I installed this extension mainly to get "per website" desktop mode on Firefox for Android, for websites that dont show needed options in "mobile" view. I set the desktop user agent to be used on those domains + subdomains, via "custom" option (Google to get search tools, wikipedia for full user menu, etc). It works wonderfully and without issues, and it's clear it will completely revolutionise my mobile browsing. Wanted this for ages. Thank you - and you might want to mention this use in the description if it's useful to others. **Update/suggestion - allow a 2nd kind of custom list, for regex site matches, so one can apply the same user agent to multiple/similar sites, or to a regex site match, without need to re-enter the agent numerous times or update when the list of sites changes, because the regex will capture it. Make it a new category (wnd type of "custom list") so those not used to regex aren't frustrated by syntax => keeps the existing "simple" custom version working as-is for everyone.