lychee link checking action

Quickly check links in Markdown, HTML, and text files using lychee.

When used in conjunction with Create Issue From File, issues will be opened when the action finds link problems.

Usage

Here is a full example of a GitHub workflow file:

It will check all repository links once per day and create an issue in case of errors. Save this under .github/workflows/links.yml:

name: Links

on:
  repository_dispatch:
  workflow_dispatch:
  schedule:
    - cron: "00 18 * * *"

jobs:
  linkChecker:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3

      - name: Link Checker
        id: lychee
        uses: lycheeverse/[email protected]

      - name: Create Issue From File
        if: env.lychee_exit_code != 0
        uses: peter-evans/create-issue-from-file@v4
        with:
          title: Link Checker Report
          content-filepath: ./lychee/out.md
          labels: report, automated issue

If you always want to use the latest features but avoid breaking changes, you can replace the version with lycheeverse/lychee-action@v1.

Alternative approach:

This will check all repository links during any git push event and for all pull requests. If there's an error, it will fail the action. This has the benefit of ensuring that during a Pull Request, no link is added that is broken and any existing link will be caught if they become broken. Save this under .github/workflows/links-fail-fast.yml:

name: Links (Fail Fast)

on:
  push:
  pull_request:

jobs:
  linkChecker:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3

      - name: Link Checker
        uses: lycheeverse/[email protected]
        with:
          fail: true

Passing arguments

This action uses lychee for link checking. lychee arguments can be passed to the action via the args parameter.

On top of that, the action also supports some additional arguments.

See action.yml for a full list of supported arguments and their default values.

Passing arguments

Here is how to pass the arguments.

- name: Link Checker
  uses: lycheeverse/[email protected]
  with:
    # Check all markdown and html files in repo (default)
    args: --verbose --no-progress './**/*.md' './**/*.html' './**/*.rst'
    # Use json as output format (instead of markdown)
    format: json
    # Use different output file path
    output: /tmp/foo.txt
    # Use a custom GitHub token, which 
    token: ${{ secrets.CUSTOM_TOKEN }}
    # Fail action on broken links
    fail: true

(If you need a token that requires permissions that aren't available in the default GITHUB_TOKEN, you can create a personal access token and pass it to the action via the token parameter.)

Utilising the cache feature

In order to mitigate issues regarding rate limiting or to reduce stress on external resources, one can setup lychee's cache similar to this:

- name: Restore lychee cache
  uses: actions/cache@v3
  with:
    path: .lycheecache
    key: cache-lychee-${{ github.sha }}
    restore-keys: cache-lychee-

- name: Run lychee
  uses: lycheeverse/[email protected]
  with:
    args: "--cache --max-cache-age 1d ."

It will compare and save the cache based on the given key. So in this setup, as long as a user triggers the CI run from the same commit, it will be the same key. The first run will save the cache, subsequent runs will not update it (because it's the same commit hash). For restoring the cache, the most recent available one is used (commit hash doesn't matter).

If you need more control over when caches are restored and saved, you can split the cache step and e.g. ensure to always save the cache (also when the link check step fails):

- name: Restore lychee cache
  id: restore-cache
  uses: actions/cache/restore@v3
  with:
    path: .lycheecache
    key: cache-lychee-${{ github.sha }}
    restore-keys: cache-lychee-

- name: Run lychee
  uses: lycheeverse/[email protected]
  with:
    args: "--cache --max-cache-age 1d ."

- name: Save lychee cache
  uses: actions/cache/save@v3
  if: always()
  with:
    path: .lycheecache
    key: ${{ steps.restore-cache.outputs.cache-primary-key }}

Excluding links from getting checked

Add a .lycheeignore file to the root of your repository to exclude links from getting checked. It supports regular expressions. One expression per line.

Fancy badge

Pro tip: You can add a little badge to your repo to show the status of your links. Just replace org with your organisation name and repo with the repository name and put it into your README.md:

[![Check Links](https://github.com/org/repo/actions/workflows/links.yml/badge.svg)](https://github.com/org/repo/actions/workflows/links.yml)

It will look like this:

Troubleshooting and common problems

See lychee's Troubleshooting Guide for solutions to common link-checking problems.

Performance

A full CI run to scan 576 links takes approximately 1 minute for the analysis-tools-dev/static-analysis repository.

Security and Updates

It is recommended to pin lychee-action to a fixed version for security reasons. You can use dependabot to automatically keep your GitHub actions up-to-date. This is a great way to pin lychee-action, while still receiving updates in the future. It's a relatively easy thing to do.

Create a file named .github/dependabot.yml with the following contents:

version: 2
updates:
  - package-ecosystem: "github-actions"
    directory: ".github/workflows"
    schedule:
      interval: "daily"

When you add or update the dependabot.yml file, this triggers an immediate check for version updates. Please see the documentation for all configuration options.

Security tip

For additional security when relying on automation to update actions you can pin the action to a SHA-256 rather than the semver version so as to avoid tag spoofing Dependabot will still be able to automatically update this.

For example:

- name: Link Checker
  uses: lycheeverse/lychee-action@ec7614d7605b47efb08dc370f6d0a71884cba944 # for v1.8.0

Credits

This action is based on the deprecated peter-evans/link-checker and uses lychee (written in Rust) instead of liche (written in Go) for link checking.

License

lychee is licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE)
• MIT License (LICENSE-MIT)

at your option.