diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 94a493992e593..2f6686f81965b 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -411,7 +411,7 @@ struct HandlerInner {
     /// would be unnecessary repetition.
     taught_diagnostics: FxHashSet<DiagnosticId>,
 
-    /// Used to suggest rustc --explain <error code>
+    /// Used to suggest rustc --explain `<error code>`
     emitted_diagnostic_codes: FxIndexSet<DiagnosticId>,
 
     /// This set contains a hash of every diagnostic that has been emitted by
diff --git a/src/librustdoc/lint.rs b/src/librustdoc/lint.rs
index e76c19a61c541..3aad97bc296fb 100644
--- a/src/librustdoc/lint.rs
+++ b/src/librustdoc/lint.rs
@@ -148,7 +148,7 @@ declare_rustdoc_lint! {
     ///
     /// [rustdoc book]: ../../../rustdoc/lints.html#invalid_html_tags
     INVALID_HTML_TAGS,
-    Allow,
+    Warn,
     "detects invalid HTML tags in doc comments"
 }
 
diff --git a/src/librustdoc/passes/html_tags.rs b/src/librustdoc/passes/html_tags.rs
index 694b03161d929..67fc71665ccf7 100644
--- a/src/librustdoc/passes/html_tags.rs
+++ b/src/librustdoc/passes/html_tags.rs
@@ -22,10 +22,8 @@ struct InvalidHtmlTagsLinter<'a, 'tcx> {
 }
 
 pub(crate) fn check_invalid_html_tags(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
-    if cx.tcx.sess.is_nightly_build() {
-        let mut coll = InvalidHtmlTagsLinter { cx };
-        coll.visit_crate(&krate);
-    }
+    let mut coll = InvalidHtmlTagsLinter { cx };
+    coll.visit_crate(&krate);
     krate
 }
 
diff --git a/src/test/rustdoc-ui/intra-doc/malformed-generics.rs b/src/test/rustdoc-ui/intra-doc/malformed-generics.rs
index 15e02925ed90d..161625ed28c29 100644
--- a/src/test/rustdoc-ui/intra-doc/malformed-generics.rs
+++ b/src/test/rustdoc-ui/intra-doc/malformed-generics.rs
@@ -3,17 +3,26 @@
 //! [Vec<] //~ ERROR
 //! [Vec<Box<T] //~ ERROR
 //! [Vec<Box<T>] //~ ERROR
+//~^ WARN
 //! [Vec<Box<T>>>] //~ ERROR
+//~^ WARN
 //! [Vec<T>>>] //~ ERROR
+//~^ WARN
 //! [<Vec] //~ ERROR
 //! [Vec::<] //~ ERROR
 //! [<T>] //~ ERROR
+//~^ WARN
 //! [<invalid syntax>] //~ ERROR
+//~^ WARN
 //! [Vec:<T>:new()] //~ ERROR
+//~^ WARN
 //! [Vec<<T>>] //~ ERROR
+//~^ WARN
 //! [Vec<>] //~ ERROR
 //! [Vec<<>>] //~ ERROR
 
 // FIXME(#74563) support UFCS
 //! [<Vec as IntoIterator>::into_iter] //~ ERROR
+//~^ WARN
 //! [<Vec<T> as IntoIterator>::iter] //~ ERROR
+//~^ WARN
diff --git a/src/test/rustdoc-ui/intra-doc/malformed-generics.stderr b/src/test/rustdoc-ui/intra-doc/malformed-generics.stderr
index 5bc0f84e24d13..08349fef88d38 100644
--- a/src/test/rustdoc-ui/intra-doc/malformed-generics.stderr
+++ b/src/test/rustdoc-ui/intra-doc/malformed-generics.stderr
@@ -23,67 +23,67 @@ LL | //! [Vec<Box<T>]
    |      ^^^^^^^^^^ unbalanced angle brackets
 
 error: unresolved link to `Vec<Box<T>>>`
-  --> $DIR/malformed-generics.rs:6:6
+  --> $DIR/malformed-generics.rs:7:6
    |
 LL | //! [Vec<Box<T>>>]
    |      ^^^^^^^^^^^^ unbalanced angle brackets
 
 error: unresolved link to `Vec<T>>>`
-  --> $DIR/malformed-generics.rs:7:6
+  --> $DIR/malformed-generics.rs:9:6
    |
 LL | //! [Vec<T>>>]
    |      ^^^^^^^^ unbalanced angle brackets
 
 error: unresolved link to `<Vec`
-  --> $DIR/malformed-generics.rs:8:6
+  --> $DIR/malformed-generics.rs:11:6
    |
 LL | //! [<Vec]
    |      ^^^^ unbalanced angle brackets
 
 error: unresolved link to `Vec::<`
-  --> $DIR/malformed-generics.rs:9:6
+  --> $DIR/malformed-generics.rs:12:6
    |
 LL | //! [Vec::<]
    |      ^^^^^^ unbalanced angle brackets
 
 error: unresolved link to `<T>`
-  --> $DIR/malformed-generics.rs:10:6
+  --> $DIR/malformed-generics.rs:13:6
    |
 LL | //! [<T>]
    |      ^^^ missing type for generic parameters
 
 error: unresolved link to `<invalid syntax>`
-  --> $DIR/malformed-generics.rs:11:6
+  --> $DIR/malformed-generics.rs:15:6
    |
 LL | //! [<invalid syntax>]
    |      ^^^^^^^^^^^^^^^^ missing type for generic parameters
 
 error: unresolved link to `Vec:<T>:new`
-  --> $DIR/malformed-generics.rs:12:6
+  --> $DIR/malformed-generics.rs:17:6
    |
 LL | //! [Vec:<T>:new()]
    |      ^^^^^^^^^^^^^ has invalid path separator
 
 error: unresolved link to `Vec<<T>>`
-  --> $DIR/malformed-generics.rs:13:6
+  --> $DIR/malformed-generics.rs:19:6
    |
 LL | //! [Vec<<T>>]
    |      ^^^^^^^^ too many angle brackets
 
 error: unresolved link to `Vec<>`
-  --> $DIR/malformed-generics.rs:14:6
+  --> $DIR/malformed-generics.rs:21:6
    |
 LL | //! [Vec<>]
    |      ^^^^^ empty angle brackets
 
 error: unresolved link to `Vec<<>>`
-  --> $DIR/malformed-generics.rs:15:6
+  --> $DIR/malformed-generics.rs:22:6
    |
 LL | //! [Vec<<>>]
    |      ^^^^^^^ too many angle brackets
 
 error: unresolved link to `<Vec as IntoIterator>::into_iter`
-  --> $DIR/malformed-generics.rs:18:6
+  --> $DIR/malformed-generics.rs:25:6
    |
 LL | //! [<Vec as IntoIterator>::into_iter]
    |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ fully-qualified syntax is unsupported
@@ -91,12 +91,68 @@ LL | //! [<Vec as IntoIterator>::into_iter]
    = note: see https://github.com/rust-lang/rust/issues/74563 for more information
 
 error: unresolved link to `<Vec<T> as IntoIterator>::iter`
-  --> $DIR/malformed-generics.rs:19:6
+  --> $DIR/malformed-generics.rs:27:6
    |
 LL | //! [<Vec<T> as IntoIterator>::iter]
    |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ fully-qualified syntax is unsupported
    |
    = note: see https://github.com/rust-lang/rust/issues/74563 for more information
 
-error: aborting due to 15 previous errors
+warning: unclosed HTML tag `T`
+  --> $DIR/malformed-generics.rs:5:13
+   |
+LL | //! [Vec<Box<T>]
+   |             ^^^
+   |
+   = note: `#[warn(rustdoc::invalid_html_tags)]` on by default
+
+warning: unclosed HTML tag `T`
+  --> $DIR/malformed-generics.rs:7:13
+   |
+LL | //! [Vec<Box<T>>>]
+   |             ^^^
+
+warning: unclosed HTML tag `T`
+  --> $DIR/malformed-generics.rs:9:9
+   |
+LL | //! [Vec<T>>>]
+   |         ^^^
+
+warning: unclosed HTML tag `T`
+  --> $DIR/malformed-generics.rs:13:6
+   |
+LL | //! [<T>]
+   |      ^^^
+
+warning: unclosed HTML tag `invalid`
+  --> $DIR/malformed-generics.rs:15:6
+   |
+LL | //! [<invalid syntax>]
+   |      ^^^^^^^^
+
+warning: unclosed HTML tag `T`
+  --> $DIR/malformed-generics.rs:17:10
+   |
+LL | //! [Vec:<T>:new()]
+   |          ^^^
+
+warning: unclosed HTML tag `T`
+  --> $DIR/malformed-generics.rs:19:10
+   |
+LL | //! [Vec<<T>>]
+   |          ^^^
+
+warning: unclosed HTML tag `Vec`
+  --> $DIR/malformed-generics.rs:25:6
+   |
+LL | //! [<Vec as IntoIterator>::into_iter]
+   |      ^^^^
+
+warning: unclosed HTML tag `T`
+  --> $DIR/malformed-generics.rs:27:10
+   |
+LL | //! [<Vec<T> as IntoIterator>::iter]
+   |          ^^^
+
+error: aborting due to 15 previous errors; 9 warnings emitted
 
diff --git a/src/test/rustdoc/intra-doc/extern-crate-only-used-in-link.rs b/src/test/rustdoc/intra-doc/extern-crate-only-used-in-link.rs
index 5d8dcf8bc1d16..ad50887e9221c 100644
--- a/src/test/rustdoc/intra-doc/extern-crate-only-used-in-link.rs
+++ b/src/test/rustdoc/intra-doc/extern-crate-only-used-in-link.rs
@@ -16,4 +16,4 @@
 //! [`empty`]
 
 // @has - '//a[@href="../empty2/index.html"]' 'empty2'
-//! [empty2<x>]
+//! [`empty2<x>`]