We run a pay-as-you-go proxy service. Until this month, using it in a browser meant the manual route: open the proxy settings, type a hostname and port, build a username by hand, sign in at the 407 prompt, and repeat the whole thing every time you wanted a different country. So we built an extension. One popup: product line, country, fixed or rotating IP, a "new IP" button, and an on/off toggle. It is live for Firefox and Microsoft Edge . The popup took an afternoon. The part worth writing...