Are you trying to load a or run an old extension ?
Mozilla maintains an official archive of all old Firefox versions.
This version was designed to run smoothly on machines with limited RAM (such as 512MB to 1GB) and older processors like the Intel Pentium 4 or early Atom netbooks.
: Choose your operating system (e.g., /win32/ for Windows or /mac/ for older OS X). download old version of mozilla firefox 3.6
Firefox 3.6 was a significant upgrade from its predecessor (Firefox 3.5) and introduced several key features that were important at the time.
A Comprehensive Guide to Downloading and Using Older Versions of Mozilla Firefox (v3.6)
Mozilla maintains a public, historical archive often referred to as the "FTP server." You should never download legacy browsers from third-party file-sharing websites, as these files can easily be bundled with malware or adware. To download the genuine, unaltered software installer: Are you trying to load a or run an old extension
Firefox 3.6 requires Visual C++ 2008 Redistributables. Download the official Microsoft VC++ 2008 SP1 package separately, then re-run the Firefox installer.
For testing, legacy development, or specific compatibility needs, you can find the installers on the Mozilla FTP Archive :
Many older enterprise networks, industrial control panels, and academic databases were hardcoded to work exclusively with the rendering engines of IE 7/8 or Firefox 3.x. Modern security protocols often block these outdated portals entirely. Where to Safely Download Firefox 3.6 : Choose your operating system (e
What are you installing this on (Windows, Mac, or Linux)?
Firefox 3.6 is 13+ years old. It lacks modern security certificates (TLS 1.2/1.3), rendering most of the modern web (YouTube, Facebook, Reddit, Gmail) inaccessible or broken. Do not use this as your daily driver.
If you are successfully running Firefox 3.6, you will likely notice that the browser wants to update itself to the modern Firefox Quantum or ESR (Extended Support Release) editions. To freeze your browser at version 3.6, you must disable the auto-update feature immediately upon installation.