Abbrefy
A completely free and powerful URL Shortener built with Python and Flask and embedded with advanced functionalities like URL customization, Links management, Actionable Analytics, and even Public SDKs and API integration for developers.
Contributing
Abbrefy is open source and very much open to contributions from others. Contribution can come either by improving the codebase (there's definitely a lot to be improved), adding new features, helping with fees to keep the service running, forking the project, or even dropping a star to help improve popularity.
If you wish to contribute code, please feel free to open a PR as well as an issue to reference your development.