How to Fix: Make Firefox Faster; Enable Multi-Processor Support

Dennis Faas's picture

Infopackets Reader Jesse T. writes:

" Dear Dennis,

A friend of mine told me that the new version of Firefox is a lot faster, but requires special configuration changes in order to get the speed boost. Do you know what she is referring to? How can I make my Firefox faster? "

My response:

Your friend is correct - the latest edition of Mozilla Firefox (version 48) includes a major overhaul to allow for multi-processor support, though it may not be enabled by default on some systems. That is because some systems may use older add-ons that may interfere with the multi-processor support feature, and so it becomes disabled by default. The good news is that you can forcefully enable the multi-processor support; in doing so you should see a fairly substantial performance boost - though some of your add-ons may break.

I can tell you from my own experience that previous editions of Firefox (prior to 48) seemed to suffer from exceptionally poor performance, but this latest edition is MUCH better at handling heavy loads and high memory usage. I personally use two Firefox add-ons called Tab Groups, and Tab Groups Helper, which allow me to have parent tabs (categories) and children tabs. On my system, it's not uncommon for Firefox to launch 10 parent tabs and have 25+ websites ready and loaded in memory - as such, Firefox typically eats up 750 MB - 1,000 MB of memory. With that much memory to manage at once, Firefox can slow to a crawl because the CPU must process all of that information, then try and keep things tidy using garbage collection. However, that isn't so much a problem now with the multiprocessor support - described next.

What Firefox "Multi-processor Support" Means, and How it Works

In the pre-2005 era, consumer-based computers largely supported single-core processor configurations, which were capable of processing one task at a time. Since 2005, however, PC's have supported dual, quad, six, and eight-core (and more) CPU configurations. What this means is that the operating system can handle running more than one process (program) at a time, thereby reducing the time it takes to process multiple tasks.

Since Firefox 48 now supports multi-core systems, it means that it can now process multiple web pages at a time, and spread that load across multiple CPU cores. Previously it did not - it could only utilize a single core, even if you have a multi-core system. With multi-processor support, this means a major performance boost (but only if your CPU has multiple cores).

It's important to note that even if your computer is multi-core, not all programs support multi-core configurations. For example, the Windows operating system supports multi-core processing, but the majority of programs that you run on Windows do not take advantage of multi-core processing. In that case, Windows will still run multi-core and handle processing a single program on one core, all the while managing other tasks at the same time.

How to Fix: Make Firefox Faster; Enable Multi-Processor Support

In order to take advantage of the multi-core processor support in Firefox, the first thing you need to do is to ensure that you're using the latest edition. To do so, launch Firefox and click Help -> About; this will have Firefox check your version and/or download the latest edition.

Once you have the latest edition, it's time to check and optionally forcefully enable multi-processor support. As I mentioned previously, the multi-processor support feature may be disabled depending on your setup (it was for me) - you can check this by launching Firefox, then enter in "about:support" in the address bar; near the bottom, you should see a heading that says: "Multiprocess Windows", then look at the value next to it. If it says "0/1", then that means it's disabled.

To enable multi-processor, go to "about:config" in the address bar, then right click over any one of the headings below, then select New -> Boolean, then enter in "browser.tabs.remote.force-enable", and press enter. On the proceeding window, click on the "True" value, and click OK. Next, close Firefox and go to "about:support" in the address bar to see if "Multiprocess Windows" is enabled - it should be.

Next, close Firefox and reload it. From here on out Firefox should handle heavy loads a lot better. Please also keep in mind that if you had to force the multi-processor support, it may also break some of your add-ons. If that is the case, then you may want to look around for add-ons that provide similar functionality and which work under the new Firefox, and then drop the unsupported add-on.

Lastly, it's also important to note that the multi-processor support in Firefox is still in its early stages. That means there may still be bugs, and likely major performance gains still further down the road - though as I mentioned before, it already seems a lot better than previous editions.

Got a Computer Question or Problem? Ask Dennis!

I need more computer questions. If you have a computer question - or even a computer problem that needs fixing - please email me with your question so that I can write more articles like this one. I can't promise I'll respond to all the messages I receive (depending on the volume), but I'll do my best.

