diff --git a/pipeline/compressors/__init__.py b/pipeline/compressors/__init__.py
index fb1cd738..fe749500 100644
--- a/pipeline/compressors/__init__.py
+++ b/pipeline/compressors/__init__.py
@@ -1,9 +1,13 @@
+from __future__ import annotations
+
 import base64
 import os
 import posixpath
 import re
 import subprocess
+import warnings
 from itertools import takewhile
+from typing import Iterator, Optional, Sequence
 
 from django.contrib.staticfiles.storage import staticfiles_storage
 from django.utils.encoding import force_str, smart_bytes
@@ -12,8 +16,57 @@
 from pipeline.exceptions import CompressorError
 from pipeline.utils import relpath, set_std_streams_blocking, to_class
 
-URL_DETECTOR = r"""url\((['"]?)\s*(.*?)\1\)"""
-URL_REPLACER = r"""url\(__EMBED__(.+?)(\?\d+)?\)"""
+# Regex matching url(...), url('...'), and url("...") patterns.
+#
+# Replacements will preserve the quotes and any whitespace contained within
+# the pattern, transforming only the filename.
+#
+# Verbose and documented, to ease future maintenance.
+_CSS_URL_REWRITE_PATH_RE_STR = r"""
+    (?P<url_prefix>
+      url\(                 # The opening `url(`.
+      (?P<url_quote>['"]?)  # Optional quote (' or ").
+      \s*
+    )
+    (?P<url_path>.*?)       # The path to capture.
+    (?P<url_suffix>
+      (?P=url_quote)        # The quote found earlier, if any.
+      \s*
+      \)                    # The end `)`, completing `url(...)`.
+    )
+"""
+
+
+# Regex matching `//@ sourceMappingURL=...` and variants.
+#
+# This will capture sourceMappingURL and sourceURL keywords, both
+# `//@` and `//#` variants, and both `//` and `/* ... */` comment types.
+#
+# Verbose and documented, to ease future maintenance.
+_SOURCEMAP_REWRITE_PATH_RE_STR = r"""
+    (?P<sourcemap_prefix>
+      /(?:/|(?P<sourcemap_mlcomment>\*))  # Opening comment (`//#`, `//@`,
+      [#@]\s+                             # `/*@`, `/*#`).
+      source(?:Mapping)?URL=              # The sourcemap indicator.
+      \s*
+    )
+    (?P<sourcemap_path>.*?)               # The path to capture.
+    (?P<sourcemap_suffix>
+      \s*
+      (?(sourcemap_mlcomment)\*/\s*)      # End comment (`*/`)
+    )
+    $                                     # The line should now end.
+"""
+
+
+# Implementation of the above regexes, for CSS and JavaScript.
+CSS_REWRITE_PATH_RE = re.compile(
+    f"{_CSS_URL_REWRITE_PATH_RE_STR}|{_SOURCEMAP_REWRITE_PATH_RE_STR}", re.X | re.M
+)
+JS_REWRITE_PATH_RE = re.compile(_SOURCEMAP_REWRITE_PATH_RE_STR, re.X | re.M)
+
+
+URL_REPLACER = re.compile(r"""url\(__EMBED__(.+?)(\?\d+)?\)""")
 NON_REWRITABLE_URL = re.compile(r"^(#|http:|https:|data:|//)")
 
 DEFAULT_TEMPLATE_FUNC = "template"
@@ -51,9 +104,27 @@ def js_compressor(self):
     def css_compressor(self):
         return to_class(settings.CSS_COMPRESSOR)
 
-    def compress_js(self, paths, templates=None, **kwargs):
+    def compress_js(
+        self,
+        paths: Sequence[str],
+        templates: Optional[Sequence[str]] = None,
+        *,
+        output_filename: Optional[str] = None,
+        **kwargs,
+    ) -> str:
         """Concatenate and compress JS files"""
-        js = self.concatenate(paths)
+        # Note how a semicolon is added between the two files to make sure that
+        # their behavior is not changed. '(expression1)\n(expression2)' calls
+        # `expression1` with `expression2` as an argument! Superfluous
+        # semicolons are valid in JavaScript and will be removed by the
+        # minifier.
+        js = self.concatenate(
+            paths,
+            file_sep=";",
+            output_filename=output_filename,
+            rewrite_path_re=JS_REWRITE_PATH_RE,
+        )
+
         if templates:
             js = js + self.compile_templates(templates)
 
