The option is up to you. The Developer had not updated Rank Checker in 6yrs. You can google for a replacement SEO from his page search box https://addons.mozilla.org/en-US/firefox/addon/nosquint/ Put SEO in. You will have to sift through the results for compatibility. info : How about looking at these 2 URL's first : https://www.howtogeek.com/333110/how-to-customize-firefox-quantum-and-remove-the-white-space-around-the-title-bar/ and The name is not descriptive enough : https://www.howtogeek.com/332449/whats-new-in-firefox-quantum/ More information will come out slowly. New extensions are being made and some older ones being updated Maybe something being updated here as is being tracked : http://bit.ly/2j0Anlj Going back : unfortunately 56.0.2 is no longer safe to use for every day use, but 52.5.0 ESR is! It will continue to get security updates until May 2018, and you can download and install it from this page: https://www.mozilla.org/en-US/firefox/organizations/all/ <b>Note : Legacy Extensions will be deleted or removed in any version update after May 2018.</b> You should make a backup of your Profile before going back and just because: https://support.mozilla.org/en-US/kb/back-and-restore- Please let us know if this solved your issue or if need further assistance.