GitHub Style Override is a tiny Chrome extension developed by union.io. It allows users to customize the appearance of GitHub.com by reverting the sans-serif font back to Helvetica. This change was made by GitHub in July of 2016, but if you prefer the older font style, this extension is perfect for you.

In addition to font customization, GitHub Style Override also includes a useful feature for code view. It allows users to set the number of spaces for tabs in GitHub's code view. By default, GitHub sets tabs to 8 spaces, but with this extension, you can set it to any number you prefer. The default value is 4, which provides a more concise and visually appealing code view.

Please note that this extension is only compatible with Mac devices. If you're looking to personalize your GitHub experience and have a Mac, give GitHub Style Override a try.