Firefox 100 on Windows 7 requires KB4474419 Update

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Beginning with Firefox 100, Windows 7 SP1 users must have the KB4474419 update installed prior to installation of the Firefox browser, otherwise, it may not work. This is because Mozilla has signed Firefox for Windows installer with an SHA-256 digest than SHA-1. Below you can check and verify do you have the mandatory security update installed, otherwise, we’ve covered the instructions on how to manually install the KB4474419 update.

Firefox 100

Some Windows Updates, especially Security updates are pretty mandatory. If users don’t install them on their device Windows may not work properly and you can’t install certain apps also. Such is the case with Firefox 100 release on legacy Windows OS.

Firefox version 100 need KB4474419 on Windows 7 for successfull installation

Back in 2019, Microsoft ditched SHA-1 and introduced SHA2- code signing support for Windows 7 SP1 and Windows Server 2008 R2 SP1, and Windows Server 2008 SP2 with KB4474419.

You may have the update automatically installed in October 2019, here is how to check.

  1. Open Control Panel
  2. Click on Programs > Programs and Features >
  3. Click on “View installed updates
  4. Search for KB4467719, if you’ve “Security update for Microsoft Windows (KB4474419)” listed, you don’t need to worry. Once you update to or install Firefox 100, it will work without any issues.
    KB4474419 update not listed in Windows 7 installed updates

If you don’t have the mandatory update installed, you may not be able to install Firefox. For instance, in the past, Kaspersky has thrown this error for lacking the update.

“The operating system does not support the SHA-2 as the signature algorithm. To install the application, you must install Windows Security update KB4474419”.

Firefox installer for Windows comes signed with SHA2-digest

“Beginning in this release, the Firefox installer for Windows is signed with an SHA-256 digest, rather than SHA-1. Update KB4474419 is required for successful installation on a computer running the Microsoft Windows 7 Operating system” Mozilla noted.

You can install this update on Windows 7 SP1 via Windows Update or from the Micorsoft update catalog.

How to install KB4474419 update manually

  1. Visit the Microsoft update catalog and look for the KB4474419 update for Windows 7
  2. Select the x86 or x64 version of the OS and click the download button
  3. Double click on .msu file, and the update will be downloaded. Run it once the download is complete to start the installation.
  4. After the update is installed, restart the computer.

How to install Firefox 100 on Windows 7

1. Once you have the KB4474419 update installed, visit this page

2. And, download Firefox browser and install it on Windows 7.

Firefox doesn’t support Windows Vista anyway.

This change doesn’t affect Firefox running on Windows 8, Windows 10, and Windows 11.

Firefox 100 is scheduled to release on May 03.

With the user agent string hitting a three-digit number, some websites may not work in this version

As of writing the article, we’ve been able to successfully install the beta and Nightly versions of the affected Firefox version on Windows 7 that doesn’t have Update installed without any issues.

Are you still using Firefox on Windows 7? Why haven’t you upgraded to Windows 10 or Windows 11? Let us know in the comments below.

More on Firefox:

Firefox 98 arriving today: here is what’s new, changed, and Fixed

Firefox Picture-in-Picture gets YouTube Subtitles and Captions Support

How to restore download Prompt in Firefox 98

Mozilla Firefox gets Windows 11 Style Scrollbars