Swiftweasel is a build of Mozilla Firefox source code, which uses non-trademarked graphics and logos. It is optimized for several architectures, and is available for the Linux platform only.

Released under the terms of the Mozilla Public License, Swiftweasel is free and open source software. It is distinct from Swiftfox (another optimized version of Firefox) in that Swiftweasel is completely free and open source while Swiftfox's binaries are proprietary.

Swiftweasel is optimized using the following methods:

As of the 3.0.3 release, Swiftweasel has shifted its primary optimization from processor specific to P.G.O. P.G.O. stands for Profile-guided optimization. It is a two step building process. The application is compiled one time and then run to produce a profile. The profile is then used to guide a second compilation of the application. Some of the older optimizations are still used, but there are now only Intel and AMD versions of each build. It is released compiled in a tar.gz package. There are also separate installers for Ubuntu and Arch linux available through their communities.