I installed it just now and it worked immediately. I was looking for something that would reveal all alt text, such as with a hover popup, but for some reason no good options exist. This is close enough, because at least I can access the alt text using this copy option, then just paste it somewhere (like the address bar) so I can read it.

This extension, despite being 2 years old, works perfectly and does exactly what it says on the tin. No intrusive privacy violations, no donation requests, it just works. Thank you easrng!