Add linkcheck_case_sensitive configuration option #14046

FazeelUsmani · 2025-11-07T15:07:09Z

This PR adds a new configuration option linkcheck_ignore_case to enable case-insensitive URL and anchor checking in the linkcheck builder.

Problem

Some web servers (e.g., GitHub, certain hosting platforms) are case-insensitive and may return URLs with different casing than the original link. This causes the linkcheck builder to report false-positive redirects when the URLs differ only in case, even though they point to the same resource.

Solution

Added linkcheck_ignore_case boolean configuration option (default: False)
Modified URL comparison logic to support case-insensitive matching when enabled
Modified anchor comparison in AnchorCheckParser to support case-insensitive matching when enabled
Added comprehensive tests for both URL and anchor case-insensitive checking
Updated documentation in doc/usage/configuration.rst

jayaddison · 2025-11-08T12:18:26Z

Hi @FazeelUsmani - thank you for developing and describing this pull request.

I have a concern that enabling the option reduces the precision of other hyperlinks that are checked.

Could you explain the use case where it would be easier for a documentation project to enable this option by editing the conf.py instead of fixing the URLs/anchors in their documentation sources to use the correct casing?

FazeelUsmani · 2025-11-10T09:00:09Z

That’s a good point, @jayaddison.
This option is off by default and meant mainly only for large or older docs where many links hit servers that normalise URL casing (like GitHub) or are case-insensitive (like Windows). Enabling it just filters out harmless casing-related redirects so teams can focus on real link issues instead of noise.

jayaddison · 2025-11-10T10:54:57Z

@FazeelUsmani got it, understood. As often happens, I had a misunderstanding to begin with - you are saying that this only affects whether case-adjusted response URLs are considered to be redirect instead of successful.

Let me think about this a little more; I do understand the value in this now, but am wary of (and trying to think of) any problem side-effects.

jayaddison · 2025-11-10T10:55:11Z

(also, thank you for the explanation)

jayaddison · 2025-11-10T10:56:46Z

Separately: I do think that we should probably isolate the redirect-case-sensitivity handling from the HTML anchor case-sensitivity; they seem fairly functionally different from each other to me.

FazeelUsmani · 2025-11-10T17:32:42Z

Hmm.. makes sense. I can refactor this into two separate options:
linkcheck_ignore_case_urls: For comparing URL paths (the redirect scenario)
linkcheck_ignore_case_anchors: For comparing HTML anchors

This would give users more granular control. Most users would likely want linkcheck_ignore_case_urls = True (for case-insensitive servers) while keeping linkcheck_ignore_case_anchors = False (since HTML IDs are technically case-sensitive per spec). What do you say?

AA-Turner · 2025-11-10T19:05:59Z

Two options seems overkill for this use-case. What do browsers do de facto on case mismatches on fragment IDs?

A

FazeelUsmani · 2025-11-11T08:46:44Z

Fair point — browsers generally treat fragment IDs as case-sensitive, though behavior can vary depending on the HTML generator. My thought was mainly to avoid false negatives in edge cases (like auto-generated anchors that normalize casing differently).
That said, I’m fine keeping it as a single option if we note the anchor behavior clearly in the docs.

jayaddison · 2025-11-11T10:14:55Z

I can't think of drawbacks to the redirect case-folding -- and although it's maybe slightly controversial, I wonder whether we should enable it by default.

The anchor-checking I'm less certain about; given that we believe browsers seem to navigate to anchors case-sensitively -- something I too checked locally and that is certainly the case in Firefox 140.4 -- I'd be reluctant to offer that without a demonstrable use-case (again that can't be solved easily by fixing the source documentation).

