GitHub reactions minimap is a Chrome extension developed by chrismwendt. It falls under the category of Browsers, specifically Add-ons & Tools. This extension enhances the GitHub experience by displaying reactions as red/green marks in the scrollbar.

The main feature of GitHub reactions minimap is the addition of marks to the scrollbar, which indicate the reactions on GitHub issues and PRs. These marks are colored based on the karma, which represents the difference between +1s and -1s. This visual representation allows users to quickly gauge the overall sentiment towards an issue or pull request.

With GitHub reactions minimap, users can easily navigate through GitHub repositories and get a sense of the community's response to various issues and PRs. This extension provides a convenient way to stay informed and make informed decisions.