@@ -68,7 +139,13 @@ def compress_js(self, paths, templates=None, **kwargs):
 
     def compress_css(self, paths, output_filename, variant=None, **kwargs):
         """Concatenate and compress CSS files"""
-        css = self.concatenate_and_rewrite(paths, output_filename, variant)
+        css = self.concatenate(
+            paths,
+            file_sep="",
+            rewrite_path_re=CSS_REWRITE_PATH_RE,
+            output_filename=output_filename,
+            variant=variant,
+        )
         compressor = self.css_compressor
         if compressor:
             css = getattr(compressor(verbose=self.verbose), "compress_css")(css)
@@ -131,38 +208,116 @@ def template_name(self, path, base):
 
     def concatenate_and_rewrite(self, paths, output_filename, variant=None):
         """Concatenate together files and rewrite urls"""
-        stylesheets = []
-        for path in paths:
+        warnings.warn(
+            "Compressor.concatenate_and_rewrite() is deprecated. Please "
+            "call concatenate() instead.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
 
-            def reconstruct(match):
-                quote = match.group(1) or ""
-                asset_path = match.group(2)
-                if NON_REWRITABLE_URL.match(asset_path):
-                    return f"url({quote}{asset_path}{quote})"
-                asset_url = self.construct_asset_path(
-                    asset_path, path, output_filename, variant
+        return self.concatenate(
+            paths=paths,
+            file_sep="",
+            rewrite_path_re=CSS_REWRITE_PATH_RE,
+            output_filename=output_filename,
+            variant=variant,
+        )
+
+    def concatenate(
+        self,
+        paths: Sequence[str],
+        *,
+        file_sep: Optional[str] = None,
+        output_filename: Optional[str] = None,
+        rewrite_path_re: Optional[re.Pattern] = None,
+        variant: Optional[str] = None,
+    ) -> str:
+        """Concatenate together a list of files.
+
+        The caller can specify a delimiter between files and any regexes
+        used to normalize relative paths. Path normalization is important for
+        ensuring that local resources or sourcemaps can be updated in time
+        for Django's static media post-processing phase.
+        """
+
+        def _reconstruct(
+            m: re.Match,
+            source_path: str,
+        ) -> str:
+            groups = m.groupdict()
+            asset_path: Optional[str] = None
+            prefix = ""
+            suffix = ""
+
+            for prefix in ("sourcemap", "url"):
+                asset_path = groups.get(f"{prefix}_path")
+
+                if asset_path is not None:
+                    asset_path = asset_path.strip()
+                    prefix, suffix = m.group(f"{prefix}_prefix", f"{prefix}_suffix")
+                    break
+
+            if asset_path is None:
+                # This is empty. Return the whole match as-is.
+                return m.group()
+
+            if asset_path and not NON_REWRITABLE_URL.match(asset_path):
+                asset_path = self.construct_asset_path(
+                    asset_path=asset_path,
+                    source_path=source_path,
+                    output_filename=output_filename,
+                    variant=variant,
                 )
-                return f"url({asset_url})"
 
-            content = self.read_text(path)
-            # content needs to be unicode to avoid explosions with non-ascii chars
-            content = re.sub(URL_DETECTOR, reconstruct, content)
-            stylesheets.append(content)
-        return "\n".join(stylesheets)
+            return f"{prefix}{asset_path}{suffix}"
+
+        def _iter_files() -> Iterator[str]:
+            if not output_filename or not rewrite_path_re:
+                # This is legacy call, which does not support sourcemap-aware
+                # asset rewriting. Pipeline itself won't invoke this outside
+                # of tests, but it maybe important for third-parties who
+                # are specializing these classes.
+                warnings.warn(
+                    "Compressor.concatenate() was called without passing "
+                    "rewrite_path_re_= or output_filename=. If you are "
+                    "specializing Compressor, please update your call "
+                    "to remain compatible with future changes.",
+                    DeprecationWarning,
+                    stacklevel=3,
+                )
 