FazeelUsmani · 2025-11-11T12:09:35Z

That makes sense — I’ll keep it as a single linkcheck_ignore_case option limited to the URL path. Anchor checks will remain case-sensitive to align with browser behavior, and I’ll clarify this distinction in the docs so users understand the expected behavior.

jayaddison · 2025-11-11T12:29:38Z

Sounds good to me! Thanks @FazeelUsmani.

jayaddison · 2025-11-17T20:52:45Z

tests/test_builders/test_build_linkcheck.py

+    # With case-sensitive checking, a URL that redirects to different case
+    # should be marked as redirected
+    lowercase_uri = f'http://{address}/path'
+    if lowercase_uri in rowsby:


When I run the tests locally, the code inside this if condition isn't being evaluated - so I think the test coverage is incomplete?

Hmmm... let me check.

Yes, the test document didn't contain a link to /path.
I've created a dedicated test root (test-linkcheck-case-check) with a link to the /path endpoint and changed the conditional check to an assertion so the test will fail if the URL isn't being checked.

jayaddison · 2025-11-18T10:37:52Z

tests/test_builders/test_build_linkcheck.py

+        def mock_request(self, method, url, **kwargs):
+            response = original_request(self, method, url, **kwargs)
+            # Change the URL to uppercase to simulate server behavior
+            if '/path' in str(response.url).lower():
+                response.url = str(response.url).replace('/path', '/PATH')
+            return response


This approach of mocking/intercepting the HTTP response object bypasses some of the logic that we want to test.

Instead let's rewrite the CaseSensitiveHandler HTTP server so that when /path is requested, we redirect the client to /Path -- and then the test should be able to confirm (without mocking/patching) how the linkcheck builder handles that.

Done! I've rewritten CaseSensitiveHandler to perform an actual HTTP 301 redirect from /path to /Path, and removed all the mocking/patching code. The test now correctly validates the redirect detection logic without bypassing any of the implementation.

jayaddison · 2025-11-18T11:08:12Z

doc/usage/configuration.rst

+.. confval:: linkcheck_case_insensitive
+   :type: :code-py:`bool`
+   :default: :code-py:`False`
+
+   When :code-py:`True`, the *linkcheck* builder will compare URL paths
+   case-insensitively when checking for redirects.
+   This is useful for checking links on case-insensitive servers
+   (for example, GitHub, Windows-based servers, or certain hosting platforms)
+   that may return URLs with different case than the original link.
+
+   When enabled, URL paths like ``/Path`` and ``/path`` are considered
+   equivalent, preventing false-positive redirect warnings on
+   case-insensitive servers.
+
+   .. note::
+
+      This option only affects URL path comparison for redirect detection.
+      HTML anchor checking remains case-sensitive to match browser behavior,
+      where fragment identifiers (``#anchor``) are case-sensitive per the
+      HTML specification.
+
+   Example:
+
+   .. code-block:: python
+
+      linkcheck_case_insensitive = True
+
+   .. versionadded:: 8.2
+


This may be my perception, but I would suggest that it may be easier to understand the config setting if we remove the inverse prefix (e.g. using sensitive instead of insensitive).

I also have a few ideas for the documentation text; please let me know what you think:

Suggested change

.. confval:: linkcheck_case_insensitive

:type: :code-py:`bool`

:default: :code-py:`False`

When :code-py:`True`, the *linkcheck* builder will compare URL paths

case-insensitively when checking for redirects.

This is useful for checking links on case-insensitive servers

(for example, GitHub, Windows-based servers, or certain hosting platforms)

that may return URLs with different case than the original link.

When enabled, URL paths like ``/Path`` and ``/path`` are considered

equivalent, preventing false-positive redirect warnings on

case-insensitive servers.

.. note::

This option only affects URL path comparison for redirect detection.

HTML anchor checking remains case-sensitive to match browser behavior,

where fragment identifiers (``#anchor``) are case-sensitive per the

HTML specification.

Example:

.. code-block:: python

linkcheck_case_insensitive = True

.. versionadded:: 8.2

.. confval:: linkcheck_case_sensitive

:type: :code-py:`bool`

:default: :code-py:`True`

This setting controls how the *linkcheck* builder decides

whether a hyperlink's destination is the same as the URL

written in the documentation.

