Tap here to go to the mobile version of the site.
Your Firefox is out of date and may contain a security risk! Upgrade Firefox

Support Forum

Firefox 4 won't start on Mac OS X 10.4.11.


I get an error message from Firefox 4, saying it won't run on this level of operating system.

CPU 2 GHz Intel Core 2 Duo.

I had to go back to 3.16

Additional System Details

This happened

Every time Firefox opened

Installed Plug-ins

  • 1.1.7
  • Gecko default plugin
  • Runs Java applets using the latest installed versions of Java. For more information: Java Embedding Plugin. Run version test: Java Information.
  • RealPlayer Plugin
  • iPhoto6
  • 4.0.60129.0
  • Shockwave Flash 10.2 r152
  • The QuickTime Plugin allows you to view a wide variety of multimedia content in web pages. For more information, visit the QuickTime Web site.


  • User Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.4; en-US; rv: Gecko/20110303 Firefox/3.6.15

More Information

  • Moderator
1041 solutions 8840 answers

Firefox 4 requires at least OS X 10.5

esb501 0 solutions 9 answers

I attempted to download Firefox 4 because Firefox said it was compatible with Mac OS 4. I have OS 10.4.11. In attempting to download the downloader stated that I had a higher level of Firefox in applications and was attempting to download a lowever version. It asked if I wanted to do that or cancel so I canceled. Why does Firefox say that version 4 is compaitble with OS 4 when it obviously is not. Or should I have downloaded the newer version I thought I was downloading even though Firefox said I was downloading a version older than 3.6.17. The whole experience is very confusing and probably wrong. What's the right answer?

  • Top 10 Contributor
  • Moderator
10761 solutions 96849 answers

Helpful Reply

Firefox 4 requires at least OS X 10.5 and an Intel Mac.

For an unofficial Firefox 4 compatible version that runs on Mac OS X 10.4.11 or Mac OS X 10.5.8 (PowerPC) you can look at:

Firefox 3.6.x (Mac OS X 10.4 and later) can be found here: