If you are running an older operating system (like Windows 7 or older Linux distributions) that cannot support the newest Firefox, the archive lets you find the last compatible version.
For advanced users looking for specific Firefox for Android (Fenix) APKs, these are hosted at ftp.mozilla.org/pub/fenix/. Why Use the FTP Archive? download firefox ftp
While Firefox no longer supports browsing FTP sites natively, Mozilla still maintains a comprehensive FTP server as the primary archive for every version of Firefox ever released. Whether you are looking for the latest build or an obscure legacy version for testing, you can still by accessing their web-based archive. How to Access the Firefox FTP Server If you are running an older operating system