Using the content linter

About the GitHub Docs content linter

Our content linter enforces style guide rules in our Markdown content.

The linter uses markdownlint as the framework to perform checks, report flaws, and automatically fix content, when possible. This framework flexibly runs specific rules, gives descriptive error messages, and fixes errors. The GitHub Docs content linter uses several existing markdownlint rules and additional custom rules to check the Markdown content in our content and data directories. Our custom rules implement checks that are either not yet available in the markdownlint framework or are specific to GitHub Docs content. Rules check the syntax for both Markdown and Liquid.

Running the GitHub Docs content linter

The GitHub Docs content linter will run automatically on pre-commit, but you can also run it manually.

Automatically run the linter on pre-commit

When you are writing content locally and committing files using the command line, those staged files will automatically be linted by the content linter. Both warnings and errors are reported, but only errors will prevent your commit from completing.

If any errors are reported, your commit will not complete. You will need to fix the reported errors, re-add the changed files, and commit your changes again. Any errors that are reported must be fixed to prevent introducing errors in the content that are in violation of the GitHub Docs style guide. If any warnings are reported, you can optionally choose to fix them or not.

When you are writing content locally, there are several rules that you can fix automatically using the command line. If you want to automatically fix errors that can be fixed, see Automatically fix errors that can be fixed.

If you are editing a file in the GitHub UI, you will not be able to automatically fix errors or run the linter on a commit, but you will get a CI failure if the content violates any rules with a severity of error.

Manually run the linter

Run the linter on staged and changed files

Use the following command to run the linter locally on your staged and changed files. It will output both warning and error severity flaws.

npm run lint-content

Run the linter on staged and changed files and only report errors

Use the following command to run the linter locally on your staged and changed files, and report only error severity flaws.

npm run lint-content -- --errors

Run the linter on specific files or directories

Use the following command to run the linter locally on specific files or directories. Separate multiple paths with a space. You can include both files and directories in the same command.

npm run lint-content -- \
  --paths content/FILENAME.md content/DIRECTORY

npm run lint-content -- \
  --paths content/FILENAME.md content/DIRECTORY

Automatically fix errors that can be fixed

If an error has fixable: true in its description, you can use the following commands to automatically fix them.

Run this command to fix staged and changed files only:

npm run lint-content -- --fix

Run this command to fix specific files or directories:

npm run lint-content -- \
  --fix --paths content/FILENAME.md content/DIRECTORY

Run a specific set of linter rules

Use the following command to run one or more specific linter rules. These examples run the heading-increment and code-fence-line-length rules. Replace heading-increment code-fence-line-length with one or more linter aliases that you would like to run. To see the list of linter rules you can pass to this option, run npm run lint-content -- --help. You can use either the short name (for example, MD001) or long name (for example, heading-increment) of a linter rule.

Run the specified linter rules on all staged and changed files:

npm run lint-content -- \
  --rules heading-increment code-fence-line-length

Run the specified linter rules on specific files or directories:

npm run lint-content -- \
  --rules heading-increment code-fence-line-length \
  --path content/FILENAME.md content/DIRECTORY

Bypass the commit hook

If the linter catches errors that you did not introduce, you can bypass the git commit hook by using the --no-verify option when you commit your changes.

git commit -m 'MESSAGE' --no-verify

Display the help menu for the content linter script

npm run lint-content -- --help

Linting rules

Each rule is configured in a file in src/content-linter/style, which is where the severities of rules are defined.

Errors must be addressed before merging your changes to the main branch. Warnings should be addressed but do not prevent a change from being merged into the main branch. Most rules will eventually be promoted to errors, once the content no longer has warning violations.