Swiftfox is an optimized build of Mozilla Firefox for Linux. It is available for different types of CPUs with varying instruction sets, such as 3DNow!, MMX, SSE, and SSE2. Most of the performance gains, though, are due to the removal of Pango, which increases rendering time. Swiftfox is available for the following CPUs: The source code for Swiftfox is available under the MPL 1.1, but the compiled binaries cannot be distributed by anyone but the creator's site, and any browsers based on the source code cannot be called "Swiftfox."