Primer is the CSS toolkit that powers GitHub’s front-end design. It’s purposefully limited to common components to provide our developers with the most flexibility, and to keep GitHub uniquely GitHubby. It’s built with SCSS and available via Bower, so it’s easy to include all or part of it within your own project.

Read the Primer documentation to learn more.

Heads up! We love open source, but Primer is unlikely to add new features that are not used in It’s first and foremost our CSS toolkit. We really love to share though, so hopefully that means we’re still friends <3.




Download the latest release and copy the SCSS files over to your own project. Once your files are in place, jump to the usage guidelines for including Primer into your own CSS.


$ bower install primer-css --save

Things to know

Hey, GitHubbers! For, run bower install at root. Be sure to commit and push all the changes, including the bower.json and everything under bower_components.


Once included, simply @import either the master SCSS file, or the individual files as you need them.

// Example: All of Primer
@import "primer-css/scss/primer";

// Example: Individual files
@import "primer-css/scss/variables";
@import "primer-css/scss/mixins";
@import "primer-css/scss/base";


Primer’s documentation is built with Jekyll and published to via the gh-pages branch.


You’ll need the following installed:

Chances are you have all this already if you work on github/github or similar projects. If you have all those set up, now you can install the dependencies:

$ npm install
$ bower install

Running locally

From the Terminal, start a local Jekyll server:

$ jekyll serve

Open a second Terminal tab to automatically recompile the Sass files, run autoprefixer, and update our Primer stats file:

$ grunt watch

Alternatively, you can manually run grunt and jekyll serve when needed.


Use the included Grunt task to generate and publish Primer’s docs to the gh-pages branch.

$ grunt publish

This takes the _site directory, generates it’s own Git repository there, and publishes the contents to the gh-pages branch here on GitHub. Changes are reflected in the hosted docs within a minute or so.

Primer stats

When compiling or watching the Sass files, Primer will automatically generate a file. This is tracked in the Git repository to provide us historical and contextual information on the changes we introduce. For example, we’ll know when the number of selectors or declarations rises sharply within a single change.


Within bower.json, update to a new release by changing the version number that follows the # in the dependency URL.

  "name": "myapp",
  "dependencies": {
    "primer-css": "x.x.x"

To pull down the updated package, cd into vendor/assets, and run bower install.

$ cd vendor/assets
$ bower install

Check in bower.json and all changes under vendor/assets/bower_components.


Development of Primer happens in our primary branch, master. For stable versions, see the releases page. master will always be up to date with the latest changes, including those which have yet to be released.


By contributing to Primer, you agree to the terms presented in this license agreement. More information will be provided here soon.

When contributing changes to Primer, be sure to do the following steps when opening a pull request:

  1. Bump the version number in bower.json (it’s purely placebo right now, but it’s good habit) and package.json.
  2. Run grunt and commit the changes. This compiles the SCSS to CSS so we can do basic analysis on the number of selectors, file size, etc.

In addition, please read through our contributing guidelines. Included are directions for opening issues, coding standards, and notes on development.

All HTML and CSS should conform to the style guidelines.

Editor preferences are available in the editor config for easy use in common text editors. Read more and download plugins at


For transparency into our release cycle and in striving to maintain backward compatibility, Primer is maintained under the Semantic Versioning guidelines. Sometimes we screw up, but we’ll adhere to those rules whenever possible.


Created by and copyright GitHub, Inc. Released under the MIT license.