By default, *linkcheck* requires the destination URL to match the written URL case-sensitively. This means that a link to ``http://webserver.test/USERNAME`` in

the documentation that the server redirects to ``http://webserver.test/username`` will be reported as ``redirected``.

To allow a more lenient URL comparison, that will report the previous case as

as ``working`` instead, configure this setting to ``False``.

.. note::

HTML anchor checking is always case-sensitive, and is

not affected by this setting.

.. versionadded:: 8.2

Edit: replace status code of successful with the actual value from the code, working.

I've applied your documentation changes.

Thanks again!

jayaddison · 2025-11-18T11:19:58Z

sphinx/builders/linkcheck.py

+            if self.case_insensitive:
+                normalised_url = normalised_url.casefold()


This is probably a rare scenario, but strictly speaking I think we should avoid casefolding any fragment/anchor identifier part of the URL.

e.g.

❌ /USERNAME#Badges -> /username#badges

✅ /USERNAME#Badges -> /username#Badges

(I only realised this after attempting to rewrite the config setting documentation in my own words -- in particular the part about anchor case-sensitivity)

Right. I've fixed the _normalise_url() function to only casefold the URL before the fragment. Now /USERNAME#Badges correctly becomes /username#Badges (preserving the fragment case). The function now splits on # and only applies .casefold() to the URL part.

OK; the updated URL normalisation logic looks good to me; thank you.

…andling

jayaddison · 2025-11-18T12:42:18Z

sphinx/builders/linkcheck.py

    app.add_event('linkcheck-process-uri')

    # priority 900 to happen after ``check_confval_types()``
+    app.connect('config-inited', handle_deprecated_linkcheck_case_config, priority=899)


We don't need to add any deprecation/migration-handling code for this config setting, because the linkcheck_case_insensitive config setting has not been included in a published release of Sphinx.

I've removed the deprecation handler function and the old config value registration.

tests/test_builders/test_build_linkcheck.py

Co-authored-by: James Addison <[email protected]>

…sphinx into linkcheck_case_insensitive

jayaddison · 2025-11-18T12:53:16Z

tests/test_builders/test_build_linkcheck.py

+    def do_HEAD(self):
+        if self.path == '/path':
+            # Redirect lowercase /path to uppercase /Path
+            self.send_response(301, 'Moved Permanently')
+            self.send_header('Location', '/Path')
+            self.send_header('Content-Length', '0')
+            self.end_headers()
+        elif self.path == '/Path':
+            self.send_response(200, 'OK')
+            self.send_header('Content-Length', '0')
+            self.end_headers()
+        else:
+            self.send_response(404, 'Not Found')
+            self.send_header('Content-Length', '0')
+            self.end_headers()


We can remove the do_HEAD code block here, as the base HTTP server will invoke do_GET instead if it's missing.

NB: Let's also apply the Location response header simplification to do_GET when we do that, though.

Good point! I've removed the do_HEAD method entirely - the base HTTP server will invoke do_GET instead. I've also simplified the Location header in do_GET to just use /Path instead of the full URL with host.

jayaddison · 2025-11-18T12:58:09Z

tests/test_builders/test_build_linkcheck.py

    } in content
+
+
+class CaseSensitiveHandler(BaseHTTPRequestHandler):


Slightly nitpicky, but: the client and the test case are about case sensitivity -- but this handler is not really. What it does is to normalise/capitalise the path. So I'd suggest renaming it:

Suggested change

class CaseSensitiveHandler(BaseHTTPRequestHandler):

class CapitalisePathHandler(BaseHTTPRequestHandler):

Renamed it from CaseSensitiveHandler to CapitalisePathHandler and updated the docstring to reflect what it actually does.

jayaddison · 2025-11-18T12:59:58Z

tests/test_builders/test_build_linkcheck.py

+    lowercase_uri = f'http://{address}/path'
+    assert lowercase_uri in rowsby, f'Expected {lowercase_uri} to be checked'
+    assert rowsby[lowercase_uri]['status'] == 'redirected'


Although the containment check is good defensive coding, we don't perform similar checks in the other tests, so for consistency I would recommend:

Suggested change

lowercase_uri = f'http://{address}/path'

assert lowercase_uri in rowsby, f'Expected {lowercase_uri} to be checked'

assert rowsby[lowercase_uri]['status'] == 'redirected'

assert rowsby[f'http://{address}/path']['status'] == 'redirected'

(I briefly considered suggesting renaming the variable to something like origin_url, outbound_url or documented_url -- but on balance I think we should simply omit it)

I've simplified both tests to directly assert on rowsby[f'http://{address}/path']['status'] without the intermediate variable or defensive containment check, matching the style used in other tests in the file

…plify assertions

jayaddison · 2025-11-18T13:13:30Z

Ok, I think this is looking pretty good @FazeelUsmani - thanks for accommodating my feedback.

The only significant remaining question I have is whether this should be controlled as a single boolean value, or whether it should be enabled for patterns of URLs -- similar to the way that linkcheck_auth and linkcheck_ignore can be configured for specific patterns.

Currently: I am leaning towards the idea that, ideally, documentation projects should only enable this for the domains/websites where they need the tolerance for case-normalising redirects.

The reason I lean that way is that -- generally -- URLs are in fact case sensitive, and so I have some lingering doubts about making this a flag that is likely to affect cases where it's not worthwhile to casefold.

PS: either way, if you could also update the title of this PR that would be great!

FazeelUsmani · 2025-11-18T13:26:45Z

Thanks for the feedback @jayaddison!

That's a really good point about making this pattern-based rather than a global boolean. I can see how that would be safer and more precise - only applying case-insensitivity to domains that actually need it (like GitHub), similar to how linkcheck_auth and linkcheck_ignore work.

So, the pattern-based approach would be something like:

linkcheck_case_sensitive_patterns = {
    r'https://github\.com/.*': False,
}

Does this sounds good to you?

jayaddison · 2025-11-18T13:44:44Z

That mostly sounds good - I would suggest some adjustments, though: either:

Rename the config dictionary's name to linkcheck_case_sensitivity -- for consistency with the auth and ignore settings, that omit the word patterns.

OR

Use a list datastructure instead of a dict, and rename the variable to linkcheck_case_insensitive (my mistake - perhaps I should not have suggested removing the in... prefix earlier! if we choose this route, I think it'd make sense again because it'd be describing a collection of opt-in patterns that disable the default case-sensitive behaviour)

I don't have a strong preference yet -- I'm continuing to think about it.

The second option might make it slightly more apparent to readers that these ~~domains~~ patterns are exceptions and that case-sensitive URL comparison is the default.

Edit: fixup: the matching patterns are not necessarily domains.

FazeelUsmani · 2025-11-18T13:53:13Z

Thanks for clarifying, @jayaddison! I'll go with Option 2 - using a list with linkcheck_case_insensitive. I agree it makes the intent clearer: these are opt-in patterns for URLs that should be treated case-insensitively, with case-sensitive being the default.

So the config would look like:

linkcheck_case_insensitive = [
    r'https://github\.com/.*',
]

Does that sound good to you? I'll start refactoring to implement pattern matching once you confirm.

jayaddison · 2025-11-18T14:37:18Z

@FazeelUsmani yep, that sounds good to me 👍

jayaddison · 2025-11-18T19:09:56Z

tests/test_builders/test_build_linkcheck.py

+    freshenv=True,
+    confoverrides={'linkcheck_case_insensitive': [r'http://localhost:\d+/.*']},
+)
+def test_linkcheck_case_insensitive(app: SphinxTestApp) -> None:


Optional: I think it would be possible to merge the two test cases into a single def test_linkcheck_case_sensitivity now that we can pattern-match different URL patterns.

