XBT Tracker is a free and open-source BitTorrent tracker written in C++ by Olaf van der Spek. Because it is a "pure" tracker, it does not offer a frontend. The software is specifically designed to consume few resources, while maintaining a high level of performance. It listens on port 2710 by default. XBT Tracker uses MySQL, but it can also run without it.
The project was hosted at Sourceforge until it moved to Google Code in 2011. In 2015, source moved to GitHub.