Hi jpjcoughlan,

1. select the button "Always check if Firefox is your default Browser" at Options >> General >> Startup then close Firefox.
2. Open Firefox again
3. You should be promted to set Firefox as your default Browser.

hope I could help you

JustSecurity

Thanks for that. Yes that normally works but the problem since Avast updated and Edge updated, is the list of possible default browsers does not include Firefox when prompted to set as default. I have even tried the link "set defaults by app" and although this way lists firefox three times, clicking on any of the three simply brings up another link called "MANAGE" which does not appear to do anything.

https://support.mozilla.org/en-US/kb/how-make-web-links-open-firefox-default

https://support.mozilla.org/en-US/kb/setting-firefox-default-browser-does-not-work

https://support.mozilla.org/en-US/questions/1207775

https://support.mozilla.org/en-US/questions/1208759#answer-1086882

https://support.mozilla.org/en-US/kb/how-change-your-default-browser-windows-10

https://www.bing.com/search?q=change+default+browser+windows+10

Thanks for that Fred. The theory on the second link was worth the read. I got as far as the "set default by app" and was, like you , able to see three Firefoxes but had not thought of linking Firefox to HTTP. Doing that seems to have solved the problem. Until Microsoft update again!

Glad to help. Safe Surfing.