(the code for the two of them is very similar currently, so perhaps the end result would be neater/smaller by combining them)

jayaddison · 2025-11-18T19:10:28Z

tests/test_builders/test_build_html_numfig.py



 @pytest.mark.sphinx('html', testroot='numfig')
-@pytest.mark.test_params(shared_result='test_build_html_numfig')


Let's make sure to restore this pytest marker (I think you did, but maybe it got removed again somehow).

jayaddison · 2025-11-18T19:47:15Z

Ah, and one more thing: please make sure to update CHANGES.rst to describe your change and add a credit entry for it!

I think it's looking good; we'll also need a core developer/maintainer to approve it, and I can't promise if/when that will be.

FazeelUsmani added 6 commits November 7, 2025 20:24

Update configuration.rst

63e108c

Add linkcheck_ignore_case config option

caae7eb

Update i18n.py

9e6dd40

fixed the failing test test_numfig_disabled_warn

eccd6d7

Enable case-insensitive URL and anchor checking for linkcheck builder

6300483

strip ANSI color codes from stderr before assertion

b61366c

FazeelUsmani marked this pull request as draft November 7, 2025 15:08

FazeelUsmani added 2 commits November 7, 2025 21:42

fixed the failing test test_connect_to_selfsigned_fails

7ea45c6

Update test_build_linkcheck.py

99a5dc0

sylvainstjean53-creator approved these changes Nov 9, 2025

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Merge branch 'master' into linkcheck_case_insensitive

f99651f

FazeelUsmani marked this pull request as ready for review November 10, 2025 08:56

Update linkcheck.py

ac12d63

FazeelUsmani marked this pull request as draft November 11, 2025 13:13

FazeelUsmani added 2 commits November 11, 2025 18:45

Update test_build_linkcheck.py

1a0d9ed

Update test_build_linkcheck.py

d115b1e

FazeelUsmani force-pushed the linkcheck_case_insensitive branch 3 times, most recently from 56d6a63 to d115b1e Compare November 11, 2025 14:31

FazeelUsmani requested review from AA-Turner and jayaddison November 17, 2025 13:16

Remove unused test parameter from numfig test

66ae54d

jayaddison suggested changes Nov 17, 2025

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Tests: Add complete coverage for linkcheck case sensitivity tests

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FazeelUsmani requested a review from jayaddison November 18, 2025 09:37

jayaddison reviewed Nov 18, 2025

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FazeelUsmani added 2 commits November 18, 2025 17:44

Refactor linkcheck case sensitivity: rename config and fix fragment h…

eaa1caa

…andling

Improve formatting and update config value handling

57e8b3c

jayaddison reviewed Nov 18, 2025

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tests/test_builders/test_build_linkcheck.py Outdated Show resolved Hide resolved

FazeelUsmani and others added 3 commits November 18, 2025 18:16

Update tests/test_builders/test_build_linkcheck.py

5dffff4

Co-authored-by: James Addison <[email protected]>

Remove deprecated linkcheck_case_insensitive config handling

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Merge branch 'linkcheck_case_insensitive' of github.com:FazeelUsmani/…

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…sphinx into linkcheck_case_insensitive

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Refactor linkcheck tests: rename handler for case sensitivity and sim…

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…plify assertions

FazeelUsmani changed the title ~~Add linkcheck_ignore_case configuration option~~ Add linkcheck_case_sensitive configuration option Nov 18, 2025

Add support for case-insensitive URL checking in linkcheck builder

5615ffc

jayaddison reviewed Nov 18, 2025

View reviewed changes

		if self.case_insensitive:
		normalised_url = normalised_url.casefold()

		} in content


		class CaseSensitiveHandler(BaseHTTPRequestHandler):

	class CaseSensitiveHandler(BaseHTTPRequestHandler):
	class CapitalisePathHandler(BaseHTTPRequestHandler):



		@pytest.mark.sphinx('html', testroot='numfig')
		@pytest.mark.test_params(shared_result='test_build_html_numfig')

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