From the few tests I conducted, I see that this extension is doing what it is supposed to do well. Well done. Its font is large and readable, and the extension's UI adapts to the system theme. Last but not least, it doesn't request any special permissions.

I think everyone might need this extension at least once or twice in their lives, even if they don't know it. We are bound to run into websites that incorrectly detect our regional language (or worse, offer a poor translation). In some of these cases, editing URL tokens could help a lot. For example, in the case of Google, adding the "hl=en" to the URL (or modifying the "hl" parameter to "en") helps.

Very useful tool for debug GET arguments in URL, thanks for developing! Uncomfortable that typed data are lost when switching to other tab before clicking "Submit query", but seems this is Firefox limitation - it don't allow "pin" extension popup window for stay visible :( Or maybe we can store typed data between "popup opens" in some local storage?

very easy to use :)