Praticamente, non funziona. Non è un simulatore di device ma è soltanto un rimpicciolitore di schermo.

Outupdate
Chrome version better than this shit

proを購入したが、Firefoxには対応していない

complètement déstabilisé, défauts fonctionnels; installé sans mon avis, désir ardemment de m'en libérer, mais comment?

En Firefox la versión premium no funciona y el desarrollador no contesta al soporte

the following "error" appears in the console after installing the extension:
Error: An unexpected error occurred spoofer.js

Latest Firefox on Windows 10. Plugin does nothing (dropdown with icons only) and have RAM leakage

It contains google spyware, aka analytics, I would be using Chrome if I wanted that. It also contains a really annoying advertisement which cannot be dismissed unless you pay the developer. There are better alternatives, for instance, Firefox>More tools>Responsive design mode. To much hassle for some chrome around the web page.

Ne fonctionne pas , dommage

Generally find onboarding pages irksome, unless needed and expected. An unwelcome onboarding page appeared after installing. The page said how to install the extension that was already installed, but on Chrome!? Uninstalled immediately after. The uninstallation nag page was the icing on the cake of annoyance. Might try again, if less pestering in the future.