Speaking of Firefox performance, does anyone know what introduces pauses in page loading? A page of 900 bytes HTML, with 2 KB of CSS and a 33 KB background image, takes 918 ms to load. Only a third of that is network stuff (DNS resolving, TLS setup, etc.; adding up the 'duration' values). Screenshot of page with loading graph: https://i.snipboard.io/AcqWb4.jpg Notice the huge gap between HTML loaded and starting to load CSS, for example, where it does not appear to be doing or waiting for anything.
Seeing the title and initially glancing at the drawing where it says "reading XUL.dll" I thought they addressed this, as I noticed this problem a while ago and I figured it was something about this multi-process browser experience having to load everything anew or constantly do inter-process communication, but the post is actually about various other performance issues. Does anyone know what's up with this one?
Just to be clear, I'm not saying Firefox is slower than browser X or anything. I just happen to notice this in Firefox because I'm a Firefox user.
Thank you a lot! I just tested it on my Android phone and finally I don't have to wait seconds before I see any page content. I was really puzzled what caused this problem for a while.
Oh wow, this is more than a performance problem, this is a mitigation for a data security problem that only got introduced because trackers try to work around per-domain cookie isolation.
It can literally tell you what can go wrong inside the whole Firefox architecture (Includes network, webtension, firefox internals, page scripts and so on).
My personal guess about it is about extensions, did you retry it again in safe mode?
And if you suspect it is a issue in firefox itself, you can upload the profile and open a bug at https://bugzilla.mozilla.org/home , so someone more familiar with Firefox can investigate it.
Good point, should have thought of that. I have a bunch of things open where I don't want to reload the page so restarting in safe mode is a bit tricky now, but unless someone happens to know the exact answer I can try this on the weekend and perhaps narrow it down, thanks :)
Some issues are caused by the current profile, so it is a good idea to use a temporary profile for testing weird bugs. Here is a script to automatically create and clean up a temporary Firefox profile:
The really interesting part is the huge gap between loading the CSS and starting the load of "patternbg.png", which is linked to by the CSS. When I load https://lgms.nl/ locally, I see the CSS finish loading at the 397ms mark in the overall pageload and the image load get queues at the 411ms mark, which is more like what I expected.
My best guess is that there is some extension involved that takes a long time to process attempted fetches and decide whether to allow them or not.... It would be interesting if the timeline included "we are ready to go fetch this and waiting on extensions to make up their mind" bits.
Which OS is that on? Mine was on Linux, perhaps that makes a difference. Also I have a rather crappy cpu (i5-8250U); for you I still see the gaps even if they're smaller (both in absolute terms but if I'm seeing it correctly also in proportion to network loading time), so perhaps a faster cpu helps as well.
I super excited for any new FF stuff but this one mentions a lot of Windows focused (and some Mobile) - I'm over here on Linux where I've still got loads of pages that just lag. Hoping for some multi-platform JS updated soon-ish.
Side note: anyone know of any meaningful updates to Servo? Is dead? It had so much promise (IMO)
Servo was never meant to be a full engine replacement for mainline Firefox; whatever Rust code could be implemented/useful for Firefox was ported already.
However, regarding Servo specifically, there are contributions on their GitHub[1] and the stewardship of the project is now under the Linux Foundation[2].
> Servo was never meant to be a full engine replacement for mainline Firefox
I don't think that's a fair summary of the history. There were multiple points of view on this inside Mozilla, and some (including myself) definitely hoped it would be a full engine replacement.
Really? Bummer. I hope the community keep a steady pace at development and don't let it die. Having another engine competing with the "titans" of the current web would bring so much benefit (I think and hope so).
The "recent" event[0] with Chrome dev team scared me; they have so much power to change things "at will".
I'm not sure when it happened, but in the past few months I started noticing slower responsiveness in Chrome. Which is weird, because historically that was the type of thing I tolerated in Firefox.
It looks like Firefox is the new speed champ on MacOS, at least among serious browsers. If Safari's WebExtension ecosystem actually progresses with Safari 15, that may be worth another shot, too.
It's definitely not slow on macOS but for some reason the UI font just looks wrong to me on macOS and I can't quite put my finger on it.
The font doesn't look system (maybe it is), and every element is a tad too small. Spacing between letters is also more cramped that on every other macOS app.
I know doing cross OS development is hard but to me this is what's stopping me to move full time from Safari to Firefox on mac, the UI font just looks wrong (despite all the things I don't like in Safari like not having uBlock Origin and having to rely on a subpar extension with an app, or the terrible new Monterey UI).
My gripe with FF on Mac is the lack of support for autocorrect. While I can live without autocorrect, this also means my text expansions (stuff like shrug -> ¯\_(ツ)_/¯) don't work in FF but work in basically any other text bo, since they use the same text replacement mechanism.
I have the opposite behavior on my macbook pro - Chrome can handle videos at 2x speed just fine, but Firefox will stutter or go sound-only for a few seconds if it heats up at all.
Video handle really varies depending on how it was encoded and whether there is a hardware decoder available or not. YouTube is highly tuned to work well with Chrome and vis versa.
These are some good changes. Perceived performance is very important for a program you use many times per day. One of my long time complaints is that with Chrome, when I want to search for something I'll often ctrl-N to open a new window and then type my query. Even if it takes a little bit of time to show the window my query will be right there in the search bar. With Firefox, those keystrokes are lost. I hope this fixes that.
For as long as I can remember, Firefox has always been janky and slower than Chrome at moving tabs in and out of windows.
