This extension has numerous accuracy concerns. For example, compare the result of 1/64 on this extension to what your phone says. If you're interested in a better experience, check out my extension: https://addons.mozilla.org/en-US/firefox/addon/address-bar-math/

I haven't added all the constants yet or the saved history but this is otherwise at feature parity and should function better for most use cases. Cheers!

It's really nice! The only thing is that I'm very lazy placing parentheses (especially for long equations). So 3+9)/4 for example instead of (3+9)/4 it would be nice if that would also work!

There's probably something I don't see, but I can't find how to actually use this extension. I'm typing simple math in the address bar (ex: "2+2") and I only see google results.
What am I missing?

Excellent one. Don't wait for crappy server connection if you don't have enough bandwidth. Keep up good work.

Simple and powerful, doesn't rely on external servers :)