Can't configure multible hosts/domains. I add the first rule, everything ist still fine. After i add the second rule and i left the focus from inputfield, now its seems like shuffling all data. In rule1 and rule2 are the same host/domain and/or all the Useragents are the same right now. Whats going wrong?

Perfect, 100 % function.
FreeBSD , access site bank in BRAZIL

Giving it five stars because it actually works in the new firefox versions. It's a bit awkward having to go to the addons page to make changes, be nice if there was a toolbar button for easy access but it seems as if web extensions are all doing this.

The addon itself does the job however. I particularly like being able to set unique agents for specific sites. This is coming in handy right for now for youtube since by using an IE11 string I'm automatically getting the old format back. I know this won't last but as long as it does I'll make use of it.

Cannot export/import user agent list from old "User Agent Switcher" add-on.
Cannot wipe out all existing user agents with a single click
UI looks confusing, far less comfortable than aforementioned add-on

Three stars because it does the job, but I'm still looking for a more user-friendly option.

Does what it sets out to do.

Works for me. I can add rules. So, this rules changed User-Agent headers.

The "Add" button doesn't work, cannot add rules.