Firefox 54: multi-process gets another content process

Martin Brinkmann
Jan 26, 2017
Updated • Jan 26, 2017

The most recent Nightly version of the Firefox browser, Firefox Nightly 54, ships with two content processes instead of just one.

Firefox's multi-process architecture still rolls out to Firefox stable versions. That process will still take a couple of release cycles to reach all users of the stable version of the Firefox web browser.

Firefox uses a content process for all tabs open in the browser, and a separate process for the browser core.  Separating the core browser from the rest improves stability, and also responsiveness and other metrics of the browser.

If a tab crashes, there is less chance that it will take the whole browser with it doing so.

firefox multi process processes

Mozilla's implementation is different from how Google handles the multi-process architecture in Chrome. Chrome runs any open tab in its own content-process. The upside of this is that it improves stability and also security further. There is a downside to this however as well, as doing so requires more RAM.

Tip: Chrome users can save a bit of memory by configuring Chrome to use one process per site, opposed to one process per tab.

Back in 2016 I explained how Firefox Nightly users can increase the number of content processes that Firefox uses for its multi-process architecture. I enabled eight content processes on the machine back then and have not changed the value since.

I noticed a couple of issues, but nothing too major.

Mozilla has done the same now for the new Firefox 54 Nightly version. It pushed the content processes to two. This marks an important step in the whole multi-process architecture system of the browser.

Two content processes is the next big step, as it paves the way for enabling more than two content processes in the future. The number of content processes that Firefox will eventually ship with by default has not been decided on yet.

While that is done for testing primarily right now, it does mean that Mozilla thinks the implementation is stable enough as it enabled it for all Nightly users who upgrade or install Firefox 54.

The new multi-process setting will trickle down to Firefox Stable eventually, but a schedule for that has not been posted yet.

Mozilla will probably never mimic Chrome's one process per tab behavior. It would increase memory use by a lot. This is not a problem on modern systems with 8, 16 or even more Gigabytes of RAM, but the largest part of Firefox's user base uses machines with 4 Gigabytes of RAM or less.

Last metrics show more than 18% with 2 Gigabyte, more than 15% with 3 Gigabyte, and more than 5% with 1 Gigabyte of RAM. (via Sören Hentzschel)

Now You: if you use Firefox, is it multi-process already?

Firefox 54: multi-process gets another content process
Article Name
Firefox 54: multi-process gets another content process
The most recent Nightly version of the Firefox browser, Firefox Nightly 54, ships with two content processes instead of just one.
Ghacks Technology News

Tutorials & Tips

Previous Post: «
Next Post: «


  1. max said on November 17, 2017 at 12:44 pm

    I have enabled it manual when lookup why firebug stop work correctly

    it use more ram but still work fine;

  2. EuroScept1C said on January 26, 2017 at 6:07 pm

    I always use latest drivers for my motherboard, chipset, ME, GPU and Sound card. I don’t even remember when was the last time I got a Windows or Firefox crash. Perhaps 3-4 years ago. Of course both got better as it seems, but having latest drivers usually -not always- means generally more stable machine.

    By the way, seriously… Why still people bother about RAM? I’m not the one to judge, but nowadays RAM has become overabundant. Even mobiles have 2GB. For me always matters efficiency in CPU/GPU utilization and here unfortunately only Edge exceeds by far.

    1. Seb said on January 26, 2017 at 9:10 pm

      Because RAM equals efficiency in certain conditions. Lacking RAM means your system slows down to a crawl.

      And while I’m not sure about it, it’s possible that a program that allocates RAM too liberally will encounter performance issues, that there are gains to be had in organizing and minimizing your data in RAM.

  3. pd said on January 26, 2017 at 5:15 pm

    Still waiting for a few add-ons to update. Don’t think they will any time soon though :(

    The bullshit around Stylish is a nightmare. Sage RSS project appears dead and with Mozilla yet to write an API for the sidebar, it can’t be updated yet.

  4. Doc said on January 26, 2017 at 3:24 pm

    “…but nothing to major.” *too* – too big, too small, two O’s, Martin. :)

  5. Dhananjay said on January 26, 2017 at 3:14 pm

    yes i am using multi-process already, so far performance is good and recent update to firefox 51 it drives it further

  6. lainiwaku said on January 26, 2017 at 11:37 am

    “This is not a problem on modern systems with 8, 16 or even more Gigabytes of RAM,”
    This IS a problem, a can’t even run a high demanding videogame while running firefox on second screen ….

