You cannot easily run two different major versions of standard Firefox simultaneously on one operating system due to profile conflicts. If you have modern Firefox installed, the system will try to upgrade the old version or merge profiles, causing corruption.

Developed primarily by John T. Haller and hosted on PortableApps.com, Portable Firefox is a modified version of Mozilla Firefox designed to run entirely from a removable drive, such as a USB flash drive, an external hard drive, or even a cloud folder.

To use this tool ethically and safely, restrict it to these scenarios:

Released originally in March 2017, Firefox 52 (specifically the ) marks the end of an era for several key functionalities:

The most significant distinction of Firefox 52 is that it was the final Extended Support Release (ESR) based on the old Gecko engine architecture before the switch to the multi-process architecture (e10s) and the eventual removal of legacy add-ons.

While one could technically install the old Firefox 52 setup file on a computer, the Portable version offers distinct advantages for this specific use case.

52 — Portable Firefox

You cannot easily run two different major versions of standard Firefox simultaneously on one operating system due to profile conflicts. If you have modern Firefox installed, the system will try to upgrade the old version or merge profiles, causing corruption.

Developed primarily by John T. Haller and hosted on PortableApps.com, Portable Firefox is a modified version of Mozilla Firefox designed to run entirely from a removable drive, such as a USB flash drive, an external hard drive, or even a cloud folder.

To use this tool ethically and safely, restrict it to these scenarios:

Released originally in March 2017, Firefox 52 (specifically the ) marks the end of an era for several key functionalities:

The most significant distinction of Firefox 52 is that it was the final Extended Support Release (ESR) based on the old Gecko engine architecture before the switch to the multi-process architecture (e10s) and the eventual removal of legacy add-ons.

While one could technically install the old Firefox 52 setup file on a computer, the Portable version offers distinct advantages for this specific use case.