Starting with version 90, Firefox will automatically find and offer to use client authentication certificates provided by the operating system on macOS and Windows. This security and usability improvement has been available in Firefox since version 75, but previously end users had to manually enable it.
When a web browser negotiates a secure connection with a website, the web server sends a certificate to the browser to prove its identity. Some websites (most commonly corporate authentication systems) request that the browser sends a certificate back to it as well, so that the website visitor can prove their identity to the website (similar to logging in with a username and password). This is sometimes called “mutual authentication”.
Starting with Firefox version 90, when you connect to a website that requests a client authentication certificate, Firefox will automatically query the operating system for such certificates and give you the option to use one of them. This feature will be particularly beneficial when relying on a client certificate stored on a hardware token, since you do not have to import the certificate into Firefox or load a third-party module to communicate with the token on behalf of Firefox. No manual task or preconfiguration will be necessary when communicating with your corporate authentication system.
If you are a Firefox user, you don’t have to do anything to benefit from this usability and security improvement to load client certificates. As soon as your Firefox auto-updates to version 90, you can simply select your client certificate when prompted by a website. If you aren’t a Firefox user yet, you can download the latest version here to start benefiting from all the ways that Firefox works to protect you when browsing the web.