Markdown Link Checker — Find Broken Doc Links

Catch broken doc links before publish — offline, no external fetching.

What it checks (6 rules):

• Broken local file links (broken-local-link)
• Anchors with no matching heading (broken-anchor)
• Reference-style links with no definition (undefined-reference)
• Empty link text and empty link targets (empty-link-text, empty-link-target)
• Images without alt text (missing-alt-text)

Results: deterministic pass/fail, critical vs warning severities, CI-friendly exit codes, JSON and Markdown reports. Single file or recursive directory checking. Links inside fenced code blocks and inline code spans are ignored. External links are counted, never fetched or echoed.

Evidence: 7 automated tests, verified on real Markdown inputs before listing. Python 3.9+, no external dependencies.

Honest limits: does not fetch or verify external URLs, does not check setext-style headings, does not anchor-check pure-anchor reference definitions.

Part of the Safety Gate family — also see OpenAPI Linter when it ships.