Firefox 42+: libgtk-3.so.0: cannot open shared object file: No such file or directory

Question

Asking, because it took a minute to figure this out and nothing came up on Google. Answer coming up.

I downloaded a Firefox (nightly) build from mozilla.org for testing. Running it presented an error:

$ firefox
XPCOMGlueLoad error for file /home/parallels/firefox-32/libmozgtk.so:
libgtk-3.so.0: cannot open shared object file: No such file or directory
Couldn't load XPCOM.

The file does exist on my Ubuntu 14.04 LTS:

$ locate libgtk-3.so.0
/usr/lib/x86_64-linux-gnu/libgtk-3.so.0
/usr/lib/x86_64-linux-gnu/libgtk-3.so.0.1000.8

Solution

Turns out I needed to download the x86_64 version from the Mozilla site, not the 32-bit version.

Comments

[zhihong]

Thanks for saving my time. I had the same problem when downgrade from firefox version 48 to 47 in ubuntu 14.04.