Entering the Quantum Era—How Firefox got fast again and where it’s going to get faster

People have noticed that Firefox is fast again.

Tweet from Sara Soueidan about Firefox Nightly being fast

Over the past seven months, we’ve been rapidly replacing major parts of the engine, introducing Rust and parts of Servo to Firefox. Plus, we’ve had a browser performance strike force scouring the codebase for performance issues, both obvious and non-obvious.

We call this Project Quantum, and the first general release of the reborn Firefox Quantum comes out tomorrow.

orthographic drawing of jet engine

But this doesn’t mean that our work is done. It doesn’t mean that today’s Firefox is as fast and responsive as it’s going to be.

So, let’s look at how Firefox got fast again and where it’s going to get faster.

Laying the foundation with coarse-grained parallelism

To get faster, we needed to take advantage of the way hardware has changed over the past 10 years.

We aren’t the first to do this. Chrome was faster and more responsive than Firefox when it was first introduced. One of the reasons was that the Chrome engineers saw that a change was happening in hardware and they started making better use of that new hardware.

Chrome looking to the future of coarse-grained parallelism

A new style of CPU was becoming popular. These CPUs had multiple cores which meant that they could do tasks independently of each other, but at the same time—in parallel.

This can be tricky though. With parallelism, you can introduce subtle bugs that are hard to see and hard to debug. For example, if two cores need to add 1 to the same number in memory, one is likely to overwrite the other if you don’t take special care.

diagram showing data race between two cores

A pretty straightforward way to avoid these kinds of bugs is just to make sure that the two things you’re working on don’t have to share memory — to split up your program into pretty large tasks that don’t have to cooperate much. This is what coarse-grained parallelism is.

In the browser, it’s pretty easy to find these coarse grains. Have each tab as its own separate bit of work. There’s also the stuff around that webpage—the browser chrome—and that can be handled separately.

This way, the pages can work at their own speed, simultaneously, without blocking each other. If you have a long-running script in a background tab, it doesn’t block work in the foreground tab.

This is the opportunity that the Chrome engineers foresaw. We saw it too, but we had a bumpier path to get there. Since we had an existing code base we needed to plan for how to split up that code base to take advantage of multiple cores.

Firefox looking to coarse-parallelism future

It took a while, but we got there. With the Electrolysis project, we finally made multiprocess the default for all users. And Quantum has been making our use of coarse-grained parallelism even better with a few other projects.

timeline for coarse grained parallelism, with Electrolysis and Quantum Compositor before initial Quantum release and Quantum DOM after


Electrolysis laid the groundwork for Project Quantum. It introduced a kind of multi-process architecture similar to the one that Chrome introduced. Because it was such a big change, we introduced it slowly, testing it with small groups of users starting in 2016 before rolling it out to all Firefox users in mid-2017.

Quantum Compositor

GPU process

Quantum Compositor moved the compositor to its own process. The biggest win here was that it made Firefox more stable. Having a separate process means that if the graphics driver crashes, it won’t crash all of Firefox. But having this separate process also makes Firefox more responsive.

Quantum DOM

Even when you split up the content windows between cores and have a separate main thread for each one, there are still a lot of tasks that main thread needs to do. And some of them are more important than others. For example, responding to a keypress is more important than running garbage collection. Quantum DOM gives us a way to prioritize these tasks. This makes Firefox more responsive. Most of this work has landed, but we still plan to take this further with something called pre-emptive scheduling.

Making best use of the hardware with fine-grained parallelism

When we looked out to the future, though, we need to go further than coarse-grained parallelism.

Firefox looking towards the future of fine-grained parallelism

Coarse-grained parallelism makes better use of the hardware… but it doesn’t make the best use of it. When you split up these web pages across different cores, some of them don’t have work to do. So those cores will sit idle. At the same time, a new page being fired up on a new core takes just as long as it would if the CPU were single core.

Splitting content windows across different cores

It would be great to be able to use all of those cores to process the new page as it’s loading. Then you could get that work done faster.