-    def concatenate(self, paths):
-        """Concatenate together a list of files"""
-        # Note how a semicolon is added between the two files to make sure that
-        # their behavior is not changed. '(expression1)\n(expression2)' calls
-        # `expression1` with `expression2` as an argument! Superfluos semicolons
-        # are valid in JavaScript and will be removed by the minifier.
-        return "\n;".join([self.read_text(path) for path in paths])
+                return (self.read_text(path) for path in paths)
+
+            # Now that we can attempt the modern support for concatenating
+            # files, handling rewriting of relative assets in the process.
+            return (
+                rewrite_path_re.sub(
+                    lambda m: _reconstruct(m, path), self.read_text(path)
+                )
+                for path in paths
+            )
+
+        if file_sep is None:
+            warnings.warn(
+                "Compressor.concatenate() was called without passing "
+                "file_sep=. If you are specializing Compressor, please "
+                "update your call to remain compatible with future changes. "
+                "Defaulting to JavaScript behavior for "
+                "backwards-compatibility.",
+                DeprecationWarning,
+                stacklevel=2,
+            )
+            file_sep = ";"
+
+        return f"\n{file_sep}".join(_iter_files())
 
-    def construct_asset_path(self, asset_path, css_path, output_filename, variant=None):
-        """Return a rewritten asset URL for a stylesheet"""
+    def construct_asset_path(
+        self, asset_path, source_path, output_filename, variant=None
+    ):
+        """Return a rewritten asset URL for a stylesheet or JavaScript file."""
         public_path = self.absolute_path(
             asset_path,
-            os.path.dirname(css_path).replace("\\", "/"),
+            os.path.dirname(source_path).replace("\\", "/"),
         )
         if self.embeddable(public_path, variant):
             return "__EMBED__%s" % public_path
@@ -196,7 +351,7 @@ def datauri(match):
             data = self.encoded_content(path)
             return f'url("data:{mime_type};charset=utf-8;base64,{data}")'
 
-        return re.sub(URL_REPLACER, datauri, css)
+        return URL_REPLACER.sub(datauri, css)
 
     def encoded_content(self, path):
         """Return the base64 encoded contents"""
diff --git a/pipeline/packager.py b/pipeline/packager.py
index f6c4a3ef..20f34197 100644
--- a/pipeline/packager.py
+++ b/pipeline/packager.py
@@ -152,6 +152,7 @@ def pack_javascripts(self, package, **kwargs):
             package,
             self.compressor.compress_js,
             js_compressed,
+            output_filename=package.output_filename,
             templates=package.templates,
             **kwargs,
         )
diff --git a/tests/assets/css/sourcemap.css b/tests/assets/css/sourcemap.css
new file mode 100644
index 00000000..30e87e8b
--- /dev/null
+++ b/tests/assets/css/sourcemap.css
@@ -0,0 +1,24 @@
+div {
+  display: inline;
+}
+
+span {
+  display: block;
+}
+
+
+//#  sourceMappingURL=sourcemap1.css.map
+
+//@ sourceMappingURL=sourcemap2.css.map  
+
+/*#  sourceMappingURL=sourcemap3.css.map */
+
+/*@ sourceMappingURL=sourcemap4.css.map  */
+
+//#  sourceURL=sourcemap5.css.map
+
+//@ sourceURL=sourcemap6.css.map  
+
+/*#  sourceURL=sourcemap7.css.map */
+
+/*@ sourceURL=sourcemap8.css.map  */
diff --git a/tests/assets/js/sourcemap.js b/tests/assets/js/sourcemap.js
new file mode 100644
index 00000000..4d609994
--- /dev/null
+++ b/tests/assets/js/sourcemap.js
@@ -0,0 +1,18 @@
+const abc = 123;
+
+
+//#  sourceMappingURL=sourcemap1.js.map
+
+//@ sourceMappingURL=sourcemap2.js.map  
+
+/*#  sourceMappingURL=sourcemap3.js.map */
+
+/*@ sourceMappingURL=sourcemap4.js.map  */
+
+//#  sourceURL=sourcemap5.js.map
+
+//@ sourceURL=sourcemap6.js.map  
+
+/*#  sourceURL=sourcemap7.js.map */
+
+/*@ sourceURL=sourcemap8.js.map  */
diff --git a/tests/tests/test_compressor.py b/tests/tests/test_compressor.py
index fc5ce538..0a7c7ccd 100644
--- a/tests/tests/test_compressor.py
+++ b/tests/tests/test_compressor.py
@@ -14,7 +14,13 @@
 from django.test.client import RequestFactory
 
 from pipeline.collector import default_collector
-from pipeline.compressors import TEMPLATE_FUNC, Compressor, SubProcessCompressor
+from pipeline.compressors import (
+    CSS_REWRITE_PATH_RE,
+    JS_REWRITE_PATH_RE,
+    TEMPLATE_FUNC,
+    Compressor,
+    SubProcessCompressor,
+)
 from pipeline.compressors.yuglify import YuglifyCompressor
 from tests.utils import _, pipeline_settings
 
