Cross-browser testing is pretty essential when developing web sites. Most of the bugs you need to fix are probably in older versions of Internet Explorer. Both Chrome and Firefox have a very fast release cycle, where new versions are released every six weeks or so.

However, there are still many people using the older 3.6 version of Firefox. Firefox 3.6 has a few bugs, and because of its big installed base you probably need to run some tests on it as well.

There’s a problem here: Firefox doesn’t like it when two different versions are run side-by-side. Fortunately there are a few tricks you can use to make this happen. This should also work on Snow Leopard, provided you have at least 10.6.2, because the --args parameter was introduced in that version.

1. Download the Firefox 3.6 release from Mozilla.com.
2. Unzip and mount the DMG file.
3. Drag the file from the DMG to your Desktop instead of to the Applications folder.
4. Rename the .app to ‘Firefox36.app’ and move it to your /Applications folder
5. Run this command from a Terminal (found in /Applications/Utilities):
   /Applications/Firefox36.app/Contents/MacOS/firefox-bin -ProfileManager
6. Add a new account. Call it ‘test’.
7. Run Automator. From the ‘Choose a type for your document’ menu, select ‘Application’.
8. Drag ‘Run Shell Script’ to the action area.
9. In the content area (where ‘cat’ is displayed) copy-paste this line:
   open /Applications/Firefox36.app --args -P test
10. Save the document to /Applications as ‘Firefox 3.6’
11. Drag ‘Firefox 3.6’ application from the Applications folder to your dock for fast access.
12. You’re done!

For a nice icon to differentiate your current Firefox version with the old one get the full resolution PNG from above this article right here. Open it in preview, select all (Cmd-A) and press copy (Cmd-C). Open up the Automator .app by right-clicking and selecting ‘Get info’ or hitting Cmd-I. Select the icon in the topleft corner so that it is outlined and press Paste (Cmd-V).

Add a comment

7 comments

• JB 2011-08-25 on 03:28

  Hi, i’m afraid i can’t manage to make this work on OS Lion… but i’m a noob i’m afraid.

  The thing is it tells me that ther’s no such file or directory, after i pressed entry on the first line of code on terminal….

  I dl the file, unzipped it, dragged it on desktop, renamed it, put it in applications file…
  but the terminal won’t let me find it.

  I already have firefox 6 installed in the app files, should i uninstall it ? Or close firefox when running the terminal ?
  I think the problem has to be elsewhere…

  Could you help ? please.

• Danny 2011-08-29 on 19:32

  /Applications/Firefox36.app/Content/MacOS/firefox-bin -ProfileManager

  Should be

  /Applications/Firefox36.app/Contents/MacOS/firefox-bin -ProfileManager

  Content was missing an S

• Hay 2011-08-30 on 14:49

  Thanks Danny! I fixed it in the article.

• Thanos 2012-03-03 on 19:00

  Thanx a million. Works like a gem :)

• Karl 2012-03-23 on 11:13

  Thanks for this, very useful. As a fairly new user to a Mac the following may help others, I removed FF before I started as mounting means that you have to double click the icon to install FF3.6. If you don’t do this you get the folder not found error as described by JB above. After it is installed you can reinstall the current version.

• Chris Jacob 2012-10-15 on 00:04

  Thanks for this info – worked a treat.

  Suggestion:

  Once you have launched Firefox go to menu:
  Firefox -> Preferences -> Advanced -> Update … set “Never check for updates”

• very helpful 2018-10-17 on 13:34

  Thanks a lot, after hours of search, finally your solution helped.
  For the record, if some is new in mac and confused like me:
  Step 7: the OP is referring to an built-in application in Mac called “Automator”.