobject[json::object_t::key_type("foo")],
                                          "[json.exception.type_error.305] cannot use operator[] with a string argument with number", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject[std::string_view("foo")], "[json.exception.type_error.305] cannot use operator[] with a string argument with number", json::type_error&);
+                    CHECK_THROWS_WITH_AS(j_const_nonobject[std::string_view("foo")], "[json.exception.type_error.305] cannot use operator[] with a string argument with number", json::type_error&);
+#endif
                 }
             }
         }
@@ -533,6 +785,51 @@ TEST_CASE("element access 2")
                 CHECK(j.erase("array") == 0);
             }
 
+#ifdef JSON_HAS_CPP_17
+            SECTION("remove element by key (string_view)")
+            {
+                CHECK(j.find(std::string_view("integer")) != j.end());
+                CHECK(j.erase(std::string_view("integer")) == 1);
+                CHECK(j.find(std::string_view("integer")) == j.end());
+                CHECK(j.erase(std::string_view("integer")) == 0);
+
+                CHECK(j.find(std::string_view("unsigned")) != j.end());
+                CHECK(j.erase(std::string_view("unsigned")) == 1);
+                CHECK(j.find(std::string_view("unsigned")) == j.end());
+                CHECK(j.erase(std::string_view("unsigned")) == 0);
+
+                CHECK(j.find(std::string_view("boolean")) != j.end());
+                CHECK(j.erase(std::string_view("boolean")) == 1);
+                CHECK(j.find(std::string_view("boolean")) == j.end());
+                CHECK(j.erase(std::string_view("boolean")) == 0);
+
+                CHECK(j.find(std::string_view("null")) != j.end());
+                CHECK(j.erase(std::string_view("null")) == 1);
+                CHECK(j.find(std::string_view("null")) == j.end());
+                CHECK(j.erase(std::string_view("null")) == 0);
+
+                CHECK(j.find(std::string_view("string")) != j.end());
+                CHECK(j.erase(std::string_view("string")) == 1);
+                CHECK(j.find(std::string_view("string")) == j.end());
+                CHECK(j.erase(std::string_view("string")) == 0);
+
+                CHECK(j.find(std::string_view("floating")) != j.end());
+                CHECK(j.erase(std::string_view("floating")) == 1);
+                CHECK(j.find(std::string_view("floating")) == j.end());
+                CHECK(j.erase(std::string_view("floating")) == 0);
+
+                CHECK(j.find(std::string_view("object")) != j.end());
+                CHECK(j.erase(std::string_view("object")) == 1);
+                CHECK(j.find(std::string_view("object")) == j.end());
+                CHECK(j.erase(std::string_view("object")) == 0);
+
+                CHECK(j.find(std::string_view("array")) != j.end());
+                CHECK(j.erase(std::string_view("array")) == 1);
+                CHECK(j.find(std::string_view("array")) == j.end());
+                CHECK(j.erase(std::string_view("array")) == 0);
+            }
+#endif
+
             SECTION("remove element by iterator")
             {
                 SECTION("erase(begin())")
@@ -652,36 +949,60 @@ TEST_CASE("element access 2")
                 {
                     json j_nonobject(json::value_t::null);
                     CHECK_THROWS_WITH_AS(j_nonobject.erase("foo"), "[json.exception.type_error.307] cannot use erase() with null", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject.erase(std::string_view("foo")), "[json.exception.type_error.307] cannot use erase() with null", json::type_error&);
+#endif
                 }
 
                 SECTION("boolean")
                 {
                     json j_nonobject(json::value_t::boolean);
                     CHECK_THROWS_WITH_AS(j_nonobject.erase("foo"), "[json.exception.type_error.307] cannot use erase() with boolean", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject.erase(std::string_view("foo")), "[json.exception.type_error.307] cannot use erase() with boolean", json::type_error&);
+#endif
                 }
 
                 SECTION("string")
                 {
                     json j_nonobject(json::value_t::string);
                     CHECK_THROWS_WITH_AS(j_nonobject.erase("foo"), "[json.exception.type_error.307] cannot use erase() with string", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject.erase(std::string_view("foo")), "[json.exception.type_error.307] cannot use erase() with string", json::type_error&);
+#endif
                 }
 
                 SECTION("array")
                 {
                     json j_nonobject(json::value_t::array);
                     CHECK_THROWS_WITH_AS(j_nonobject.erase("foo"), "[json.exception.type_error.307] cannot use erase() with array", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject.erase(std::string_view("foo")), "[json.exception.type_error.307] cannot use erase() with array", json::type_error&);
+#endif
                 }
 
                 SECTION("number (integer)")
                 {
                     json j_nonobject(json::value_t::number_integer);
                     CHECK_THROWS_WITH_AS(j_nonobject.erase("foo"), "[json.exception.type_error.307] cannot use erase() with number", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject.erase(std::string_view("foo")), "[json.exception.type_error.307] cannot use erase() with number", json::type_error&);
+#endif
                 }
 
                 SECTION("number (floating-point)")
                 {
                     json j_nonobject(json::value_t::number_float);
                     CHECK_THROWS_WITH_AS(j_nonobject.erase("foo"), "[json.exception.type_error.307] cannot use erase() with number", json::type_error&);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK_THROWS_WITH_AS(j_nonobject.erase(std::string_view("foo")), "[json.exception.type_error.307] cannot use erase() with number", json::type_error&);
+#endif
                 }
             }
         }
@@ -699,12 +1020,28 @@ TEST_CASE("element access 2")
                     CHECK(j_const.find(key) != j_const.end());
                     CHECK(*j_const.find(key) == j_const.at(key));
                 }
+#ifdef JSON_HAS_CPP_17
+                for (const std::string_view key :
+                        {"integer", "unsigned", "floating", "null", "string", "boolean", "object", "array"
+                        })
+                {
+                    CHECK(j.find(key) != j.end());
+                    CHECK(*j.find(key) == j.at(key));
+                    CHECK(j_const.find(key) != j_const.end());
+                    CHECK(*j_const.find(key) == j_const.at(key));
+                }
+#endif
             }
 
             SECTION("nonexisting element")
             {
                 CHECK(j.find("foo") == j.end());
                 CHECK(j_const.find("foo") == j_const.end());
+
+#ifdef JSON_HAS_CPP_17
+                CHECK(j.find(std::string_view("foo")) == j.end());
+                CHECK(j_const.find(std::string_view("foo")) == j_const.end());
+#endif
             }
 
             SECTION("all types")
@@ -713,64 +1050,112 @@ TEST_CASE("element access 2")
                 {
                     json j_nonarray(json::value_t::null);
                     const json j_nonarray_const(j_nonarray);
+
                     CHECK(j_nonarray.find("foo") == j_nonarray.end());
                     CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonarray.find(std::string_view("foo")) == j_nonarray.end());
+                    CHECK(j_nonarray_const.find(std::string_view("foo")) == j_nonarray_const.end());
+#endif
                 }
 
                 SECTION("string")
                 {
                     json j_nonarray(json::value_t::string);
                     const json j_nonarray_const(j_nonarray);
+
                     CHECK(j_nonarray.find("foo") == j_nonarray.end());
                     CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonarray.find(std::string_view("foo")) == j_nonarray.end());
+                    CHECK(j_nonarray_const.find(std::string_view("foo")) == j_nonarray_const.end());
+#endif
                 }
 
                 SECTION("object")
                 {
                     json j_nonarray(json::value_t::object);
                     const json j_nonarray_const(j_nonarray);
+
                     CHECK(j_nonarray.find("foo") == j_nonarray.end());
                     CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonarray.find(std::string_view("foo")) == j_nonarray.end());
+                    CHECK(j_nonarray_const.find(std::string_view("foo")) == j_nonarray_const.end());
+#endif
                 }
 
                 SECTION("array")
                 {
                     json j_nonarray(json::value_t::array);
                     const json j_nonarray_const(j_nonarray);
+
                     CHECK(j_nonarray.find("foo") == j_nonarray.end());
                     CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonarray.find(std::string_view("foo")) == j_nonarray.end());
+                    CHECK(j_nonarray_const.find(std::string_view("foo")) == j_nonarray_const.end());
+#endif
                 }
 
                 SECTION("boolean")
                 {
                     json j_nonarray(json::value_t::boolean);
                     const json j_nonarray_const(j_nonarray);
+
                     CHECK(j_nonarray.find("foo") == j_nonarray.end());
                     CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonarray.find(std::string_view("foo")) == j_nonarray.end());
+                    CHECK(j_nonarray_const.find(std::string_view("foo")) == j_nonarray_const.end());
+#endif
                 }
 
                 SECTION("number (integer)")
                 {
                     json j_nonarray(json::value_t::number_integer);
                     const json j_nonarray_const(j_nonarray);
+
                     CHECK(j_nonarray.find("foo") == j_nonarray.end());
                     CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonarray.find(std::string_view("foo")) == j_nonarray.end());
+                    CHECK(j_nonarray_const.find(std::string_view("foo")) == j_nonarray_const.end());
+#endif
                 }
 
                 SECTION("number (unsigned)")
                 {
                     json j_nonarray(json::value_t::number_unsigned);
                     const json j_nonarray_const(j_nonarray);
+
                     CHECK(j_nonarray.find("foo") == j_nonarray.end());
                     CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonarray.find(std::string_view("foo")) == j_nonarray.end());
+                    CHECK(j_nonarray_const.find(std::string_view("foo")) == j_nonarray_const.end());
+#endif
                 }
 
