Markdown lint tool

A tool to check markdown files and flag style issues.

Installation

Markdownlint is written in ruby and is distributed as a rubygem. As long as you have a relatively up to date ruby on your system, markdownlint will be simple to install and use. You have 2 options to install it:

To install from rubygems, run:

gem install mdl

To install the latest development version from github:

git clone https://github.com/markdownlint/markdownlint
cd markdownlint
rake install

Note that you will need rake (gem install rake) and bundler (gem install bundler) in order to build from source.

Usage

To have markdownlint check your markdown files, simply run mdl with the filenames as a parameter:

mdl README.md

Markdownlint can also take a directory, and it will scan all markdown files within the directory (and nested directories):

mdl docs/

If you don't specify a filename, markdownlint will use stdin:

cat foo.md | mdl

Markdownlint will output a list of issues it finds, and the line number where the issue is. See RULES.md for information on each issue, as well as how to correct it:

README.md:1: MD013 Line length
README.md:70: MD029 Ordered list item prefix
README.md:71: MD029 Ordered list item prefix
README.md:72: MD029 Ordered list item prefix
README.md:73: MD029 Ordered list item prefix

Markdownlint has many more options you can pass on the command line, run mdl --help to see what they are, or see the documentation on configuring markdownlint.

Styles

Not everyone writes markdown in the same way, and there are multiple flavors and styles, each of which are valid. While markdownlint's default settings will result in markdown files that reflect the author's preferred markdown authoring preferences, your project may have different guidelines.

It's not markdownlint's intention to dictate any one specific style, and in order to support these differing styles and/or preferences, markdownlint supports what are called 'style files'. A style file is a file describing which rules markdownlint should enable, and also what settings to apply to individual rules. For example, rule MD013 checks for long lines, and by default will report an issue for any line longer than 80 characters. If your project has a different maximum line length limit, or if you don't want to enforce a line limit at all, then this can be configured in a style file.

For more information on creating style files, see the creating styles document.

Related projects

markdownlint and markdownlint-cli for Node.js

Contributing