Run the browser inside a virtual machine or a sandbox environment like Sandboxie to prevent any exploits from reaching your main operating system.
Open your current web browser (Chrome, Edge, or modern Firefox) and go to:
: To prevent the installer from automatically trying to download the newest version, it is often safer to run the installer while offline. download old version of mozilla firefox 3.6
Mozilla maintains an FTP archive of all their past releases. This is the safest source, as the files are original and have not been tampered with by third parties.
Despite the risks, there are valid use cases for this legacy browser: Run the browser inside a virtual machine or
Warning: Firefox 3.6 is an extremely old browser (released in 2010). It lacks modern security fixes, web standards support, and compatibility with most websites and extensions. Only use it for legacy testing on an isolated machine or virtual environment disconnected from sensitive accounts and data.
To prevent Firefox 3.6 from interfering with your current, modern Firefox installation, follow these isolation steps. Step 1: Disconnect from the Internet This is the safest source, as the files
On Windows 10, you might see: "The application has failed to start because its side-by-side configuration is incorrect."