Firefox Quantum Eats RAM Like Chrome

For a long time, Mozilla’s Firefox has been my web browser of choice. I have always preferred it to using Google’s Chrome, because of its simplicity and reasonable system resource (especially RAM) usage. On many Linux distributions such as Ubuntu, Linux Mint and many others, Firefox even comes installed by default.

Recently, Mozilla released a new, powerful and faster version of Firefox called Quantum. And according to the developers, it’s new with a “powerful engine that’s built for rapid-fire performance, better, faster page loading that uses less computer memory.”

Read Also: How to Install Firefox Quantum in Linux

However, after I updated to Firefox Quantum, I noticed two significant changes with by far the biggest update to Firefox: first, it is fast, I mean really fast, and secondly, it’s greedy of RAM just like Chrome, as you open more tabs and continue to use it for a long time.

Therefore I carried out an simple investigation to examine Quantum’s memory usage, and also tried to compare it to Chrome’s memory usage, using the following testing environment:

Operating system - Linux Mint 18.0
CPU Model        - Intel(R) Core(TM) i3-3120M CPU @ 2.50GHz                                                            
RAM 		 - 4 GB(3.6 Usable)

Firefox Quantum Eats RAM With Many Tabs Opened

If you open Quantum with just few tabs, let’s say up to 5, you’ll notice that memory consumption by Firefox is fairly good, but as you open more tabs and continue to use it for long, it tends to eat up RAM.

I performed a few tests using glances – a real-time Linux system monitoring tool, to view top process by RAM usage. Under this tool, to sort processes by RAM usage, simply press m key.

I started by running glances and sorting processes by highest RAM usage before launching Firefox, as shown in the screenshot below.

$ glances 
Glances - Processes Memory Usage
Glances – Processes Memory Usage

After launching Firefox and using it for close to half an hour with less than 8 tabs open, I captured a screenshot of glances with processes sorted by RAM usage shown below.

Glances - Firefox Memory Usage Monitoring
Glances – Firefox Memory Usage Monitoring

As I continued using Firefox through the day, the memory usage was steadily increasing as seen in the next screen shot.

Glances - Firefox Memory Usage Increasing
Glances – Firefox Memory Usage Increasing

At the end of the day, Firefox had already consumed more than 70% off my system RAM as shown by the red warning-indicator in the following screen shot.

Note that during the test, I did not run any other RAM-consuming applications apart from Firefox itself (so it was definitely the one consuming the most amount of RAM).

Glances - Firefox High Memory Usage
Glances – Firefox High Memory Usage

From the results above, Mozilla was rather misleading in telling users that Quantum uses less computer memory.

Having known Chrome for eating RAM, the following day, I decided to also compared its (Quantum’s) memory usage with Chrome as explained in the next section.

Firefox Quantum Vs Chrome: RAM Usage

Here, I started my test by launching both browsers with the same number of tabs and opening the same sites in corresponding tabs as seen in the screen shot below.

Opened Same Tabs on Firefox and Chrome
Opened Same Tabs on Firefox and Chrome

Then from glances, I watched their RAM usage (sorted processes by memory usage as before). As you can see in this screenshot, considering all Chrome and Firefox processes (parent and child processes) on average Chrome still consumes more percentage of RAM than Quantum.

Compare Chrome and Firefox Memory Usage
Compare Chrome and Firefox Memory Usage

To better understand memory usage by the two browsers, we need to clearly interpret the output the meaning of the %MEM, VIRT and RES columns from the process list headers:

  • VIRT – represents the total amount of memory a process is able to access at the moment, which includes RAM, Swap and any shared memory being accessed.
  • RES – is the accurate representation of how much amount of resident memory or actual physical memory a process is consuming.
  • %MEM – represents the percentage of physical (resident) memory used by this process.

From the explanation and values in the screenshots above, Chrome still eats more physical memory than Quantum.

All in all, I suppose Quantum’s speedy new engine, that ships in with many other performance improvements speaks for its high memory utilization. But is it worth? I would like to here from you, via the comment form below.

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Aaron Kili
Aaron Kili is a Linux and F.O.S.S enthusiast, an upcoming Linux SysAdmin, web developer, and currently a content creator for TecMint who loves working with computers and strongly believes in sharing knowledge.

