Simply extend a shortened URL to its real URL by right clicking it and selecting 'Simple URL Extender'.
This was a very useful extension, but the service is now down. Check the ‘related’ tab for alternatives.
Only tested on a handful of short URLs so far. Works as expected and does not make any network requests. It does seem strangely slow to reveal a link, though.
Does exactly what it is supposed to, brilliant!
https://x.gd
https://openerurl.com
NewTabTodo
https://url-shortener.freebusinessapps.net