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Why is Firefox 3.6.6 so slow?

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I have another kind of problem with Firefox


Firefox 3.6.6 is running REALLY slow.

Firefox just updated (automatically - I seemed to have no choice) to 3.6.6 on my Mac (OS 10.5.4) and is now running unbearably slow. Every website I try to load shows, at the bottom left "waiting for" (then website name) and loads very slowly, compared to Safari 3.1.2. I tried clearing the cache but that didn't help.

Even when on Firefox's own Mozilla support pages, it loads really slow.

What gives? Why did Firefox automatically update to something worse? Can I go backwards and reload the previous, faster version?

Firefox version


Operating system

Mac OS 10.5.4

Plugins installed


All Replies (20)

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A few days ago, I upgraded to Firefox 3.6.6. I never had any real problems with Firefox, except some expectable crashes due to use of a lot of memory and plug-ins (various tab pages with videos, chats etc.)

But now I encountered the same problem: Firefox takes 15 minutes (!) to start up and connect to any website, making it prohibitively slow. Starting up in Firefox safe mode doesn't make any difference. Firefox also uses excessive amounts of memory (up to 350 MB) when just accessing 'lo-fi' web pages, and the process often keeps running (and using this excessive memory) when I've closed Firefox.

I'm on Windows XP, Service Pack 3, 512 MB memory. I always clear my cache, defragment my disks, delete long browsing histories, repair my registry, run virus checks etc.

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firefox manual proxy configuration was found to be changed/set to spammers IP address.

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> firefox manual proxy configuration was found to be changed/set to spammers IP address.

That is amazing! What a weird coincidence. I would never have guessed that my upgrade must have coincided with being infected by a spammer. You must have concluded that from the sender details of my post? Great work, thanks a lot. And no complaints about Firefox after all.

So, setting the Firefox connection to 'No proxy' is enough to deal with this issue?


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each time I or another user tries to open a secure web site the message :Oracle Access Manager Operation has failed." Then instructs me to notify my administrator to solve this problem. I am the administrator. How do I solve this problem?

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Version 3.6.6 was not an upgrade, but a downgrade!! It just made things much worse!!! Until they fix this problem, Firefox is now utterly useless to me. The heart of the problem is the Plug-in Container together with the flash plug-in. The Plug-in container was just a bad idea from the get go. I wish I could just go back to an older version from back before this Plug-in Container was added in. If I had known that this supposed upgrade was in reality a downgrade, I would never have installed it.

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I'm running XP SP3. I mistakenly accepted the autoupgrade to 3.6.6. Compared to 3.6.4, running 3.6.6 is like trying to jog on a treadmill underwater.

I recently installed the "SearchTweaker" extension (, and noticed that all Google services (Google Maps, GMail, Google Reader, etc.) were locking Firefox up. I thought it was that, but using Bing maps was the same.

When going to any javascript page, Firefox locks up, for between 45 and 90 seconds, and takes much of my PC with it. Forget using video. I disabled Flash, and lo and behold, my PC can breath again.

I think I'll switch back to Opera and wait until Firefox decides to de-cripple their browser. Or maybe someone can make an uninstall to revert back to the working version?

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Same issue on XP, plugin-container and firefox taking my cpu to 100%. Also, I can no longer view PHP pages in firefox. Only changes I made was upgraded to newest firefox. I have no issues with Safari or Chrome.

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After my Firefox updated to 3.6.6 any web page that had Flash on it would behave very slowly. I narrowed the problem down to a setting in my F-Secure Internet Security called Deepguard. Turning it off made Firefox run normally again.

If anybody is using F-secure too then maybe give it a try.

Hope this helps

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I am unable to access certain websites anymore, they are just hang at loading. For example I open Internet Explorer and they open up immediately. This only started happening after the 3.6.6 update.

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Since the 3.6.6 update, logging out of Gmail or attempting to open any link within Gmail (Google documents, etc) freezes Firefox 100% of the time with my home machine.

Work machine doesn't have these issues, although it's on 3.6.6 as well. Very odd.

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Same thing. OS 10.4.11

Everything was running fine until this latest update. Now, I click on a site bookmarked on my toolbar, and Firefox just sits there, saying it's connecting, but not doing so.

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Mozilla automatically updated my Firefox and screwed up several things for me in the process.

Firefox is running extremely slow, I keep getting "Unresponsive script" warnings, photos look distorted, and I can no longer use my Ask & Record Toolbar which really ticks me off.

I'm sick of Firefox updating in ways that render my plug-ins useless!

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I had the same problem with FF 3.6.4, apparently Mozilla added a new feature called "plugin-container.exe" that prevents FF from crashing if, for example, Adobe Flash Player crashes, and you can simply refresh the page to restart the plugin, but this new feature had problems, it made the browser extremely slow, because FF 3.6.4 terminates the unresponsive plugin after waiting 10 seconds, and this had problems with older computers, and so I downgraded back to FF 3.6.3.

Once Mozilla released FF 3.6.6, I tried it, and the performance was better than FF 3.6.4, because FF 3.6.6 terminates the unresponsive plugin after waiting 45 seconds, but still the video on YouTube lags, which is caused by "plugin-container.exe" using so much memory, and so I downgraded back to FF 3.6.3 again...

If Mozilla wants to use "plugin-container.exe" on future FFs, which I fully support because the feature is actually neat, then Mozilla has to improve the "plugin-container.exe" so it won't slow down the browser and make the video on YouTube lag, particularly in older computer...

Mozilla cannot expect people to upgrade to newer computers, because of the prize tag...

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Same problem here. FF super slow since upgrade to 3.6.6. Other browsers work with usual (fast) speed.

@FF/Mozilla-Team: Thank you guys in advance for fixing this soon :-)

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Try temporary disabling your security software, i.e your anti-virus or any browsing protection.

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At least I'm not alone.Since upgrading to Firefox 3.6.4 the browser takes one minute to load and web pages even longer.My operating system is Vista.All plug ins disabled.I installed Google chrome and it is super fast but I did like Firefox before and would like it back.Surely Mozilla know there is a problem.LET US KNOW.

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anyone have a link to the old version 3.5.4 thats not beta? this slow down in performance is not acceptable! flickr and youtube runs like slow motion and memory usage is off the scale. 1.2gb memory used by firefox damn!

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vista64 user with the same problem. memory usage on startup is 750mb and can go up to 2gb with flash. prior to this update firefox was only using 200mb with flash. its definitely a firefox problem.

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On a windows 2000 sp4 650 MHz machine nothing is really fast, but the change to firefox 3.6.6 is totally catastrophic - even opening the "help->about firefox" dialog to re-check the version number was slow - took about 30 seconds to paint the elements of the window. Typing into this dialog box is so slow I have to pause periodically.


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