Firefox no longer works with Mac OS X 10.5
Firefox 16 is the last version of Firefox that works with Mac OS X 10.5 (Leopard) on an Intel-based Mac. To stay safe online, we recommend upgrading your computer or operating system. This article covers your options.
Option 1: Upgrade your operating system
Apple stopped supporting Mac OS X 10.5 in 2009 and many software makers have either dropped support for it or soon will. Newer versions of Firefox require Mac OS X 10.6 (Snow Leopard) or above. Depending on the age of your computer, you may be able to upgrade to a newer version of Mac OS X. If you can't upgrade to Mac OS X 10.8 (Mountain Lion), newer versions of Firefox will also work on Mac OS X 10.7 (Lion) and 10.6 (Snow Leopard). Apple still supports these older operating systems, although it's likely that it will drop support for 10.6 (Snow Leopard) soon.
Option 2: Switch to a newer computer
If your computer is not capable of running a newer version of Mac OS X then you will need to purchase a new computer to allow you to run the latest and greatest Firefox. You can transfer your settings across so you don't lose anything.
Option 3: Continue to use Mac OS X 10.5 and Firefox 16
If you can't switch to a newer computer or upgrade your operating system, you can continue to use Mac OS X 10.5 and Firefox 16. However, you will no longer receive stability and security updates available in upcoming Firefox versions. See the Security Advisories for Firefox for a list of vulnerabilities fixed in past releases.
If you need to reinstall Firefox 16 on your Intel Mac, you can download it from this link: