Mozilla Firefox 9 is a web browser developed by Mozilla Foundation , available for download in full install version for Windows platforms from legacy sources. This version of Firefox was officially released on 2011-12-20 for public access and a brief summary of important updates and change log pertaining to this edition can be read below.

Firefox 9 is released with known issues some of them common to all platforms and few errors are platform specific.

For Windows users Adobe Reader X display random errors when PDF files are read within browser window. ALPS touch pad scrolling issues found while navigating vertically.

Bugs in Mac Platform includes add-ons settings incorrect in Firefox, Crashing of browser while file-chooser dialog opens, inability to use gestures for navigation, and can not run Firefox with Power PC CPU. In the Linux editions Quick Time video buttons do not work.