Need to spoof a referer for something, and out of the six extensions I've tried this is the only one that works properly/at all.

Taking one star off for user-unfriendliness; rules can't be modified after set, they have to be scrapped and redone.

It actually cannot modify the User-Agent header, if "Modify" selected. Had to click "Add" instead.

Works well, but minus 1-star for the lack of ability to edit a rule or even copy/paste the existing fields.

Would be great if there was an option to export and import headers so we can sync them between different Firefox installs.