There's an 8 year old issue in Bugzilla for this.[1] The Firefox team has finally put some resources into fixing it, but progress has been slow. I'm not holding out much hope -- Chrome has had this feature for a long time and it's never worked quite as well as Safari's.

A Firefox multi-touch zoom extension also exists[2], but it's not smooth enough to be useful to me (admittedly, this is on my old and slow 12" Macbook).

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=688990 [2] https://github.com/haxiomic/firefox-multi-touch-zoom

Right, seems like most problems are related to the Mac version. Wouldn't know about that, never had any noticable issues on Linux.