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Firefox slow on my MAC.

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New User

Firefox slow on my MAC.

Firefox is suffering from seriously annoying lag spikes on my mac, while other browsers work perfect. The problem is the worst when watching Youtube video's or when typing (text only appears after 1-2 seconds when the spike happens.)

I've tried the about:config stuff, I used Speedyfox, googled for days but nothing seems to be working. What's worth trying? I love Firefox and I don't want to switch to another browser.

Could it be firefox plugin process? It seems to be eating a lot of RAM from times to times (I updated Java and Flash).

Thank you

6 REPLIES
Site Moderator

Re: Firefox slow on my MAC.

The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information. Note: This will cause you to lose any Extensions, Open websites, and some Preferences.

To Reset Firefox do the following:

  1. Go to Firefox > Help > Troubleshooting Information.
  2. Click the "Reset Firefox" button.
  3. Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
  4. Firefox will open with all factory defaults applied.


Further information can be found in the Refresh Firefox - reset add-ons and settings article.

Did this fix your problems? Please report back to us!

New User

Re: Firefox slow on my MAC.

Thank you for the reply, but will I lose my RSS feeds if I do this?

Site Moderator

Re: Firefox slow on my MAC.

No, you shouldn't lose them.

New User

Re: Firefox slow on my MAC.

This was happening to me, and was driving me crazy! I came across an old thread (now closed). Tried it, and no more spike lags every couple of seconds. I set mine to 3600000, restarted Firefox, and no more lags.

From tklaus: At least for me, the problem was the session saver. Increasing the session save interval as described here eliminated the pauses:

http://www.techmynd.com/firefox-freezes-for-a-moment-after-every-10-sec-fix/

Site Moderator

Re: Firefox slow on my MAC.

Hi gslrider

How large is your sessionstore.js file?


You can check for problems with the sessionstore.js and sessionstore.bak files in the Firefox profile folder that store session data.

Delete the sessionstore.js file and possible sessionstore-##.js files with a number and sessionstore.bak in the Firefox profile folder.

Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost and you will have to recreate them (make a note or bookmark them).

New User

Re: Firefox slow on my MAC.

I was only able to locate sessionstore.bak (45k). No sessionstore.js in the profile folder. I'm currently running OS X 10.6.8.