@@ -160,22 +166,25 @@ def test_construct_asset_path(self):
         )
         self.assertEqual(asset_path, "/images/sprite.png")
 
-    def test_url_rewrite(self):
-        output = self.compressor.concatenate_and_rewrite(
+    def test_concatenate_with_url_rewrite(self) -> None:
+        output = self.compressor.concatenate(
             [
                 _("pipeline/css/urls.css"),
             ],
-            "css/screen.css",
+            file_sep="",
+            output_filename="css/screen.css",
+            rewrite_path_re=CSS_REWRITE_PATH_RE,
         )
+
         self.assertEqual(
             """.embedded-url-svg {
   background-image: url("data:image/svg+xml;charset=utf8,%3Csvg viewBox='0 0 32 32' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath      stroke='rgba(255, 255, 255, 0.5)' stroke-width='2' stroke-linecap='round' stroke-miterlimit='10' d='M4 8h24M4 16h24M4 24h24'/%3E%     3C/svg%3E");
 }
 @font-face {
   font-family: 'Pipeline';
-  src: url(../pipeline/fonts/pipeline.eot);
-  src: url(../pipeline/fonts/pipeline.eot?#iefix) format('embedded-opentype');
-  src: local('☺'), url(../pipeline/fonts/pipeline.woff) format('woff'), url(../pipeline/fonts/pipeline.ttf) format('truetype'), url(../pipeline/fonts/pipeline.svg#IyfZbseF) format('svg');
+  src: url('../pipeline/fonts/pipeline.eot');
+  src: url('../pipeline/fonts/pipeline.eot?#iefix') format('embedded-opentype');
+  src: local('☺'), url('../pipeline/fonts/pipeline.woff') format('woff'), url('../pipeline/fonts/pipeline.ttf') format('truetype'), url('../pipeline/fonts/pipeline.svg#IyfZbseF') format('svg');
   font-weight: normal;
   font-style: normal;
 }
@@ -202,13 +211,272 @@ def test_url_rewrite(self):
             output,
         )
 