    1. Ben said on January 26, 2017 at 5:35 pm

      Yes it’s indeed a problem. I have 24GB+4GB swap and I hit the limit like every day (meaning, Windows will force-crash some programs because it needs memory). If I’d were to switch to chrome I’d need quite some more. And I don’t even have anything special like a game or photoshop/premiere/whatever running. Just everyday stuff.

      1. Seb said on January 26, 2017 at 9:05 pm

        Yeah I don’t know if that’s still the case but until at least Windows 7, I think it was recommended to have a swap file about as big as your RAM. See how it works for you!

      2. akupa said on January 26, 2017 at 8:09 pm

        Hello, you certainly need bigger swap. I have similar problem with 16GB ram, Windows notify low free memory when I have used more the 10GB.

        After i set up bigger (or system automatically managed) pagefile, problem are go.
        Have a nice day!

    2. Seb said on January 26, 2017 at 3:22 pm

      Yeah RAM consumption remains a thing no matter how much RAM you have, partly because programs consume more as more is available, and partly because people expect to be able to run more programs concurrently. Especially content creators and developers, but gamers too.

  7. JohnCock said on January 26, 2017 at 9:58 am

    Or there could be a dynamic variable that sets the default amount of processes depending on the information firefox gets about the hardware its running on. Or a gui or setting via about:config for the user to be able to modify the values to their wishes?

  8. Ben said on January 26, 2017 at 9:49 am

    How often do these always referred-to “tab crashes” happen?
    I have tons of open tabs and I cannot remember the last time that happened.

    1. Seb said on January 26, 2017 at 3:08 pm

      I never have any crash either. But there are many other advantages to having a multi-process architecture. It’s just better all around, except for RAM.

      Chrome opened the way but that was a long time ago. Mozilla and others before it have improved on the concept since then. The next technological leap comes from Mozilla this time with Quantum, and the virtuous circle goes on.

    2. Psy said on January 26, 2017 at 12:26 pm

      Once again, it’s not the number of tabs the problem. But WHICH, and how many addons are loaded, and which too.

    3. ShintoPlasm said on January 26, 2017 at 10:54 am

      Agree with Ben. I honestly can’t remember the last time Firefox has actually crashed on me, and I’ve been using it for quite a few years… Opera and Chrome have certainly crashed more often (although not really that much, tbh).

    4. JohnCock said on January 26, 2017 at 9:55 am

      I have crashes now and then. Not related to my browser or hardware. But more likely badly integrated javascripts that makes the website going down to a halt.

  9. happysurf said on January 26, 2017 at 9:21 am

    Martin, the Firefox multi-process is different from Chrome but I see on your Task Manager a lot of RAM used by Nightly.
    I’m afraid that at the end consumes the same amount of memory of Chrome implementation. :-(

    1. Seb said on January 26, 2017 at 3:02 pm

      Well that’s to be expected in Nightly. One big part of the work is to figure out where RAM is wasted and can be regained as # of content processes are increased.

      So RAM consumption right now in nightly, where just today the second content process has been enabled, is likely to be higher than RAM consumption in Firefox Release whenever it gets 2+ content process by default.

      The goal Mozilla have is:
      1 content process: +20% RAM
      2 content processes: +40% RAM
      4 content processes: +75% RAM
      8 content processes: +140% RAM

      It’s +X% versus Firefox without multi-process, so If you use 300Mb normally and enable 2 content processes, Mozilla expects Firefox to require 420Mb. I can confirm that for me at least, the +20% is respected. We’ll have to see once the features hit release if 2+ stay in line with stated goals.

    2. Martin Brinkmann said on January 26, 2017 at 1:50 pm

      I’d imagine that you’d come out about the same, or even on top of what Chrome uses currently if you’d open the same number of processes and sites in both browsers. But Mozilla won’t follow Chrome, so there is still less RAM use when you use Firefox.

Leave a Reply

Check the box to consent to your data being stored in line with the guidelines set out in our privacy policy

We love comments and welcome thoughtful and civilized discussion. Rudeness and personal attacks will not be tolerated. Please stay on-topic.
Please note that your comment may not appear immediately after you post it.