About the author: Dennis Faas is the owner and operator of With over 30 years of computing experience, Dennis' areas of expertise are a broad range and include PC hardware, Microsoft Windows, Linux, network administration, and virtualization. Dennis holds a Bachelors degree in Computer Science (1999) and has authored 6 books on the topics of MS Windows and PC Security. If you like the advice you received on this page, please up-vote / Like this page and share it with friends. For technical support inquiries, Dennis can be reached via Live chat online this site using the Zopim Chat service (currently located at the bottom left of the screen); optionally, you can contact Dennis through the website contact form.

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gbruce40_3626's picture

Hi Dennis, I tried your instructions and they seem to work, however in the about support, Multiprocess Windows I had "0/2 disabled" After following your instructions I have "1/1 (Enabled by user)".

I have an Intel i7 processor which, if I understand correctly, is a Quad processor with eight cores (I'm not sure how they get 8 cores in a quad core processor). So does "1/1 enabled by user" seem OK to you? I had expectations of "8/8 enabled". Perhaps I am a dreamer.

There is a mistake in your instructions which I found confusing.
"To enable multi-processor, go to "about:config" in the address bar, then right click over *and* of the headings and select New -> Boolean,". The and should of-course be any. At 75, I am so slow that it took me about 5 minutes to figure that out.

Thank you for another great fix, your website is a must have.

Dennis Faas's picture

I've corrected the line you referenced, which now reads: To enable multi-processor, go to "about:config" in the address bar, then right click over any one of the headings below, then select New -> Boolean, then enter in "browser.tabs.remote.force-enable", and press enter.

As for the meaning of the boolean setting, I am not sure why it would have been 0/2 for you, but what is most important is what it reads after that setting, which is what it will have listed in (brackets) - it should say: (Enabled by user).

Pj's picture

Mine shows "0/9". That '9' is the number of windows I have open. Anyway, I have not 'Enabled' this yet. I may wait it out. :D

- Pj


leeroy's picture

I had no problem following your instructions either way. Updated to Firefox 48, verified settings and made the new entry in about:config. Firefox slowed to a crawl with three tabs open; wouldn't even complete third tab. After a 3-finger-salute Firefox came up as I had left it, and when video played in 3rd tab it was choppy and out of sync from the audio. My PC is running Windows 10 and my processor is an AMD A10 Fortunately I had no problem going back into about:config and toggling my new entry to "false". Once again all is (relatively) well.
I always appreciate your guidance - followed your detailed instructions in setting up this Windows 10 laptop in keeping as much privacy as possible. This time however, I have had to reverse your advice. Just wanted to post this in case anyone else ends up in the same (slow) boat!

Navy vet's picture

I had problems as well. Firefox became slow to respond and many links that I clicked on did not open. Roboform became non operational.

wilsonk_7551's picture

I, too, am slow for the reason expressed in the first comment. Regardless, I got hung up the longer portion of the phrase "any one of the headings below" because I couldn't understand specifically which headings were "below" and where they are. Could you provide some further instruction and/or nuance? Thank you. is so useful and relevant!

Stuart Berg's picture

I just found out that this doesn't play well with the Firefox 48.0 current RoboForm add-on version That's a deal breaker for me until RoboForm is updated so it will work.

spiras's picture

RoboForm doesn't work well with this feature. So I just right-clicked the "browser.tabs.remote.force-enable" entry and select "Toggle", close and re-open FF, and RoboForm works well again, albeit without multi-processor support.

gar.suitor_4798's picture

I use "Fluff Busting Purity" (FBP) with Facebook.
WHen multi-core support is enabled, there appears to be issues with FBP, because with each new page or refresh, the "New User" FBP screen appears, and all of the custom settings for FBP are reset.
This apparently has been an issue with FBP for other reasons, because there is a section in the troubleshooting hints on the FBP website that addresses this kind of issue. The suggestions there don't fix the problem, only disabling the multi-core processor line in "About:Config" fixes it.
Perhaps there's a reason why this is disabled by default. It could be that the developers recognize that this isn't 'ready for prime-time,' yet.

LouisianaJoe's picture

I had to reset the change. LastPass would not connect to its server when it was set. Now that I reset it, it does.