-    def test_url_rewrite_data_uri(self):
-        output = self.compressor.concatenate_and_rewrite(
+    def test_concatenate_with_url_rewrite_data_uri(self):
+        output = self.compressor.concatenate(
             [
                 _("pipeline/css/nested/nested.css"),
             ],
-            "pipeline/screen.css",
+            file_sep="",
+            output_filename="pipeline/screen.css",
+            rewrite_path_re=CSS_REWRITE_PATH_RE,
+        )
+
+        self.assertEqual(
+            """.data-url {
+  background-image: url(data:image/svg+xml;charset=US-ASCII,%3C%3Fxml%20version%3D%221.0%22%20encoding%3D%22iso-8859-1%22%3F%3E%3C!DOCTYPE%20svg%20PUBLIC%20%22-%2F%2FW3C%2F%2FDTD%20SVG%201.1%2F%2FEN%22%20%22http%3A%2F%2Fwww.w3.org%2FGraphics%2FSVG%2F1.1%2FDTD%2Fsvg11.dtd%22%3E%3Csvg%20version%3D%221.1%22%20id%3D%22Layer_1%22%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20xmlns%3Axlink%3D%22http%3A%2F%2Fwww.w3.org%2F1999%2Fxlink%22%20x%3D%220px%22%20y%3D%220px%22%20%20width%3D%2212px%22%20height%3D%2214px%22%20viewBox%3D%220%200%2012%2014%22%20style%3D%22enable-background%3Anew%200%200%2012%2014%3B%22%20xml%3Aspace%3D%22preserve%22%3E%3Cpath%20d%3D%22M11%2C6V5c0-2.762-2.239-5-5-5S1%2C2.238%2C1%2C5v1H0v8h12V6H11z%20M6.5%2C9.847V12h-1V9.847C5.207%2C9.673%2C5%2C9.366%2C5%2C9%20c0-0.553%2C0.448-1%2C1-1s1%2C0.447%2C1%2C1C7%2C9.366%2C6.793%2C9.673%2C6.5%2C9.847z%20M9%2C6H3V5c0-1.657%2C1.343-3%2C3-3s3%2C1.343%2C3%2C3V6z%22%2F%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3C%2Fsvg%3E);
+}
+.data-url-quoted {
+  background-image: url('data:image/svg+xml;charset=US-ASCII,%3C%3Fxml%20version%3D%221.0%22%20encoding%3D%22iso-8859-1%22%3F%3E%3C!DOCTYPE%20svg%20PUBLIC%20%22-%2F%2FW3C%2F%2FDTD%20SVG%201.1%2F%2FEN%22%20%22http%3A%2F%2Fwww.w3.org%2FGraphics%2FSVG%2F1.1%2FDTD%2Fsvg11.dtd%22%3E%3Csvg%20version%3D%221.1%22%20id%3D%22Layer_1%22%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20xmlns%3Axlink%3D%22http%3A%2F%2Fwww.w3.org%2F1999%2Fxlink%22%20x%3D%220px%22%20y%3D%220px%22%20%20width%3D%2212px%22%20height%3D%2214px%22%20viewBox%3D%220%200%2012%2014%22%20style%3D%22enable-background%3Anew%200%200%2012%2014%3B%22%20xml%3Aspace%3D%22preserve%22%3E%3Cpath%20d%3D%22M11%2C6V5c0-2.762-2.239-5-5-5S1%2C2.238%2C1%2C5v1H0v8h12V6H11z%20M6.5%2C9.847V12h-1V9.847C5.207%2C9.673%2C5%2C9.366%2C5%2C9%20c0-0.553%2C0.448-1%2C1-1s1%2C0.447%2C1%2C1C7%2C9.366%2C6.793%2C9.673%2C6.5%2C9.847z%20M9%2C6H3V5c0-1.657%2C1.343-3%2C3-3s3%2C1.343%2C3%2C3V6z%22%2F%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3C%2Fsvg%3E');
+}
+""",  # noqa
+            output,
+        )
+
+    def test_concatenate_css_with_sourcemap(self) -> None:
+        output = self.compressor.concatenate(
+            [
+                _("pipeline/css/sourcemap.css"),
+            ],
+            file_sep="",
+            output_filename="css/sourcemap-bundle.css",
+            rewrite_path_re=CSS_REWRITE_PATH_RE,
+        )
+
+        self.assertEqual(
+            output,
+            "div {\n"
+            "  display: inline;\n"
+            "}\n"
+            "\n"
+            "span {\n"
+            "  display: block;\n"
+            "}\n"
+            "\n"
+            "\n"
+            "//#  sourceMappingURL=../pipeline/css/sourcemap1.css.map\n"
+            "\n"
+            "//@ sourceMappingURL=../pipeline/css/sourcemap2.css.map  \n"
+            "\n"
+            "/*#  sourceMappingURL=../pipeline/css/sourcemap3.css.map */\n"
+            "\n"
+            "/*@ sourceMappingURL=../pipeline/css/sourcemap4.css.map  */\n"
+            "\n"
+            "//#  sourceURL=../pipeline/css/sourcemap5.css.map\n"
+            "\n"
+            "//@ sourceURL=../pipeline/css/sourcemap6.css.map  \n"
+            "\n"
+            "/*#  sourceURL=../pipeline/css/sourcemap7.css.map */\n"
+            "\n"
+            "/*@ sourceURL=../pipeline/css/sourcemap8.css.map  */\n",
+        )
+
+    def test_concatenate_js_with_sourcemap(self) -> None:
+        output = self.compressor.concatenate(
+            [
+                _("pipeline/js/sourcemap.js"),
+            ],
+            file_sep=";",
+            output_filename="js/sourcemap-bundle.js",
+            rewrite_path_re=JS_REWRITE_PATH_RE,
