Mozilla take security very seriously and it’s also worth checking out the Mozilla Security Blog to see some of the work that goes into keeping Firefox safe. If you want to see just how many security threats have to be fixed on a regular basis by Mozilla, check out the latest Security Advisories for Firefox. Not only this, but you’ll also find that many add-ons or plugins simply won’t work with it anymore. We emphasize that using Firefox 16 is not a good idea because it is no longer updated or supported by Mozilla leaving it vulnerable to attack, malware, spyware and other online threats. Since Firefox 17 until the latest version of Firefox, you need at least OS X 10.6 Snow Leopard or higher to run the browser safely and efficiently on your Mac. In this article, we look at the risks and problems of using Firefox 16 and highlight what your options are. In this case you’ll need Firefox 3.6 for Mac which was the last one to support PPC Macs but is even older and more vulnerable than Firefox 16. Note that this only works if you’re using an Intel Mac – if you’re still using OS X 10.5 or 10.4 on a PowerPC Mac, then we recommend this article about how to install Firefox on PPC Macs and OS X 10.4.11.

However, we strongly recommend you upgrade to at least OS X 10.6 Snow Leopard or higher as Firefox 16 is no longer updated by Mozilla and therefore not secure anymore.

If you’re using OS X 10.5.8 Leopard then you can still download Firefox 16 for Macs which works on 10.5.8.

Firefox 45.0 osx