Inside the architecture folder, locate your language locale. For US English, select the folder. For UK English, select en-GB . Inside this final directory, click the executable file (e.g., Firefox Setup 52.9.0esr.exe ) to download the installer. Critical Post-Installation Steps
Modern Firefox profiles are often incompatible with older versions. If you plan to run an old version alongside a new one, it is highly recommended to create a separate profile Automatic Updates: Download Firefox 12-51 52 Esr
because they do not contain modern patches for web vulnerabilities. Mozilla Support Disable Auto-Updates: After installing, immediately go to Options/Preferences > General > Firefox Updates and set it to "Check for updates but let you choose to install them" "Never check for updates" to prevent it from jumping to a modern version. Separate Profiles: dedicated profile Inside the architecture folder, locate your language locale
Initiated the slow rollout of multi-process architecture (e.g10s), separating web content processing from the main browser interface to improve stability. Inside this final directory, click the executable file (e
Mozilla officially maintains an FTP server at archive.mozilla.org . This is the safest source (No viruses, no fake installers).