+        )
+
+        self.assertEqual(
+            output,
+            "const abc = 123;\n"
+            "\n"
+            "\n"
+            "//#  sourceMappingURL=../pipeline/js/sourcemap1.js.map\n"
+            "\n"
+            "//@ sourceMappingURL=../pipeline/js/sourcemap2.js.map  \n"
+            "\n"
+            "/*#  sourceMappingURL=../pipeline/js/sourcemap3.js.map */\n"
+            "\n"
+            "/*@ sourceMappingURL=../pipeline/js/sourcemap4.js.map  */\n"
+            "\n"
+            "//#  sourceURL=../pipeline/js/sourcemap5.js.map\n"
+            "\n"
+            "//@ sourceURL=../pipeline/js/sourcemap6.js.map  \n"
+            "\n"
+            "/*#  sourceURL=../pipeline/js/sourcemap7.js.map */\n"
+            "\n"
+            "/*@ sourceURL=../pipeline/js/sourcemap8.js.map  */\n",
+        )
+
+    def test_concatenate_without_rewrite_path_re(self) -> None:
+        message = (
+            "Compressor.concatenate() was called without passing "
+            "rewrite_path_re_= or output_filename=. If you are "
+            "specializing Compressor, please update your call "
+            "to remain compatible with future changes."
+        )
+
+        with self.assertWarnsMessage(DeprecationWarning, message):
+            output = self.compressor.concatenate(
+                [
+                    _("pipeline/js/sourcemap.js"),
+                ],
+                file_sep=";",
+                output_filename="js/sourcemap-bundle.js",
+            )
+
+        self.assertEqual(
+            output,
+            "const abc = 123;\n"
+            "\n"
+            "\n"
+            "//#  sourceMappingURL=sourcemap1.js.map\n"
+            "\n"
+            "//@ sourceMappingURL=sourcemap2.js.map  \n"
+            "\n"
+            "/*#  sourceMappingURL=sourcemap3.js.map */\n"
+            "\n"
+            "/*@ sourceMappingURL=sourcemap4.js.map  */\n"
+            "\n"
+            "//#  sourceURL=sourcemap5.js.map\n"
+            "\n"
+            "//@ sourceURL=sourcemap6.js.map  \n"
+            "\n"
+            "/*#  sourceURL=sourcemap7.js.map */\n"
+            "\n"
+            "/*@ sourceURL=sourcemap8.js.map  */\n",
+        )
+
+    def test_concatenate_without_output_filename(self) -> None:
+        message = (
+            "Compressor.concatenate() was called without passing "
+            "rewrite_path_re_= or output_filename=. If you are "
+            "specializing Compressor, please update your call "
+            "to remain compatible with future changes."
+        )
+
+        with self.assertWarnsMessage(DeprecationWarning, message):
+            output = self.compressor.concatenate(
+                [
+                    _("pipeline/js/sourcemap.js"),
+                ],
+                file_sep=";",
+                rewrite_path_re=JS_REWRITE_PATH_RE,
+            )
+
+        self.assertEqual(
+            output,
+            "const abc = 123;\n"
+            "\n"
+            "\n"
+            "//#  sourceMappingURL=sourcemap1.js.map\n"
+            "\n"
+            "//@ sourceMappingURL=sourcemap2.js.map  \n"
+            "\n"
+            "/*#  sourceMappingURL=sourcemap3.js.map */\n"
+            "\n"
+            "/*@ sourceMappingURL=sourcemap4.js.map  */\n"
+            "\n"
+            "//#  sourceURL=sourcemap5.js.map\n"
+            "\n"
+            "//@ sourceURL=sourcemap6.js.map  \n"
+            "\n"
+            "/*#  sourceURL=sourcemap7.js.map */\n"
+            "\n"
+            "/*@ sourceURL=sourcemap8.js.map  */\n",
+        )
+
+    def test_concatenate_without_file_sep(self) -> None:
+        message = (
+            "Compressor.concatenate() was called without passing "
+            "file_sep=. If you are specializing Compressor, please "
+            "update your call to remain compatible with future changes. "
+            "Defaulting to JavaScript behavior for "
+            "backwards-compatibility."
+        )
+
+        with self.assertWarnsMessage(DeprecationWarning, message):
+            output = self.compressor.concatenate(
+                [
+                    _("pipeline/js/first.js"),
+                    _("pipeline/js/second.js"),
