Mozilla officially released Firefox 66 released, go and download and check what’s new. The new Firefox version is out there to fix autoplaying videos annoyance in websites and supports Windows Hello on Windows 10. Mozilla Firefox received web authentication support in version 60, but for Mozilla, Windows 10 is the first platform to support new FIDO 2 passwordless capabilites for web authentication.
Mozilla has confirmed in a blog post they’re planning to add Windows Hello support to Firefox ESR in middle of May, 2019 with ESR 60.0.7. If you’re using older versions of Windows, on them, Web Authentication will use Rust Hid library for interacting with U2F security keys.
Test Windows Hello in Firefox 66 on Windows 10
But sadly, you need to be using Windows 10 April 2019 Update version 1903, not Windows 10 April 2019 Update to test Windows Hello, which could be available next month. Or you can join Windows insider Program and install latest build from Fast ring, then you can try Hello in the below demo sites.