Swiftfox is based on Firefox. It is available for GNU/Linux platforms and distributed by Jason Halme. Swiftfox is a set of builds of Firefox optimized for different Intel and AMD microprocessors. It is freely downloadable with open source code and proprietary binaries. Firefox extensions and plugins are compatible with Swiftfox, with notable exceptions. The name Swiftfox comes from the animal Swift Fox. Swiftfox differs from Firefox by a limited number of changes, and builds for different processors.
There is now an installer available that is distro independent. It is a script that downloads and installs Swiftfox in the /opt directory and attempts to use existing Firefox plugins. The installer is probably the best way for most users to install Swiftfox. If your distro is Debian based you will want to install using the deb files as the apt repository will provide automatic updating. More info is available at the deb file page.