Does what it says on the box 100% well.
Doesn't seem to work on the new Firefox Quantum, I hope that'll be fixed shortly?
Edit: Samsung Galaxy S3 - Android - Firefox Beta 5.0b3 - I am still asked to acknowledge cookies.
Edit2: Sorry, nm, it works fine on Firefox 57.0. Wasn't sure if that was supposed to be the new version, seems it is.