+                ],
+                output_filename="js/sourcemap-bundle.js",
+                rewrite_path_re=JS_REWRITE_PATH_RE,
+            )
+
+        self.assertEqual(
+            output,
+            "(function() {\n"
+            "  window.concat = function() {\n"
+            "    console.log(arguments);\n"
+            "  }\n"
+            "}()) // No semicolon\n"
+            "\n"
+            ";(function() {\n"
+            "  window.cat = function() {\n"
+            '    console.log("hello world");\n'
+            "  }\n"
+            "}());\n",
+        )
+
+    def test_legacy_concatenate_and_rewrite(self) -> None:
+        message = (
+            "Compressor.concatenate_and_rewrite() is deprecated. Please "
+            "call concatenate() instead."
+        )
+
+        with self.assertWarnsMessage(DeprecationWarning, message):
+            output = self.compressor.concatenate_and_rewrite(
+                [
+                    _("pipeline/css/urls.css"),
+                ],
+                "css/screen.css",
+            )
+
+        self.assertEqual(
+            """.embedded-url-svg {
+  background-image: url("data:image/svg+xml;charset=utf8,%3Csvg viewBox='0 0 32 32' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath      stroke='rgba(255, 255, 255, 0.5)' stroke-width='2' stroke-linecap='round' stroke-miterlimit='10' d='M4 8h24M4 16h24M4 24h24'/%3E%     3C/svg%3E");
+}
+@font-face {
+  font-family: 'Pipeline';
+  src: url('../pipeline/fonts/pipeline.eot');
+  src: url('../pipeline/fonts/pipeline.eot?#iefix') format('embedded-opentype');
+  src: local('☺'), url('../pipeline/fonts/pipeline.woff') format('woff'), url('../pipeline/fonts/pipeline.ttf') format('truetype'), url('../pipeline/fonts/pipeline.svg#IyfZbseF') format('svg');
+  font-weight: normal;
+  font-style: normal;
+}
+.relative-url {
+  background-image: url(../pipeline/images/sprite-buttons.png);
+}
+.relative-url-querystring {
+  background-image: url(../pipeline/images/sprite-buttons.png?v=1.0#foo=bar);
+}
+.absolute-url {
+  background-image: url(/images/sprite-buttons.png);
+}
+.absolute-full-url {
+  background-image: url(http://localhost/images/sprite-buttons.png);
+}
+.no-protocol-url {
+  background-image: url(//images/sprite-buttons.png);
+}
+.anchor-tag-url {
+  background-image: url(#image-gradient);
+}
+@font-face{src:url(../pipeline/fonts/pipeline.eot);src:url(../pipeline/fonts/pipeline.eot?#iefix) format('embedded-opentype'),url(../pipeline/fonts/pipeline.woff) format('woff'),url(../pipeline/fonts/pipeline.ttf) format('truetype');}
+""",  # noqa
+            output,
         )
+
+    def test_legacy_concatenate_and_rewrite_with_data_uri(self) -> None:
+        message = (
+            "Compressor.concatenate_and_rewrite() is deprecated. Please "
+            "call concatenate() instead."
+        )
+
+        with self.assertWarnsMessage(DeprecationWarning, message):
+            output = self.compressor.concatenate_and_rewrite(
+                [
+                    _("pipeline/css/nested/nested.css"),
+                ],
+                "pipeline/screen.css",
+            )
+
         self.assertEqual(
             """.data-url {
   background-image: url(data:image/svg+xml;charset=US-ASCII,%3C%3Fxml%20version%3D%221.0%22%20encoding%3D%22iso-8859-1%22%3F%3E%3C!DOCTYPE%20svg%20PUBLIC%20%22-%2F%2FW3C%2F%2FDTD%20SVG%201.1%2F%2FEN%22%20%22http%3A%2F%2Fwww.w3.org%2FGraphics%2FSVG%2F1.1%2FDTD%2Fsvg11.dtd%22%3E%3Csvg%20version%3D%221.1%22%20id%3D%22Layer_1%22%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20xmlns%3Axlink%3D%22http%3A%2F%2Fwww.w3.org%2F1999%2Fxlink%22%20x%3D%220px%22%20y%3D%220px%22%20%20width%3D%2212px%22%20height%3D%2214px%22%20viewBox%3D%220%200%2012%2014%22%20style%3D%22enable-background%3Anew%200%200%2012%2014%3B%22%20xml%3Aspace%3D%22preserve%22%3E%3Cpath%20d%3D%22M11%2C6V5c0-2.762-2.239-5-5-5S1%2C2.238%2C1%2C5v1H0v8h12V6H11z%20M6.5%2C9.847V12h-1V9.847C5.207%2C9.673%2C5%2C9.366%2C5%2C9%20c0-0.553%2C0.448-1%2C1-1s1%2C0.447%2C1%2C1C7%2C9.366%2C6.793%2C9.673%2C6.5%2C9.847z%20M9%2C6H3V5c0-1.657%2C1.343-3%2C3-3s3%2C1.343%2C3%2C3V6z%22%2F%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3Cg%3E%3C%2Fg%3E%3C%2Fsvg%3E);