r3dfox is a fork of the open source web browser Mozilla Firefox made specifically for Windows Vista, 7, and 8 compatibility. There may be other tweaks, however the goal is to remain as close to stock Firefox as possible.
Limited compatibility with One Core API on Windows XP is offered at the current time, however this is not tested consistently. Any issues that may arise that are hard to diagnose may be left to the extended kernel provider to fix.
An explanation of the Firefox Source Code Directory Structure and links to project pages with documentation can be found at:
https://firefox-source-docs.mozilla.org/contributing/directory_structure.html
For information on how to build Firefox from the source code and create the patch see:
https://firefox-source-docs.mozilla.org/contributing/contribution_quickref.html
If you have a question about developing Firefox, and can't find the solution
on https://firefox-source-docs.mozilla.org/, you can try asking your question on Matrix at chat.mozilla.org in Introduction (https://chat.mozilla.org/#/room/#introduction:mozilla.org) channel.
Nightly development builds can be downloaded from:
https://archive.mozilla.org/pub/firefox/nightly/latest-mozilla-central/
- or -
https://www.mozilla.org/firefox/channel/desktop/#nightly
Keep in mind that nightly builds, which are used by Firefox developers for testing, may be buggy.