But with coarse-grained parallelism, you can’t split off any of the work from one core to the other cores. There are no boundaries between the work.

With fine-grained parallelism, you break up this larger task into smaller units that can then be sent to different cores. For example, if you have something like the Pinterest website, you can split up the different pinned items and send those to be processed by different cores.

Splitting work across cores fine-grained

This doesn’t just help with latency like the coarse-grained parallelism did. It also helps with pure speed. The page loads faster because the work is split up across all the cores. And as you add more cores, your page load keeps getting faster the more cores you add.

So we saw that this was the future, but it wasn’t entirely clear how to get there. Because to make this fine-grained parallelism fast, you usually need to share memory between the cores. But that gives you those data races that I talked about before.

But we knew that the browser had to make this shift, so we started investing in research. We created a language that was free of these data races — Rust. Then we created a browser engine— Servo — that made full use of this fine-grained parallelism. Through that, we proved that this could work and that you could actually have fewer bugs while going faster.

timeline of fine grained parallelism, with Quantum CSS before initial Qunatum release, and Quantum Render and possibly more after

Quantum CSS (aka Stylo)

Cores that have finished their work stealing from the core with more work

With Stylo, the work of CSS style computation is fully parallelized across all of the CPU cores. Stylo uses a technique called work stealing to efficiently split up the work between the cores so that they all stay busy. With this, you get a linear speed-up. You divide the time it takes to do CSS style computation by however many cores you have.

Quantum Render (featuring WebRender)

Diagram of the 4 different threads, with a RenderBackend thread between the main thread and compositor thread. The RenderBackend thread translates the display list into batched draw calls

Another part of the hardware that is highly parallelized is the GPU. It has hundreds or thousands of cores. You have to do a lot of planning to make sure these cores stay as busy as they can, though. That’s what WebRender does.

WebRender will land in 2018, and will take advantage of modern GPUs. In the meantime, we’ve also attacked this problem from another angle. The Advanced Layers project modifies Firefox’s existing layer system to support batch rendering. It gives us immediate wins by optimizing Firefox’s current GPU usage patterns.


We think other parts of the rendering pipeline can benefit from this kind of fine-grained parallelism, too. Over the coming months, we’ll be taking a closer look to see where else we can use these techniques.

Making sure we keep getting faster and never get slow again

Beyond these major architectural changes that we knew we were going to have to make, a number of performance bugs also just slipped into the code base when we weren’t looking.

So we created another part of Quantum to fix this… basically a browser performance strike force that would find these problems and mobilize teams to fix them.

timeline of Quantum Flow, with an upward sloping arc

Quantum Flow

The Quantum Flow team was this strike force. Rather than focusing on overall performance of a particular subsystem, they zero-ed in on some very specific, important use cases — for example, loading your social media feed — and worked across teams to figure out why it was less responsive in Firefox than other browsers.

Quantum Flow brought us lots of big performance wins. Along the way, we also developed tools and processes to make it easier to find and track these types of issues.

So what happens to Quantum Flow now?

We’re taking this process that was so successful—identifying and focusing on one key use case at a time — and turning it into a regular part of our workflow. To do this, we’re improving our tools so we don’t need a strike force of experts to search for the issues, but instead can empower more engineers across the organization to find them.

But there’s one problem with this approach. When we optimize one use case, we could deoptimize another. To prevent this, we’re adding lots of new tracking, including improvements to CI automation running performance tests, telemetry to track what users experience, and regression management inside of bugs. With this, we expect Firefox Quantum to keep getting better.

Tomorrow is just the beginning

Tomorrow is a big day for us at Mozilla. We’ve been driving hard over the past year to make Firefox fast. But it’s also just the beginning.

We’ll be continuously delivering new performance improvements throughout the next year. We look forward to sharing them with you!

Try Firefox Quantum in Release or in Developer Edition to make sure you get the latest updates as they come out.

About Lin Clark

Lin works in Advanced Development at Mozilla, with a focus on Rust and WebAssembly.

More articles by Lin Clark…


  1. bornjre

    i developer edition about two weeks ago loved ui but after some time my laptop fan went nuts, i was running only two tabs (one being youtube) and nothing much. it must be sorted out now. excited for new fox :D

    November 13th, 2017 at 08:44

    1. David

      The point of parallelization is to harness the full power of the CPU. If you don’t want that try reducing the content process limit near the bottom of general options.

      November 13th, 2017 at 19:09

    2. Julian

      You should install h264ify extension. That will almost certainly stop the high CPU usage when using youtube.


      November 14th, 2017 at 04:38

    3. anon

      Is Quantum a seperate product form regular firefox? Or should I expect to see these changes with my regular updates?

      November 14th, 2017 at 07:05

      1. Lin Clark

        You can expect to see these changes with your regular updates.

        November 15th, 2017 at 10:40

  2. Zorg

    Nice job. Looking forward to a more detailed 2018 roadmap then.

    I also look forward to the day where Mozilla isn’t afraid to let Firefox for Android piggyback on Firefox’s product quality and acknowledgement.

    November 13th, 2017 at 08:55

  3. Marty

    I appreciate your dedication and hard work. I was a devoted Firefox user because of the customizability, but I strayed to Chrome and Slimjet for the speed. Now I’m ready to rejoin the Firefox family and as I’ve been promised take advantage of the new speedster on the block. Good Luck!

    November 13th, 2017 at 08:59

    1. John

      Well, this is the problem these days. People don’t have principles, they go where is more “warm”.. You stick with a FREE browser that respects your privacy, or you pee on everything for a little speed. You think it was easy defending a country/city/village? Why not invite the enemy, sell your town for a shinny mirror or something …

      How much have you donated to Mozilla ?
      Privacy is dead because of folks like you. Sorry, it is just the truth, hard.

      November 13th, 2017 at 17:52

      1. Adam

        Well that escalated quickly

        November 14th, 2017 at 02:07

      2. Zoidberg

        This is very true. And now thanks to all those people who only care about “speed”, we end up with a Chrome clone with barely a fraction of the good extensions it used to have… Cookie Manager+? Gone. Tamper Data? Gone. RefControl? Gone. TabGroups Manager? Gone. YesScript? Gone. Small Tabs? Gone. All I’m left with is Ghostery, uBlock, and HTTPS Everywhere. Wow, that’s so awesome!

        I remember of a time when Firefox was interesting for its extensions. Now it’s just “Chrome with privacy”. Better than nothing, but a lot worse than before, and no other option anyway because of folks like Marty.

        November 14th, 2017 at 02:35

        1. Heinzel

          I was a true believer and defender of Firefox since the beginning. The GUI was superior and you could modify every setting to your liking. When Google thinks its time to remove the backspace to go back functionality from Chrome (and they did), you are out of luck (except of a few addons).

          But then it comes to a point where the use of Firefox becomes unbearable and you have no other choice but to look for alternatives.

          Have over 10000 bookmarks like me? If you accidently hover over “Bookmarks” Firefox will be completely stuck for 30 seconds, because it tries to load all bookmarks at once, even though it can only display a fraction.

          Have over 500 Tabs open? Impossible on Firefox. Firefox became extremely slow after I opened 20 video tabs. Admittedly, Chrome takes 32GB RAM when I have my 500 Tabs open, but I scale my system to my needs.

          The switch was not easy and I lived with those problems for years. Tried switching to Chrome multiple times but it was just shitty. I hated Chrome’s interface and it’s tabbing. I had to heavily rely on addons and got used to it after I got sick about Firefox’ performance. I’ll take a look at Quantum, but I have a feeling that the bookmarks bug is still not fixed.

          November 14th, 2017 at 06:40

        2. Will

          You’re talking utter nonsense. I used to use Firefox avidly until release after release got slower and slower until it was literally unusable on my machine. At that point I tried Chrome and was pleased to find it was, shock horror, usable. It remained usable (and has led the way with dev tools) and so I continued using it. It was never about Chrome being faster and shinier, it was about Firefox going completely off the rails with it’s obsession with skins and bloated UI.

          Quantum has caught my interest and so I am now willing to give Firefox another chance. Sorry if that infringes on your exclusive club. Over time I am sure the addons will return, they’ll just need to make sure they don’t bloat the browser and send it back on the downward spiral it was on for many many years.

          November 14th, 2017 at 08:28

        3. Beardface

          The reason we have to focus on speed is because the modern web is a disgusting, bloated mess of javascript, CSS, and redirects. Even now, with _any_ browser, the web is barely usable.
          Opera is no longer 3 MB because it’s had to become safer, faster, and the standard technology the web uses has become substantially more inexplicably complicated. All of that takes more code.

          TL;DR: the web is the problem, not browser vendors.

          November 14th, 2017 at 09:58

        4. Derrick

          Uh… bro, the addons will eventually be updated and comeback. That’s how technology works, especially the Open Source.

          Things update. Outdated stuff that relies on specific bases that have undergone change will no longer function properly. Devs have to accommodate for that.

          Thew new Firefox, if it attracts more users for its speed will more than likely get even more addons for it.

          November 14th, 2017 at 11:08

        5. Tim

          Don’t pretend it’s “folks like Marty”. It’s general human behavior. And even if you could change the 6,000,000,000 or so humans that have the same instincts as Marty, by the time you got done, they’d all be dead and there’d be a whole new batch of 12,000,000,000 humans with the same behavior, over again.


          November 14th, 2017 at 16:42

        6. Ray

          And it’s not pretty anymore. I miss the cute buttons and the interface. Noia buttons please.

          November 14th, 2017 at 18:28

        7. Didunaffin

          It’s the job for developers to adapt these extensions.

          And a protip, don’t use ghostery.

          November 14th, 2017 at 21:51

        8. devx

          And people like you those who discourage others from trying out new things and moving the wheel forward. The chromium project is one of the best things to happen to the tech world in recents years which has laid the path for many cool technologies (v8, nodejs, electron etc.) and is also the best thing to happen to Mozilla/Firefox. Competition always moves the world forward, not the opposite.

          November 15th, 2017 at 00:02

      3. cronvel

        … not to mention that Firefox has almost always being faster than Chrome.

        Chrome has a faster Javascript engine, but overall performance are not that good, except in benchmark and demo/game. For regular browsing (what you do 95% of the time, if not 99%), Firefox wins, especially when you have many tabs opened. And what about Chrome’s huge memory consumption?

        Instead of trusting benchmarks, people should trust their own experience…

        November 14th, 2017 at 09:40

  4. KSS

    Hi Lin, great article. Thanks for the illustrations. I am only tangentially interested in the inner works of the technology here and I would not have read the entire article without them.

    November 13th, 2017 at 09:24

  5. Ryan S.

    Hat’s off to everyone involved in Project Quantum! Great write up, Lin.

    November 13th, 2017 at 10:38

  6. Jad

    You’ve just won me back, I hope that I can have all of my data imported from Vivaldi without issues.

    November 13th, 2017 at 11:09

    1. Omar

      I really like Vivaldi’s approach to things, but the “built with the web for the web” way is making things glitch for me in a low end machine, even using more ram than chrome.
      It would be really great if they can ditch chromium and go Servo & Rust, so we can combine the customizability with performance
      Also I think that Firefox should give customizability and new features more focus

      November 14th, 2017 at 09:57

  7. Daniel

    I am so happy to see Firefox shining again.
    Congratulations to all developers!

    November 13th, 2017 at 11:41

  8. Raymond Ramirez

    When Firefox began, I was one of the first subscribers. I stopped using Firefox after upgrading to Windows 10. So I will install and try out the latest version after it is released.

    November 13th, 2017 at 11:47

  9. a

    Cute drawings, but where are the benchmarks?

