Mozilla Firefox is a free and open-source web browser developed by Mozilla Foundation and its subsidiary, Mozilla Corporation. Downgrading to an older version can cause loss of Firefox user data, as well as performance and security issues, but there are just times when doing so is necessary. Each new iteration of the browser always has an upgrade with security fixes.

As long as you have good security software on your device, you will be fine to downgrade the browser by one version to the last stable release.

Check your current Firefox version

First, you need to know which version is currently installed on the device.

Windows

• Click the three lines, select “Help” near the bottom.
• Click on “About Firefox.” This will bring up a box letting you know which iteration you are currently using.

Mac

• On the menu bar, click the Firefox menu and select About Firefox.
• The About Firefox window will appear. The version number is listed underneath the Firefox name.

With the version details at hand, head over to the Mozilla Support page for release versions. The most recent version prior to the current one will be listed.

Install Firefox Old Version

Windows

Download Firefox Old Version for Windows

1. Open this link, Firefox Old Versions in the web browser.
2. Scroll to the Version you are looking for and select it.
   You should now have different builds of Firefox, according to your operating system.
3. Choose the directory of Windows.
   You will also see two different architectures under Windows, 32-bit, and 64-bit.
4. Pick the one that suits your CPU architecture.
5. Choose your Language and region, e.g, choose en-US, to translate it into English US.

Select the “.exe file”, and let the download begin.

Uninstall Firefox from Windows

After the download gets done, first uninstall the current version.

• Go to the Control Panel > All control Panel Items > Programs and Features.
• Click on the add or remove programs.
• Scroll down to select Mozilla Firefox.

Press the “Uninstall” option that gets activated at the top of the listed installed programs.

Follow the instructions to uninstall it from the operating system.

Install Old Firefox version on Windows

After disconnecting from the internet, proceed to install the older version of Firefox that you just downloaded.

Once you have installed the older version, disable Firefox automatic updates. You can refer to the steps we have mentioned in the ‘Disable Firefox Automatic Updates’ section.

Mac

Download Firefox Old Version for Mac

1. Open this link, Firefox Old Versions in the web browser.
2. Scroll to the Version you are looking for and select it.
   You should now have different builds of Firefox, according to your operating system.
3. Choose the directory of Mac.
4. Open the directory and there will be several other directories inside for each language. en-US is for US English and so on. Select the language you want.
5. Download the .dmg file to your Mac.

Uninstall Firefox from Mac

After the download is completed, first uninstall the current version from your Mac.

• Open Finder.
• Click on the Applications directory.
• Scroll to find Firefox from the list and select it.
• Press Command + Delete to uninstall Firefox.

Install Old Firefox version on Mac

After disconnecting from the internet, proceed to install the older version of Firefox that you just downloaded.

Once you have installed the older version, disable Firefox automatic updates. You can refer to the steps we have mentioned in the ‘Disable Firefox Automatic Updates’ section.

Disable Firefox Automatic Updates

Here’s how to disable automatic updates on Firefox:

1. Click on the Menu button at the top right corner.
2. In the General section, scroll down till you find the Firefox Updates section.
3. In the Allow Firefox to section, select Check for updates but let you choose to install them option.

After the above changes, Firefox will NOT update to the latest version automatically.