Mozilla Firefox 91 brings support for Windows single sign-on

Firefox Logo Horizontal Lockup 4
Firefox Logo Horizontal Lockup 4 (Image credit: Mozilla)

What you need to know

  • Mozilla recently released Firefox version 91.
  • Firefox 91 includes support for Windows single sign-on, making it easier to sign in to Microsoft accounts on the web.
  • The latest version of the browser also has over 1,200 bug fixes and a handful of other new features.

Mozilla released Firefox version 91 this week. The latest version of the browser has over 1,200 bug fixes and a handful of new features compared to its predecessor. Among its new features is support for Windows single sign-on (SSO). This feature lets you log in to Microsoft work and school accounts with credentials from your PC.

The update also adds a "more comprehensive logic for clearing cookies," according to Mozilla. This prevents hidden data leaks.

Here's what's new, as outlined by Mozilla:

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  • Building on Total Cookie Protection, we've added a more comprehensive logic for clearing cookies that prevents hidden data leaks and makes it easy for users to understand which websites are storing local information. Learn more
  • Firefox now supports logging into Microsoft, work, and school accounts using Windows single sign-on. Learn more
  • The simplify page when printing feature is back! When printing, under More settings > Format select the Simplified option when available to get a clutter-free page. Learn more
  • HTTPS-First Policy: Firefox Private Browsing windows now attempt to make all connections to websites secure, and fall back to insecure connections only when websites do not support it. Learn more
  • We've added a new locale: Scots (sco)
  • The address bar now provides Switch to Tab results also in Private Browsing windows.
  • Firefox now automatically enables High Contrast Mode when "Increase Contrast" is checked on MacOS
  • Firefox now does catch-up paints for almost all user interactions, enabling a 10-20% improvement in response time to most user interactions.

Firefox 91 performs catch-up paints for "almost all user interactions," according to Mozilla. The company explains that this results in a 10-20% improvement in response time for most interactions.

Sean Endicott
News Writer

Sean Endicott is a News Writer at Windows Central, where he covers Windows 11, Surface hardware, Microsoft 365, AI, apps, and the broader PC ecosystem. Since joining the site in 2017, he has written well over a thousand articles across the Microsoft landscape, covering breaking news, analysis, and feature reporting.

He writes Windows Wrap, a weekly column covering the biggest stories in Windows and the PC industry, and what they mean for the platform going forward.

Before joining Windows Central full-time, Sean worked in journalism and media production after earning a First Class degree in Broadcast Journalism from Nottingham Trent University. Outside of tech, he is an award-winning American football coach based in Nottingham, England, and was named BAFCA Youth Coach of the Year in 2024.