In version 91 of Firefox, released on August 10th, Mozilla has reverse engineered the way Microsoft sets Edge as default in Windows 10, and enabled Firefox to quickly make itself the default. Before this change, Firefox users would be sent to the Settings part of Windows 10 to then have to select Firefox as a default browser and ignore Microsoft’s plea to keep Edge.
Mozilla’s reverse engineering means you can now set Firefox as the default from within the browser, and it does all the work in the background with no additional prompts. This circumvents Microsoft’s anti-hijacking protections that the company built into Windows 10 to ensure malware couldn’t hijack default apps. Microsoft tells us this is not supported in Windows.
Sadly, this does not work on Windows 11, where Microsoft is now forcing users to change the default handler for every individual file type a browser might use.