Github Repository Size is a Firefox addon aimed at developers who frequently use GitHub. This tool enhances the user experience by displaying repository sizes directly in the summary band of GitHub pages. By leveraging the GitHub public API, it provides quick access to vital information, allowing developers to assess repository sizes efficiently. The addon is particularly beneficial for those managing multiple projects or evaluating potential dependencies.

Installation and usage are simple, as it integrates smoothly into the existing GitHub interface. Users can easily click on the size element to retrieve information for any public repository. However, when dealing with private repositories, a Personal Access Token is required for access. While the size displayed might not always be perfectly accurate due to GitHub's data management, it still serves as a useful tool for optimizing development workflows.