1. Go to a new tab, type in
about:config hit enter
2. Click the “I’ll be careful, I promise!” button
3. search for “
browser.gesture.pinch.in” right click on it and hit modify
4. A drop down that says “Enter string value” appears type in
cmd_fullZoomReduce
5. Click ok
Find the other ones and do the same. After you have entered all four you should see them in bold and on the right under value you should see only this cmd_fullZoomReduce part.
6.Once you have it all entered just close the tab and it should work.
I didn’t have to quit Firefox for it to work, but you may.
I’m using a MacBook Pro and it worked great, Hope this helps.
Preference Name / Value
browser.gesture.pinch.in / cmd_fullZoomReduce
browser.gesture.pinch.in.shift / cmd_fullZoomReset
browser.gesture.pinch.out / cmd_fullZoomEnlarge
browser.gesture.pinch.out.shift / cmd_fullZoomReset