Can I run two different versions of Firefox at the same time?
If I can run two different versions of Firefox at the same time on one computer, how do I install the previous version?
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Hello
Index of /pub/firefox/releases https://ftp.mozilla.org/pub/firefox/releases/ Or Index of /pub/firefox/releases https://archive.mozilla.org/pub/firefox/releases/
Dedicated profiles per Firefox installation https://support.mozilla.org/en-US/kb/dedicated-profiles-firefox-installation Some users have multiple installations of Firefox, each in separate program folders. Firefox uses a dedicated profile for each installation of Firefox, including Nightly, Beta, Developer Edition and Extended Support Release (ESR) installations. This makes Firefox more stable when switching between installations on the same computer, and also allows you to run different Firefox installations at the same time.
Custom installation Firefox installation location choice and you will also have a new profile
Prerequisite to installation location, for example and Windows
64-bit Create Mozilla Firefox Release installation folder in C:\Program Files C:\Program Files\Mozilla Firefox Release Install Firefox in C:\Program Files\Mozilla Firefox Release
32-bit Create Mozilla Firefox Release installation folder in C:\Program Files (x86) C:\Program Files (x86)\Mozilla Firefox Release Install Firefox in C:\Program Files (x86)\Mozilla Firefox Release
Custom installation of Firefox on Windows https://support.mozilla.org/en-US/kb/custom-installation-firefox-on-windows
A Custom setup lets you choose the folder where Firefox program files will be installed
Other illustration https://connect.mozilla.org/t5/discussions/121-0-1-useless-quot-xyz-is-slowing-down-firefox-quot-links-stop/m-p/49414/highlight/true#M17683
You should use a separate, dedicated, profile for each version and use a desktop shortcut that specifies the profile (-P "profile_name"). You may have to use the -no-remote command-line parameter to be able to run multiple versions at the same time.
See "Creating a profile":
You can possibly use Sync to sync your personal data between the profiles.
You may want to install the 115 ESR version to a separate folder. Other older versions will immediately update to the latest version unless you apply the ManualAppUpdateOnly enterprise policy.