Closed Bug 358773 Opened 13 years ago Closed 11 years ago

Firefox 2 runs 50 degrees F hotter than Safari or Firefox 1.5


(Firefox :: General, defect, major)

2.0 Branch
Not set





(Reporter: gkrodg00, Unassigned)


(Keywords: perf, Whiteboard: closeme 2009-01-20)

User-Agent:       Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en) AppleWebKit/418.9 (KHTML, like Gecko) Safari/419.3
Build Identifier: 

I am unsure if this is a bug or more just a symptom of memory leak. Firefox 2 nearly immediately causes a 50 degree increase in temperature on the Macbook. I had been plagued by the random shutdowns that Apple recently released a firmware update to address this. 4 days later and no shutdowns. I have a temp monitor app running in the menubar and after upgrading to Firefox 2, Firefox is nearly unusable after about an hour of useage. It runs slow, it opens pages slow and the temp of the machine reaches 180-190 degrees. If run SMCFanControl wide open at 6200 RPM it still runs that hot. However, if I shut down Firefox, the temp plummets to 130-140 degrees using Safari. That is the range Firefox 1.5 operated at. If I run SMCFanControl, the temp will fall even further.  At first, I thought it was the new firmware from Apple, but the temp only goes that high with Firefox 2.

Reproducible: Always

Steps to Reproduce:
1. Use a temp monitor application in MacOSX 10.4 on Macbook
2. Launch Firefox 2
3. After about 1 minute, temp jumps to 180+ without surfing or any other applications open
4. Close Firefox 2 and about 1 minute later, drops back to 125-130 degree range.

I assume this is a memory leak problem or perhaps related to problems with the Macbook the are already well documented. Never encountered this with Firefox 1.5, but this happens everytime and without any other applications open in Firefox 2.
Reporter: Have you checked the coolant levels in your profile? Also make sure the radiator fins (sometimes called "tabs") are set to always be displayed, and that they are unobstructed by other windows floating on top. Check the coolant pump (sometimes called the "throbber" in the upper right corner) to make sure it's circulating the fluid properly.
If you run Activity Monitor (included with Mac OS X), do you see Firefox using close to 100% CPU?  If so, can you hit the "Sample Process" button (you might have to click "Inspect" fiirst) and find out what thread and function is using nearly 100% CPU?  If the sample isn't too big, you can attach it to the bug report using the "Create a new attachment" link.
Have you dismantled your MacBook to fix the thermal paste between the heatsink and the processor?  I know that one some of the first MacBooks they had serious issues with so much thermal paste being there that it would hold heat in instead of conducting it through which caused temps to be very high.  I don't think the upgrade is directly responsible for the temp increase, although it may be a symptom of temporary maxed CPU usage.
no, i haven't broken the computer down, but i have seen the reports of the thermal paste.

i apologize the video is a little grainy, but there are a few spots where the temp can be clearly seen. Also, the fan kicks in immediately. You can see from the video that the processor doesn't really peg out at 100%, more like a 45-50% load.

I switched back to Firefox 1.5 because it just wasn't usuable. The heat slowed the computer to a crawl. 

Firefox 2 DOES cause my macbook to run hot. it was reproducible EVERYTIME it was launched. i have switched back and that behavior is gone.
Version: unspecified → 1.5.0.x Branch
A bug report like this isn't much more useful than "Sometimes Firefox crashes" or "Once I saw Firefox use more than 500MB of RAM" or "Firefox always uses 100% CPU".  These are all things that could be caused by bugs in almost any part of Firefox.

To figure out what the bug is, we need a sample.

You might also have luck with
Reporter: can you try this with a clean profile? To do so, go to /Users/<yourusername>/Library/Application Support/Firefox/ and drag the Profiles folder to the desktop for the time being. This will reset all your settings. If the issue has gone away, you can try copying files from your old profile to the new one.

Speculating wildly, I'm guessing your profile got corrupted somehow and that is causing Firefox 2 to run at 100% CPU usage. 

Let us know if the clean profile fixed the issue.  
Does the CPU usage depend on what site you're on?  I noticed that in the video you posted, the site had several animations.  While I'd hope those wouldn't cause 40% CPU usage, maybe they do.
Keywords: perf
Hardware: Macintosh → PC
Version: 1.5.0.x Branch → 2.0 Branch
the video was from my home page,, but any site caused it too run hot. i just wanted to illustrate that doing absolutely no browsing created this situation. i ran firefox 2 for about 5 days and all sites caused the same problem.

i can appreciate your need for more information and system logs, etc. i have switched back to 1.5 as it is stable, functional & runs at a normal temp. all i did was re-install over firefox 2 and its fine, so i would think this eliminates the preferences.

i'll re-install firefox 2 and run the diagnostic you suggested over the weekend and report back. i really appreciate the support. i just thought i had found a problem and wanted to report it, but i hadn't seen it reported yet. at first, i assumed it was a macbook problem because i was hit by the random shutdowns, but no shutdowns for a week since the new firmware. i upgraded right after the new firmware so i thought at first the firware was causing the increased temp, but i found i could reproduce it everytime with only firefox 2 running. btw, i'm not trying to bash firefox, i love it and have been using it since spring of 2004 and have converted all my friends and family, but i'm not a programmer and don't have any real computer education. i'm an emergency physician. anyway, thanks for the suggestions, i'll report back over the weekend...g
A few more things to try. 

First of all, like Jesse points out, it's interesting to know if there's a difference between different sites. 

Try a clean, new profile (no extensions, please) and see if you get the exact same result by having "about:blank" as the start page, and some other site of your choice.

If you find something specific that makes the processor usage high, you can create a sample by following the instructions here:

The temperature of the processor is not Firefox as a client application can control (unless the CPU usage is abnormally high), so one could possibly also argue that this is a hardware/computer bug. MacBooks have had temperature problems many times in the past... 

Now you may say that "it works in Safari, so why not in Firefox?". Under the hood, Firefox 2 still uses Carbon and not Cocoa, which makes a significant difference to the system, as it is presumably optimized for Cocoa, which Safari (and other mac apps that don't have to care about backwards compatibility) can take advantage of.

Anyway, if you can find more specific factors/data that makes the computer hot, this bug may be useful, but in general comment 5 holds true. Bug reports in general need to be more specific, for us to have a realistic chance of fixing them.
I agree that If 50% CPU usage makes his computer dangerously hot, that's a problem with his computer.  But let's not focus too much on temperature; Firefox should not be using 50% CPU just displaying in the first place, and it would be good to know why it is using that much CPU.
What's the CPU in this particular MacBook?  If it's one of the Intel ones with Hyperthreading, then 50% CPU is equivalent to one thread using 100%.  (Which would be consistent with Jesse's initial suspicion.)
macbook is core duo 2.0 ghz, 2gb ram
do you see this problem when using firefox 3?
Whiteboard: closeme 2009-01-20
2+ years with no activity, old version, nebulous issue, closing.
Closed: 11 years ago
Resolution: --- → WORKSFORME
Firefox 2 is EOL'd and also this doesn't happen on my macbook in Firefox 3, verified WFM
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