                 SECTION("number (floating-point)")
                 {
                     json j_nonarray(json::value_t::number_float);
                     const json j_nonarray_const(j_nonarray);
+
                     CHECK(j_nonarray.find("foo") == j_nonarray.end());
                     CHECK(j_nonarray_const.find("foo") == j_nonarray_const.end());
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonarray.find(std::string_view("foo")) == j_nonarray.end());
+                    CHECK(j_nonarray_const.find(std::string_view("foo")) == j_nonarray_const.end());
+#endif
                 }
             }
         }
@@ -786,12 +1171,26 @@ TEST_CASE("element access 2")
                     CHECK(j.count(key) == 1);
                     CHECK(j_const.count(key) == 1);
                 }
+#ifdef JSON_HAS_CPP_17
+                for (const std::string_view key :
+                        {"integer", "unsigned", "floating", "null", "string", "boolean", "object", "array"
+                        })
+                {
+                    CHECK(j.count(key) == 1);
+                    CHECK(j_const.count(key) == 1);
+                }
+#endif
             }
 
             SECTION("nonexisting element")
             {
                 CHECK(j.count("foo") == 0);
                 CHECK(j_const.count("foo") == 0);
+
+#ifdef JSON_HAS_CPP_17
+                CHECK(j.count(std::string_view("foo")) == 0);
+                CHECK(j_const.count(std::string_view("foo")) == 0);
+#endif
             }
 
             SECTION("all types")
@@ -800,64 +1199,112 @@ TEST_CASE("element access 2")
                 {
                     json j_nonobject(json::value_t::null);
                     const json j_nonobject_const(json::value_t::null);
+
                     CHECK(j_nonobject.count("foo") == 0);
                     CHECK(j_nonobject_const.count("foo") == 0);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j.count(std::string_view("foo")) == 0);
+                    CHECK(j_const.count(std::string_view("foo")) == 0);
+#endif
                 }
 
                 SECTION("string")
                 {
                     json j_nonobject(json::value_t::string);
                     const json j_nonobject_const(json::value_t::string);
+
                     CHECK(j_nonobject.count("foo") == 0);
                     CHECK(j_nonobject_const.count("foo") == 0);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j.count(std::string_view("foo")) == 0);
+                    CHECK(j_const.count(std::string_view("foo")) == 0);
+#endif
                 }
 
                 SECTION("object")
                 {
                     json j_nonobject(json::value_t::object);
                     const json j_nonobject_const(json::value_t::object);
+
                     CHECK(j_nonobject.count("foo") == 0);
                     CHECK(j_nonobject_const.count("foo") == 0);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j.count(std::string_view("foo")) == 0);
+                    CHECK(j_const.count(std::string_view("foo")) == 0);
+#endif
                 }
 
                 SECTION("array")
                 {
                     json j_nonobject(json::value_t::array);
                     const json j_nonobject_const(json::value_t::array);
+
                     CHECK(j_nonobject.count("foo") == 0);
                     CHECK(j_nonobject_const.count("foo") == 0);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j.count(std::string_view("foo")) == 0);
+                    CHECK(j_const.count(std::string_view("foo")) == 0);
+#endif
                 }
 
                 SECTION("boolean")
                 {
                     json j_nonobject(json::value_t::boolean);
                     const json j_nonobject_const(json::value_t::boolean);
+
                     CHECK(j_nonobject.count("foo") == 0);
                     CHECK(j_nonobject_const.count("foo") == 0);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j.count(std::string_view("foo")) == 0);
+                    CHECK(j_const.count(std::string_view("foo")) == 0);
+#endif
                 }
 
                 SECTION("number (integer)")
                 {
                     json j_nonobject(json::value_t::number_integer);
                     const json j_nonobject_const(json::value_t::number_integer);
+
                     CHECK(j_nonobject.count("foo") == 0);
                     CHECK(j_nonobject_const.count("foo") == 0);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j.count(std::string_view("foo")) == 0);
+                    CHECK(j_const.count(std::string_view("foo")) == 0);
+#endif
                 }
 
                 SECTION("number (unsigned)")
                 {
                     json j_nonobject(json::value_t::number_unsigned);
                     const json j_nonobject_const(json::value_t::number_unsigned);
+
                     CHECK(j_nonobject.count("foo") == 0);
                     CHECK(j_nonobject_const.count("foo") == 0);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j.count(std::string_view("foo")) == 0);
+                    CHECK(j_const.count(std::string_view("foo")) == 0);
+#endif
                 }
 
                 SECTION("number (floating-point)")
                 {
                     json j_nonobject(json::value_t::number_float);
                     const json j_nonobject_const(json::value_t::number_float);
+
                     CHECK(j_nonobject.count("foo") == 0);
                     CHECK(j_nonobject_const.count("foo") == 0);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j.count(std::string_view("foo")) == 0);
+                    CHECK(j_const.count(std::string_view("foo")) == 0);
+#endif
                 }
             }
         }
@@ -873,12 +1320,27 @@ TEST_CASE("element access 2")
                     CHECK(j.contains(key) == true);
                     CHECK(j_const.contains(key) == true);
                 }
+
+#ifdef JSON_HAS_CPP_17
+                for (const std::string_view key :
+                        {"integer", "unsigned", "floating", "null", "string", "boolean", "object", "array"
+                        })
+                {
+                    CHECK(j.contains(key) == true);
+                    CHECK(j_const.contains(key) == true);
+                }
+#endif
             }
 
             SECTION("nonexisting element")
             {
                 CHECK(j.contains("foo") == false);
                 CHECK(j_const.contains("foo") == false);
+
+#ifdef JSON_HAS_CPP_17
+                CHECK(j.contains(std::string_view("foo")) == false);
+                CHECK(j_const.contains(std::string_view("foo")) == false);
+#endif
             }
 
             SECTION("all types")
@@ -887,56 +1349,98 @@ TEST_CASE("element access 2")
                 {
                     json j_nonobject(json::value_t::null);
                     const json j_nonobject_const(json::value_t::null);
+
                     CHECK(j_nonobject.contains("foo") == false);
                     CHECK(j_nonobject_const.contains("foo") == false);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonobject.contains(std::string_view("foo")) == false);
+                    CHECK(j_nonobject_const.contains(std::string_view("foo")) == false);
+#endif
                 }
 
                 SECTION("string")
                 {
                     json j_nonobject(json::value_t::string);
                     const json j_nonobject_const(json::value_t::string);
+
                     CHECK(j_nonobject.contains("foo") == false);
                     CHECK(j_nonobject_const.contains("foo") == false);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonobject.contains(std::string_view("foo")) == false);
+                    CHECK(j_nonobject_const.contains(std::string_view("foo")) == false);
+#endif
                 }
 
                 SECTION("object")
                 {
                     json j_nonobject(json::value_t::object);
                     const json j_nonobject_const(json::value_t::object);
+
                     CHECK(j_nonobject.contains("foo") == false);
                     CHECK(j_nonobject_const.contains("foo") == false);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonobject.contains(std::string_view("foo")) == false);
+                    CHECK(j_nonobject_const.contains(std::string_view("foo")) == false);
+#endif
                 }
 
                 SECTION("array")
                 {
                     json j_nonobject(json::value_t::array);
                     const json j_nonobject_const(json::value_t::array);
+
                     CHECK(j_nonobject.contains("foo") == false);
                     CHECK(j_nonobject_const.contains("foo") == false);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonobject.contains(std::string_view("foo")) == false);
+                    CHECK(j_nonobject_const.contains(std::string_view("foo")) == false);
+#endif
                 }
 
                 SECTION("boolean")
                 {
                     json j_nonobject(json::value_t::boolean);
                     const json j_nonobject_const(json::value_t::boolean);
+
                     CHECK(j_nonobject.contains("foo") == false);
                     CHECK(j_nonobject_const.contains("foo") == false);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonobject.contains(std::string_view("foo")) == false);
+                    CHECK(j_nonobject_const.contains(std::string_view("foo")) == false);
+#endif
                 }
 
                 SECTION("number (integer)")
                 {
                     json j_nonobject(json::value_t::number_integer);
                     const json j_nonobject_const(json::value_t::number_integer);
+
                     CHECK(j_nonobject.contains("foo") == false);
                     CHECK(j_nonobject_const.contains("foo") == false);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonobject.contains(std::string_view("foo")) == false);
+                    CHECK(j_nonobject_const.contains(std::string_view("foo")) == false);
+#endif
                 }
 
                 SECTION("number (unsigned)")
                 {
                     json j_nonobject(json::value_t::number_unsigned);
                     const json j_nonobject_const(json::value_t::number_unsigned);
+
                     CHECK(j_nonobject.contains("foo") == false);
                     CHECK(j_nonobject_const.contains("foo") == false);
+
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonobject.contains(std::string_view("foo")) == false);
+                    CHECK(j_nonobject_const.contains(std::string_view("foo")) == false);
+#endif
                 }
 
                 SECTION("number (floating-point)")
@@ -945,6 +1449,10 @@ TEST_CASE("element access 2")
                     const json j_nonobject_const(json::value_t::number_float);
                     CHECK(j_nonobject.contains("foo") == false);
                     CHECK(j_nonobject_const.contains("foo") == false);
+#ifdef JSON_HAS_CPP_17
+                    CHECK(j_nonobject.contains(std::string_view("foo")) == false);
+                    CHECK(j_nonobject_const.contains(std::string_view("foo")) == false);
+#endif
                 }
             }
         }