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40 thoughts on “Firefox Quantum Eats RAM Like Chrome”

  1. I am the sort of user that loves tabs and I leave them up for far too long. I have not noticed any memory issues with Quantum but have not examined it as you have. I like the new speed of Firefox, feel sure its memory use has improved and have started to replace Chrome with it even on Android devices.

    On a 12 Yr old laptop with only 2Gb RAM I have zRam installed and this seems to keep Firefox memory use efficient. I also use a PC and laptop with 8Gb and they do fine, though sometimes didn’t pre-Quantum. I’m a fan!

    • @Ron

      What are your system specifications? You should note that my previous updates have not been like this, this has been specific to Quantum, and many long time Firefox users have also complained about Quantum’s memory usage.

  2. Both Web browsers are horrendous for eating up RAM like it was going out of style. I upgraded my main PC to 16 GB, and right now, with running ONLY Firefox, gedit, shutter, and three terminal sessions, I am at 788 MB free.

    So it looks like my next machine or motherboard will have to have at least double that amount (i.e., 32 GB) and if I can afford it, I will go up to 64 GB. I got the extra RAM to allow me to run virtual machines in Oracle VirtualBox but that’s so hard to do, especially Windows 10 in a VM. Just because of my web-browsers.

    Oh, and Chrome on Linux? Forget it. It brings my system (quad-core and lscpu reports (Intel(R) Core(TM) i3-4150 CPU @ 3.50GHz), but nonetheless to an absolute crawl, to the point I can’t even use even a one-tab session of Chrome. What the h??? is going on here?

    • @John

      Firefox’s memory consumption was good before the Quantum update. And we have all known Chrome for being greedy of RAM. But Firefox Quantum and Chrome are now more or less the same, in terms of memory usage.

  3. I have 63 tabs open in FireFox 57.0.4 (64bits) running on Linux Mint 18.3 with kernel 4.14.13 on a Dell laptop with 8 GB RAM and it consumes 340 MB.

    There are two things I have done which are not default behavior and that is adding following settings in about:config.

    network.http.pipelining       true
    network.http.pipelining.ssl true
    layers.acceleration.force-enabled  true

    In the past (months ago) I noticed a continuous increase in RAM usage probably caused by a memory leak. I haven’t seen while using Quantum.

  4. Fortunately, RHEL and CentOS are stuck at Firefox 52 ESR.

    Windows 64-bit users can swap Firefox for Waterfox, which will be Firefox 56 ESR equivalent.

    Both versions are fast enough and, more importantly, support all the original extensions, like TabMixPlus, which has no replacement.

  5. I have a modern desktop computer with 8 GB of RAM. I don’t notice any performance degradation due to the new version of Firefox Quantum. It may have an impact on older machines for sure. Nothing new with this situation, it has been happening since the beginning of the personal computers, new software may mean new hardware.

    • @Martins

      That is true, but all other previous updates have not had such an effect, i mean necessitating for new hardware(as you have suggested). This is the first time it is really happening, and by the way many Firefox lovers are complaining about Quantum.

  6. Interesting article. I was confused about the last conjecture though — Isn’t chrome and its subprocesses using less RES memory than firefox? I personally don’t care about memory usage, but it just seems odd that the numbers on screen don’t match with the conclusion. Keep up the good work.

    • @Jorma

      I suppose we have used the wrong screen shot for the conclusion section, because when you look at it carefully, the output shows processes sorted by CPU usage not memory usage.

      We will correct this as soon as possible. Thanks for the heads up.

      • @Jorma

        We have put the right image for the comparison of memory usage between Quantum and Chrome section. Once again, thanks for the great concern and for the feedback as well.

  7. Thank you for the article!

    I’m so disappointed with Firefox since this Quantum version. As you, I’ve always preferred Firefox, specially at work, in which I have at least a dozen tabs open, sometimes tens.

    Since the Quantum version, I end up my day closing the browser because it becomes unresponsive, my pc apps starts hanging up and getting slow.

    Have you submitted already your test results to Mozilla?

    • @swon

      Quantum is frustrating my efforts at work too, i have always like Firefox but this latest version seems to be problematic. I need to understand how to deliver my findings in the appropriate manner, but i will do that as soon as possible.


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