    November 13th, 2017 at 12:19

    1. Jon

      They have a website where they have automated test results updated frequently: https://arewefastyet.com/

      November 13th, 2017 at 15:25

  10. James

    amazing! thanks for putting in the hard work that makes it easier for the rest of us to move away from having our own data sold :) i’ve been using chrome for a long time out of what felt like necessity and and i’m excited to make the switch back to my first love

    November 13th, 2017 at 12:47

  11. QuantumBreak

    Performance increase – well done. But what about minor issues that are part of firefox for years and years? One issue was not to delete indexedDB – as soon as media started focussing that topic, you suddenly were able to fix that issue in no time.
    An other issue is the parent folder (aka path) in bookmark search. This is an issue which is part of Firefox since more than 10 years ago – and Quantum kills the only workaround (3rd party extensions Go Parent Folder and Show Parent Folder)

    November 13th, 2017 at 13:19

  12. Garrett Jewell

    Congratulations. This is a big accomplishment. I’m looking forward to signing up for the beta channel.

    November 13th, 2017 at 13:27

  13. Mees Boeijen

    Congratulations guys! Since the Quantum-release of Firefox Developer Edition I’ve been using Firefox more than ever.

    November 13th, 2017 at 13:45

  14. Jon v

    It’d be interesting to see whether rendering a page on a GPU is more efficient from a performance per watt perspective than just rendering on a multicore CPU, and is that vendor specific (Nvidia vs. AMD vs. Intel vs. mobile GPU, Mac vs. PC vs. Linux vs iOS vs. Android). What does it do to battery life of a laptop or mobile device when it’s constantly spinning up and down the GPU?

    November 13th, 2017 at 14:14

  15. Frans Faase

    Since about two weeks, I am having problems with typing texts. The characters appear only after some delay and often are scrambled. Especially spaces are moved to the end. But also the caps loc state is kept, resulting in multiple capitals at the start of a new sentense. Even typing a simple password is becoming a problem. Closing and reopening Firefox seems to solve the problem. I only have about five to seven tabs open.

    November 13th, 2017 at 14:42

  16. Juraj

    I love it!
    And my add-on Group Speed Dial is now even faster!

    November 13th, 2017 at 15:05

  17. Harry

    I have always loved FF for its philosophy and open source principals. Have been using chromium for Dev tools (now also available in Firefox YAY!) looking forward to the release.
    Well done you

    November 13th, 2017 at 15:21

  18. Dr. E.J. Wilson

    I was impressed with the speedup going to version 56, I’m really looking forward to 57. Thanks for your efforts!

    November 13th, 2017 at 15:25

  19. Abed

    I picked up developer edition a few weeks ago and never looked back. To all those involved, great work!

    November 13th, 2017 at 15:59

  20. Mark

    How will this affect waterfox???
    Will there be updates to the 64 bit platform browser as well?? Hope so!!
    Love the Waterfox Browser!!!

    November 13th, 2017 at 17:06

  21. Steven Greenberg

    I did some parallelization work on electronic circuit simulators back in the 1980s. It is nice to see how the technology has progressed over the years – both hardware and software.

    November 13th, 2017 at 17:14

  22. Sean

    Speed may now be FF’s friend, which is great – just tested and indeed it was slightly faster than Chrome. However, image saturation is nasty. I’m not a dev, but for that reason, for now, I’ll continue to use Chrome.

    November 13th, 2017 at 17:39

  23. Eric

    Some low hanging fruit for speed:

    Prioritize content hosted my the page being visited. Google will never do this because that would make their ad revenue take a hit.

    On a related thought minimize the priority of known ad services, better yet native ad blocking.

    Use clues on the pages themselves to figure our why someone when to that page and bump that content to the highest priority. On video sites, load video content first; photo sites, images first…etc.

    I guess these are more like perceived speed increases for the end user versus actual speed increases. Perception is powerful.

    November 13th, 2017 at 17:40

  24. jake

    so firefox can continue to be #1 sweet! glad you guys are doing something though been along time needed.

    Just please 1 thing.
    PLEASE dont let firefox turn into the Ram Goblin like chrome did.

    November 13th, 2017 at 18:25

  25. Milt Reynolds

    Lin, what a great article! I clicked through a link from How-to-Geek, but I expected to understand little to nothing, since I am far from being anywhere near a developer. But I did understand it! Amazing! Thank you for the article. I plan to return to Firefox and try it out.

    November 13th, 2017 at 19:08

  26. Nope nope nope

    I uninstalled Firefox and switched to Waterfox, since Firefox Quantum would have killed 60% of my extensions.

    Extensions and browser extendability are the reason Firefox exists. You kill that, you kill Firefox.

    November 13th, 2017 at 20:14

  27. Jim

    I don’t think this accurately represent how long it took for e10s to be testable.
    The first time I’ve seen *actual* e10s was in FirefoxOS when .. Chris Jones? I think? and Guillaume? added the actual process separation (and this was after a lot of ground work had been also already done by several other people). At that time I though it would take off and it felt like a corner stone, though in reality, it really took off later.
    A basic sandbox shortly followed and a little later, Desktop Firefox on Linux could use it, granted that you recompiled it, because it used the same code as FirefoxOS.
    This was in something like 2014 (I might be off by a bit, was it 2013? I guess hg has the date) and work was already in progress in 2011.

    I believe Mozilla started to much more seriously commit resources to this in 2016 though (which is great). So much work by so many people, and I’m happy with how fast this new version is by the way!

    November 13th, 2017 at 20:29

  28. Clinton

    What’s the point when nearly all my addons, plugins and extensions are no longer compatible? Almost useless. Mozilla continues to shoot itself in the foot in this regard. Used to be my daily driver years ago. Now … never use it. Tired of Mozilla changing the game every few months.

    November 13th, 2017 at 20:29

  29. bob

    Definitely fast!

    November 13th, 2017 at 20:30

  30. matt

    Good work.

    Not sure if this fits in with the current optimizations.. energy consumption?

    November 13th, 2017 at 20:54

  31. Quantum DOM already intoduced in Firefox 57?

    Is Quantum DOM already intoduced in Firefox 57?
    Here’s what I found on ghacks:
    >There’s more to come though. Quantum has 5 parts, 4 major ones. Out of these 4 only two are shipped with Firefox 57. A large one, WebRender, is planned for 59. The other missing is Quantum DOM, about which I don’t know enough to tell how big it is when it comes to performance, smoothness and responsiveness matters.

    November 13th, 2017 at 20:57

  32. Konstantin

    It would also be great to see the graphs for the below stats:
    – amount of users switched to FF 57
    – amount of people staying at various ESR versions as long as possible (due to XUL supported revoked from FF 57)
    – amount of users stopped using FF altogether

    According to
    the overall porting situation is rather sad (partially because of WebExtensions API changing way too often for a stable platform).

    Let’s see the numbers.

    November 13th, 2017 at 21:10

    1. dsfsdfdsf

      And that list is far from complete…


      November 14th, 2017 at 10:24

  33. Jason

    I’m not finding it any faster, it still leaks memory like crazy if I leave things in pinned tabs running overnight.

    November 13th, 2017 at 21:28

  34. Joe Contreras

    way to go for the team @ Firefox!
    This is a tremendous effort as harnessing the power of new hardware in such an innovative way is challenging to say the least! cant wait to see my GPU humming and spinning at full utilization!

    November 13th, 2017 at 22:09

  35. Ken Grady

    I have used Firefox for years also and have it on my Mac, is this new version available for Mac too?

    November 13th, 2017 at 22:22

    1. Grzegorz

      Yes. For Mac, Linux, BSD, Windows, etc.

      But Android and iOS don’t get the speedup yet. Android should get it later, while on iOS Firefox is forced to use Safari under the hood, so it’s always as fast or slow as Safari is.

      November 14th, 2017 at 04:36

  36. Wayne

    Been many years since I left the Mozilla fold having come up from Netscape (every version from 3.0 Gold onwards) through whatever version Firefox had six or so years ago. I’m interested but tentative as well. Tomorrow I’ll download the stable version and we’ll see where it takes me. Great write-up by the way.

    November 13th, 2017 at 22:38

  37. Chris

    Congrats to Mozilla! Over at my digital agency we all use, and love Firefox! Greatest browser ever, keep it up!!!!!!!

    November 13th, 2017 at 23:06

  38. Alper

    Thats great news. Keep up the good work. As an it pro, chrome is popular on everywhere because its easy to install even without admin previlliges on Windows.

    November 14th, 2017 at 00:21

  39. FDominicus

    Well I will come back if you make textfields at least fast enough to cope with my typing and by all means I’m a bad and not very fast typer.

    November 14th, 2017 at 00:25

  40. zoobab

    It’s 2017, and most programs stops at one core.

    Use ZeroMQ with IPC to coordinate your workers, and you can scale. No need to reinvent the wheel.

    November 14th, 2017 at 01:10

  41. aim

    Make Profiles as great as ‘Users’ in Chromium!

    Need a gui to simple switching between different Profiles
    Need a “Open as other user”
    Need no “firefox is already open” while opening external links while using different Profiles

    November 14th, 2017 at 01:43

  42. Dutra de Lacerda

    Better multi-CPU seems a way to go. But not the only.
    Focusing on it allows the trend of inefficient code to continue at will.

    Personally, I use old PCs to test any application.
    Right now using Midori on a 1GHz 686 CPU and 512MB RAM.
    What about JAVA? JAVA is to turn off, for several reasons.

    Cookies are not the only problem when consulting sites.
    Java, and the call to multiple locations not related, is a killer.
    Wonder why… We all know why: A tendency to abuse!

    All those must be blocked at will, call it as you will.
    … As well as ‘rendering’, where not needed.

    Shorter code is also a quality many abandoned.
    Wonder why… We all know why: A tendency to laziness.
    When Opera is no longer a 3Mb application…
    … Something is terribly wrong, and Lynx may be the way back.

    Everything tends to disruption… When abandoned to it.

    November 14th, 2017 at 02:22

  43. pushpendra

    Congratulations. I’m waiting for upgrade.

    November 14th, 2017 at 03:08

  44. Greg

    I’m going to try Quantum and as a long-time Firefox user I’d like to congratulate you all on what you’ve done.

    Unfortunately, the killing-off of support for the old add-on format in favor of WebExtensions is going to seriously throw off my workflow and kill off my productivity.

    (While some of this has changed since March, not enough has changed.)

    It will be some time before I am able to permanently switch to Quantum.

    November 14th, 2017 at 03:40

  45. Shazada

    I never jumped to any other browser :) and can’t wait to update tomorrow!

    November 14th, 2017 at 03:51

  46. Pablo Gonzalez Portela

    Thanks a lot, guys. I have been a firefox user since the very beginning and proud to stick with people that really vouch for the freedom of the user. I am so happy to see my browser blazing fast again! :)

    November 14th, 2017 at 04:32

  47. JiFish

    I’d rather have customisability than speed. That’s why I stuck with FF. Now that extensions have been massively nerfed, I am looking for a new browser.

    November 14th, 2017 at 04:47

  48. Gaz

    I have got my Firefox webbrowser customised exactly how I like it, but now most of those addons will be gone – all for the sake of speed. I loved Firefox for just how much I could customise just about anything I wanted on it.

    But now it will become just another Chrome clone.

    How far you have fallen!

    Ps. will we still be able to change the [background] themes/appearance? I use the Firefox Blue Dots theme everywhere.

    November 14th, 2017 at 05:39

  49. Kat Marsen

    Firefox is an old tired dog. It is sloooow. You can’t even type in a text field without it visibly hanging. If I have to use Firefox and have to type more than a single sentence, I’ll open up notepad, type the content there, and then paste it into Firefox, it’s that bad.

    And no, this isn’t some “custom plugins” deal: stock Firefox on fresh 48-core servers does it too (it’s the only browser installed on the machine).

