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 Responses

  1. THE_ANONYMOUS says:

    I think Firefox Quantum 68 simply has a severe memory leak. Looking at the process in ‘top’ (not glances, I didn’t think to use it at the time), I can sit there and just watch the RAM get sucked into a useless vortex of unused JavaScript objects. That, and the browser itself recruited no less than 107 sub-threaded processes to run: (drumroll please)…..

    ONE. SINGLE. TAB!!!!!!!!!!


    Oh, and ‘glances‘ shows that it uses 5.84GB of my RAM to do so. Guess what tab it was?
    It was THIS one, for THIS site, to post THIS. VERY. MESSAGE.

    I’m off to find a browser with a smaller memory footprint now. This is just plain loony. I hope Mozilla gets its act together again soon—and GNOME, too.

  2. Max Peace says:

    There is no possible justification for a web browser to use up 2GiB of ram by the end of the day (ff quantum 61.0.1 64bit on xubuntu 18.04) with only 6 tabs open, RT on pause, 2 paused youtubes and 3 very simple static html pages. It’s a disgrace to the programming profession and mozilla should be ashamed of themselves.

    • Aaron Kili says:


      Am facing the same problems on a daily basis, my laptop now freezes a lot. It even gets worse when i open other applications such as VS Code which also consumes a lot of RAM. This surely needs to be checked by Firefox developers.

    • John Bijnens says:

      You could try the following.

      1. Go to preferences.
      2. Under the tab “General”, disable the options “Use recommended performance settings” and “Use hardware acceleration when available”. Set “Content process limit” to 2.
      3. Disable prefetching (this is also a nightmare with Chrome)

  3. Jon says:

    Bloody hell, the new 58 Quantum is now running processes under System (NT Kernel & System) on a win7, causing the CPU to average 50~75% just idling. This CPU utilization was never this bad with 57, Chrome64 and IE11 use far less CPU.

  4. swon says:

    A new release is available:

    For me, I hope this fix is enough to overcome the problems I experienced: Loading pages faster by changing how Firefox caches and retrieves JavaScript.

  5. tomas_arad says:

    On my MSI GTX 700 old notebook, with 2G RAM – running Solus 3 MATE, – I can use decently Firefox, after 10h with 4 or 5 tabs open, I freeze the system. But with Chrome, freeze the system in 1h or less.

    Vivaldi, I don’t now how, have better performance, but not like Firefox.

    I notice, the memory usage is higher if I have Facebook and other sites notifications set to allow, in all web browser.

    Its my experience, I’m not geek, tech people – I’m graphic designer.

    Kael have right, if I have to do some work, (using: Inkscape, Gimp, Scribus, Atril ) I turn off and close all cloud service, skype, web browser, nitroshare to have enough RAM to work.

    Years a go the web browser not was a problem.

  6. J. Holmes says:

    Don’t notice it on newer system but on an older one, it’s almost unusable the more tabs I open and the longer I leave computer open and Chromium is a better option now(!).

  7. Kael says:

    Unused memory is a waste.

    If you on the other hand NEED to run multiple applications at the same time and do heavy stuff like blender, gimp… well, then you should focus on getting a more and BETTER ram.
    4gb is not enough to run gnome and browser in a complete experience.


    • Aaron Kili says:


      Yes, “Unused memory is a waste”, but if a single software is designed to consume all RAM, then it is not reliable. And I will add more RAM to my system, i simply got curious about Quantum’s memory usage because all other previous updates did not have this kind of effect.

    • Testertime says:

      In all honesty, this whole “unused RAM is wasted RAM” thinking is the root cause why programs eat up so incredibly much memory and behave wasteful in general these days. When all developers also assume it’s just fine to add their shiny software to autostart, what do you think does this mindset when it comes to memory usage of their applications? Yeah, everything gets shameless. Using as much as possible just because it’s possible is a wasteful mindset – in my opinion, yes. Memory is there to be used for real stuff, and not make developers lazy.


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