Bugzilla is one example of a class of programs called "Defect Tracking Systems", or, more commonly, "Bug-Tracking Systems". Defect Tracking Systems allow individual or groups of developers to keep track of outstanding bugs in their product effectively. Bugzilla was originally written by Terry Weissman in a programming language called "TCL", to replace a crappy bug-tracking database used internally for Netscape Communications. Terry later ported Bugzilla to Perl from TCL, and in Perl it remains to this day. Most commercial defect-tracking software vendors at the time charged enormous licensing fees, and Bugzilla quickly became a favorite of the open-source crowd (with its genesis in the open-source browser project, Mozilla). It is now the de-facto standard defect-tracking system against which all others are measured.

Bugzilla has matured immensely, and now boasts many advanced features. These include:

- integrated, product-based granular security schema
- inter-bug dependencies and dependency graphing
- advanced reporting capabilities
- a robust, stable RDBMS back-end
- extensive configurability
- a very well-understood and well-thought-out natural bug resolution protocol
- email, XML, console, and HTTP APIs
- available integration with automated software configuration management systems, including Perforce and CVS (through the Bugzilla email interface and checkin/checkout scripts)