⌘ K
finds in-doc heading links that don't resolve

Find broken Markdown anchors

Scan a Markdown document for in-document heading links (#some-heading) that no longer resolve — typos, renamed sections, or anchor drift after refactors.

Broken Anchor Checker
Input
192 B
15 lines
Output
76 B
7 lines
Status
ready
live
Ratio
0.40×
out/in
input · markdown
output · anchor report
Broken: [missing](#nope)

Known anchors:
  intro
  reference
  setup
  usage
Quick Start

How to check Markdown anchors

Builds a set of GitHub-style auto-anchors from every heading plus explicit <a id> tags, then flags any [link](#anchor) that doesn't resolve.

  1. 01

    Paste Markdown

    Headings and intra-doc links.

    Parsing runs through marked with GFM extensions enabled — tables, task lists, strikethrough, and fenced code blocks all match GitHub’s rendering.

    inputGFMmarkedCommonMarklive
    input · markdownmd · GFM
    # Setup
[go](#setup)
    loaded · GFMGFM · ready
  2. 02

    Build anchor set

    Every heading is slugified GitHub-style; explicit anchors are also added.

    Soft-break behaviour is configurable: by default a single newline becomes a space (CommonMark), toggle on for chat-style <br> insertion.

    indexsoft-breaksoptionsconfiglive
    anchors · optionsset · live
    {setup, intro}
    options applied · livelive
  3. 03

    Verify links

    Each #anchor reference is checked against the set.

    The preview is scoped under a .mde class so its CSS doesn’t bleed into the rest of the page. Output HTML is whitespace-controlled for clean diffs.

    checkpreviewscoped CSSrenderstable
    check · renderedfail · ready
    Broken: [x](#nope)
    rendered · liverendered
  4. 04

    Fix and ship

    Rename anchors or update links until the report is clean.

    Export covers both raw Markdown and rendered HTML; downloads stream as text/markdown or text/html via Blob + object URL.

    fixclipboard.md.htmlblob
    ✓ · exportedok · done
    ✓ All resolve
    shipped · ready to shipsuccess
Pro tips

Author Markdown that renders everywhere

GFM is the safe default

GitHub-Flavored Markdown is the de-facto baseline (tables, task lists, strikethrough). CommonMark is stricter but ubiquitous as a fallback.

Soft-break behaviour varies

A single newline is a space in CommonMark, a <br> in GFM. Toggle soft breaks when source matters.

Escape inside code fences

Backticks inside fenced blocks need a longer fence — three becomes four. Use ~~~ if your content has many backticks.

Anchors are slugified

GitHub lowercases, strips punctuation, and joins with hyphens. Duplicate headings get -1, -2 suffixes.

Tables need a header row

The dash row sets alignment (:---, :-:, ---:). Use Table Aligner for diff-friendly columns.

Front matter is YAML

Triple-dash blocks at the top of files are parsed by static-site generators. Use the Front-Matter Validator to catch syntax errors.

Related toolsAnchorsDupesTOCLinterHeading LevelerEditor
Use Cases

When to check anchors

Catch silent anchor drift before users land on a 404 jump.

Doc refactors

After renaming headings, sweep all #links. Render path uses marked with GFM extensions enabled (tables, task lists, strikethrough, autolinks), so what you preview matches what GitHub publishes bit-for-bit. Soft-break behaviour is configurable for chat-style vs prose Markdown.

GFM-compliant

README hygiene

Keep table-of-contents anchors honest. Pairs cleanly with the Markdown Cheatsheet for syntax you can't quite remember — callout blocks, footnotes, definition lists. Output stays diff-friendly so style-only changes don't drown out real edits in PRs.

GitHub-perfect

Site build CI

Pre-build check for static-site generators. Cross-platform safe: anchors, code fences, and tables behave identically on GitHub, GitLab, Bitbucket, and Gitea. Heading-anchor slugs follow GitHub's lowercase-and-hyphenate rules so deep links survive a docs migration.

diff-friendly

Wiki migration

Verify after import from Confluence / Notion. No server roundtrip — perfect for proprietary content you can't paste into a public tool. The full marked + GFM bundle ships with the page, so it works offline once loaded.

render-stable

Audit prep

Run before doc audits to surface stale links. Front matter (YAML / TOML / JSON) passes through unchanged so static-site pipelines (Jekyll, Hugo, Astro, Eleventy) read it correctly. Pair with the Front-Matter Validator to catch syntax errors before deploy.

cross-platform

Public docs

Avoid broken jumps from search results. Output is reproducible: identical input always produces identical Markdown, so doc-generation scripts can rely on it for snapshot tests and embedded into release workflows.

SEO-friendly
FAQ

Frequently asked questions

GitHub-style auto-anchors from heading text, plus explicit HTML id attributes on <a> tags.
Second and later occurrences get a -1, -2, ... suffix — matching GitHub's rendering.
No — only in-doc links of the form [text](#anchor). Use a link checker for external URLs.
No. Run against the final rendered doc if you assemble from partials.
No. Everything runs locally in your browser.
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