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Checking Anchor Links (Fragment Identifiers)

lychee can check anchor links (also called fragments) in both HTML and Markdown files. This feature helps ensure that internal links to specific sections of a page are valid.

Quick Start

To enable anchor link checking, use the --include-fragments flag:

Terminal window
lychee --include-fragments 'https://example.com/docs'

Supported Formats Overview

FeatureMarkdownHTMLInline HTML in Markdown
Heading-based fragments✅✅✅
Custom ID fragments✅✅✅
Unicode in fragments✅✅✅
Inline code in headings✅N/AN/A

Detailed Information

Supported Formats

  • Markdown (.md) files
  • HTML (.html) files
  • Inline HTML within Markdown files
  • Links to headings (e.g., #introduction)
  • Links to custom IDs (e.g., #custom-section-id)
  • Unicode characters in fragments (e.g., #résumé)

How does lychee generate fragments for comparison?

lychee uses two main methods:

  1. Heading Attributes: For explicit IDs specified in Markdown (e.g., ## My Heading {#custom-id})
  2. Unique Kebab Case: For standard headings, similar to GitHub’s auto-generated anchors

Supported Edge Cases

lychee handles:

  • Headings with inline code (e.g., # `code` in heading)
  • Unicode characters in headings
  • Underscores in headings (preserved in fragments)

Limitations

  • Complex or nested HTML structures might not be fully supported
  • JavaScript-generated anchors cannot be checked
  • Some advanced Markdown or HTML processor-specific features may not be recognized. Create an issue if you encounter any problems.

Troubleshooting

In case of issues with anchor link checking, here are some tips:

  • Use explicit IDs for complex headings or when targeting specific elements
  • Ensure your Markdown and HTML follow standard practices for heading structures
  • For HTML files, use the id attribute on elements you want to link to