    November 14th, 2017 at 05:51

  50. Carlos

    I am noticing issues when trying to open a minified JS file in the developer tools. The tab just says “loading…” and never loads. Perhaps this is not a common use case but from time to time I have to do some quick checks even on minified JS. This wasn’t a problem before.

    You can recreate on this very site by inspecting one of your JS files. Picked one just as an example (not really familiar with the contents not do I need to debug it :) but please take a look).

    November 14th, 2017 at 08:30

  51. Charley S

    Oh-mah-gawsh! I haven’t used Firefox in forever and decided to give Quantum a whirl: love. It. It’s fast, works well, and looks great.

    Keep up the fantastic work, it’s valued and greatly appreciated!

    November 14th, 2017 at 09:56

  52. MarkTheBike

    Unlike others, I didn’t forsake FF for Chrome (Chrome is Google, Google is poisonous IMHO). I use FF wherever possible and have donated (too long ago, I’m embarrassed to say). Thank you, guys, for your hard work and determination to keep FF alive for those of us who object to being seen as ‘The Product’. ps. All my Add-Ons appear to have been updated, hooray!

    November 14th, 2017 at 11:01

  53. Jigar

    $ ps aux | grep -i ‘firefox’ | wc -l

    Awesome work team!

    November 14th, 2017 at 11:17

  54. Pär Amsen

    Just tried v57.. hats off! I’ve switched to FF on all my desktops now, fast, beautiful and awesome!

    November 14th, 2017 at 11:27

  55. lje

    bravo and thank you for the good job.
    i had many troubles with 56. no more now.
    very fast, with privacy badger and ublock.
    i like the fluent scrolling !

    November 14th, 2017 at 12:07

  56. FatTony

    great article. easy to understand and very entertainingly written. thank you!

    November 14th, 2017 at 15:50

  57. Dhruva

    Good article with enough technical depth covering various aspects of the browser. Having to plumb an existing code base to bring in all the changes to work well with modern hardware is a herculean task. Well done and all the best.
    The task stealing part reminded me of my work using Intel Threading Building Blocks (https://www.threadingbuildingblocks.org/) back in 2007/08 – Recursive parallelism

    November 14th, 2017 at 20:53

  58. Stefan

    Congratulations for the new Firefox! And a big “thank you” for the hard work!

    I am just a bit worried because of “old” add-ons. This is the most important unique selling point of Firefox, aside from privacy and open source.
    For example: There seems to be not auto-delete for LocalStorage, including a whitelist. All add-ons for this scenario are not working anymore. Developers told me, there is no access to LocalStorage anymore for add-ons.

    Thats why we will stick with FirefoxESR until this is solved. And I hope it CAN be solved. Some developers of add-ons told me, that there is no way anymore because of restrictions. I am not a developer, so I just have to believe what I have heard.

    Anyway, it looks like Firefox is on a good way! And if the necessary add-ons for improved workflow (search bar) and privacy (LocalStorage, for example) will work again, our company will make the move from ESR back to “normal” Firefox!

    All the best, and thank you again for your hard work!

    November 15th, 2017 at 05:07

  59. Patrick Sullivan

    Firefox ran the best for the longest time. Now when first downloaded it runs great for about 30 minutes, then it picks something up.

    “A script is running on this page, do you want to stop it?” One reads.

    Another read:

    “A web page is slowing down your browser.”

    Once it picks up whatever it is, it runs slow?

    Any suggestions as to what could be coming in after about 30 minutes of browsing?

    November 15th, 2017 at 11:16

  60. Rafael Ebron

    Nice job and good explanation/article! Nightly builds are good.

    Keep up the good work. Always celebrate releases.

    November 15th, 2017 at 11:18

  61. Big Pete

    Updated at home and its pulling me back from Chrome. Were using ESR at work (updte cycles) so do we have to wait til ESR 59 for the QuantumESR?

    November 16th, 2017 at 05:33

    1. Lin Clark

      Yes, the first ESR release to include everything from 57 will be ESR 59.

      November 16th, 2017 at 05:54

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