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[GH-ISSUE #253] Warn against dead links within the document #217

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opened 2026-03-03 01:24:48 +03:00 by kerem · 5 comments

kerem commented

2026-03-03 01:24:48 +03:00

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Originally created by @ben-clayton on GitHub (Feb 12, 2020).
Original GitHub issue: https://github.com/DavidAnson/markdownlint/issues/253

It would be fantastic if bad anchor-style links were detected and warned.
I wouldn't expect bad external URL links to be caught.

Originally created by @ben-clayton on GitHub (Feb 12, 2020). Original GitHub issue: https://github.com/DavidAnson/markdownlint/issues/253 It would be fantastic if bad anchor-style links were detected and warned. I wouldn't expect bad external URL links to be caught.

kerem

2026-03-03 01:24:48 +03:00

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kerem commented

2026-03-03 01:24:49 +03:00

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@koppor commented on GitHub (Apr 29, 2020):

Dead external links can be discovered with markdown-link-check:

One file: npx markdown-link-check README.md.

Multiple files outputting the result into a text file:

find . -name \*.md -exec npx markdown-link-check -qq {} \; > bad-links.txt

Note that I used npx to avoid explicit global installation of the markdown-link-check package.

@koppor commented on GitHub (Apr 29, 2020): Dead external links can be discovered with [markdown-link-check](https://github.com/tcort/markdown-link-check): One file: `npx markdown-link-check README.md`. Multiple files outputting the result into a text file: ```bash find . -name \*.md -exec npx markdown-link-check -qq {} \; > bad-links.txt ``` Note that I used [npx](https://www.npmjs.com/package/npx) to avoid explicit global installation of the markdown-link-check package.

kerem commented

2026-03-03 01:24:49 +03:00

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@nichtich commented on GitHub (Jun 29, 2020):

Thanks for the pointer to markdown-link-check, but I'd prefer to have basic support as part of markdownlint instead of having to use yet another tool with different usage and a lot of functionality I don't need anyway. The dead-links use case in this issue is anchor-style links, so implementation would be:

extract all heading titles and create anchor ids
extract all link targets starting with # and check whether a matching id exists.

Note this would not catch link targets within inline HTML but this is discouraged by MD033 anyway.

@nichtich commented on GitHub (Jun 29, 2020): Thanks for the pointer to markdown-link-check, but I'd prefer to have basic support as part of markdownlint instead of having to use yet another tool with different usage and a lot of functionality I don't need anyway. The dead-links use case in this issue is anchor-style links, so implementation would be: 1. extract all heading titles and [create anchor ids](https://github.com/markedjs/marked/blob/743ec55fe16e0b829f68db0b6b3cde9c0b23e78a/src/Slugger.js#L12) 2. extract all link targets starting with `#` and check whether a matching id exists. Note this would not catch link targets within inline HTML but this is [discouraged by MD033](https://github.com/DavidAnson/markdownlint/blob/main/doc/Rules.md#md033) anyway.

kerem commented

2026-03-03 01:24:49 +03:00

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@DavidAnson commented on GitHub (Jun 29, 2020):

@nichtich Is the anchor ID algorithm part of a specification anywhere, or are you suggesting making this specific to GitHub?

@DavidAnson commented on GitHub (Jun 29, 2020): @nichtich Is the anchor ID algorithm part of a specification anywhere, or are you suggesting making this specific to GitHub?

kerem commented

2026-03-03 01:24:49 +03:00

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@nichtich commented on GitHub (Jun 29, 2020):

Anchor links from header titles have been discussed in CommonMark but it's not part of CommonMark. Popular implementations that create anchor ids from header titles include Pandoc and GitHub. Pandoc also supports GitHub algorithm (see feature gfm_auto_identifiers), so GitHub algorithm seems the best choice:

spaces are converted to dashes (-)
uppercase characters are converted to lowercase characters
punctuation characters other than - and _ are removed
if nothing is left, use the identifier section

For a more extensive comparison of algorithms see https://babelmark.github.io/

@nichtich commented on GitHub (Jun 29, 2020): Anchor links from header titles [have been discussed in CommonMark](https://talk.commonmark.org/t/feature-request-automatically-generated-ids-for-headers/) but it's not part of CommonMark. Popular implementations that create anchor ids from header titles [include Pandoc](https://pandoc.org/MANUAL.html#headings-and-sections) and GitHub. Pandoc also supports GitHub algorithm (see feature `gfm_auto_identifiers`), so GitHub algorithm seems the best choice: * spaces are converted to dashes (`-`) * uppercase characters are converted to lowercase characters * punctuation characters other than `-` and `_` are removed * if nothing is left, use the identifier `section` For a more extensive comparison of algorithms see <https://babelmark.github.io/>

kerem commented

2026-03-03 01:24:49 +03:00

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@DavidAnson commented on GitHub (Jun 29, 2020):

Great info, thank you!

@DavidAnson commented on GitHub (Jun 29, 2020): Great info, thank you!

kerem referenced this issue

2026-03-07 20:03:53 +03:00

[GH-ISSUE #217] MD014 only handles the first instance of $ command in a group #2033