Dragging a tab doesn't always create a new window, sometimes it acts as bookmarking if I drag it into the tab bar, sometimes (on Linux) it acts as drag-dropping the tab into another app like Discord and fails to open a window.
Dragging a tab out of a window doesn't create a new window until you release the mouse, so it feels unresponsive, and you don't know whether you'll get a bookmark or tab or nothing at all. And dragging the last tab out of an empty window doesn't close the window to allow me to see what windows lie underneath.
And in the past (not sure now) I've noticed that dragging a tab a few pixels downwards would create a new window, when I meant to click or reorder a tab.
> And in the past (not sure now) I've noticed that dragging a tab a few pixels downwards would create a new window, when I meant to click or reorder a tab.
I've had this problem for a long time as well; it's very hard to reliably reproduce too. I ended up finding some about:config setting to just disable this entire feature, and my life has been better since.
When I was reading this, and the author mentioned XUL.dll taking a long time to load I was assuming the blog would veer into a discussion about what can be done to refactor that code to make XUL.dll smaller. Can it be broken into separate DLLs, with the core portions loaded first? Is there a better design that could be used? But, no, their solution was to show the windows soonest. That's nice, I guess, but it didn't solve the problem. It just solved the user's perception of the problem. It actually increases the load time, so now you have an unusable window for a longer period of time. That's one of my pet peeves - don't give me an interface until you're ready for me to start clicking on things.
XUL is the name of Mozilla's old UI language [1]. They've been in the long process of moving UI pieces from XUL into HTML5 (such that the Browser's UI controls use the same renderer as the Browser's contents). One key piece of that was disabling the ability for extensions to use XUL a while back that caused a lot of churn in Firefox extensions.
The impression from that is that they want to entirely get rid of XUL.dll at some point in the future.
I'm the opposite of someone who keeps tons of tabs open, I'm constantly closing and reopening the browser through out the day. One of main reasons why I started using Chrome in the first place all of those years ago was the start up speed. I know Firefox is much better today at this in the past but any improvement would help me switch full time to FireFox.
I turn my computer off frequently and FF launches instantly when I open it. Just as fast as any other program (and I'm a tab hoarder).
Though the number one reason I have FF instead of Chrome is that FF Mobile allows ad blocking. So I can have ad blocking across my browsers, send tabs, and keep consistent plugins. The anti-tracking and privacy features are also a great plus.
That is precisely the reason I switched back to Firefox after all those Chrome years.
The Firefox startup is pretty much instant. Chrome starts fast as well, but there is a moment, when it's just a blank window that I can't do anything with.
Firefox opens instantly to a usable window with the cursor blinking on the address bar.
I switched back to Firefox from Chrome a few years ago after their Quantum efforts landed. Both to get out of the Google trap, and because it was clearly the fastest browser for common use, except on certain Javascript heavy pages.
But over the last year or so, performance has continually degraded to the point were I'm upset and resort to Chrome more often (Ungoogled Chromium [1], to be precise).
I guess Specter mitigations and site process isolation might be related, but this does not make me happy...
Since I switched to Firefox I have to restart it every 3 days as it gets slow. All debugging suggestions start with "disable all plugins." But this is not practical. We practically live in our browsers nowadays. Without my ad blocker, password manager, and grammar checker I will be severely handicaped. I wish there is a way to debug the situation without resorting to disabling plugins. Perhaps have access to some per-plugin metrics.
For me that seems to be new behavior. I used to be able to keep it open for weeks without issue, but within the past month or two I've started having to restart it all the time (MacOS).
I wish Mozilla spent ten percent as much time un-fucking their old features as they do coming up with new ones. Firefox Mobile still doesn't have a user agent switcher. The "tab closed" popup still blocks you from opening the next tab. There's still no option for moving the New Tab button to the top of the screen.
More importantly, you can't read long text in small copy by zooming in without having to scroll sideways in FF mobile. That's just such an obvious UX problem it's unfathomable how it hasn't been addressed yet. There's been an issue open on this problem for about 10 years already.
Yeah, wrap the text to the viewport. It's what Opera does and it's perfect to me, as I have trouble reading small font sizes, so I got used to just zooming the heck out of text.
I get the same kind of fascination reading those comment threads as one would get watching a train wreck. To multiple users telling them that their stuff is broken, they reply that this is their actual intent. The thought that maybe there might be a flaw in their design does not cross their minds an instant. "Am I out of touch? No, it is the users who are wrong."
I particularly love the suggestion to use https://ideas.mozilla.org/ to submit feedback, as if that change went through the same procedure, and as if they didn't moderate away any suggestion that they don't like.
And yet they still don't realize that this "we know better than the users what's good for them" attitude is killing their product.
> multiple users telling them that their stuff is broken
You can find multiple people who would describe anything as broken. I'm several dozen comments into that thread and I still haven't found a single person even attempting to explain why the old functionality is needed beyond "I don't like using my `?` and `Ctrl-K` keys", which Mozilla absolutely should not have dignified with as much time as they gave it.
The person arguing that the entire search box should just be removed if it isn't actually any new functionality has a point, but that's somewhat tangential to the "bug" they're describing.
People have been using this for years; they're used to it, it's in their muscle memory. People really don't like it if stuff like that suddenly changes. I think that's reasonable and normal.
Whether using ^K or ? is better or worse is entirely besides the point.
> People really don't like it if stuff like that suddenly changes. I think that's reasonable and normal.
Normal yes, reasonable no. It's a problem that solves itself extremely quickly if you just learn to accept it. It's mildly annoying for a few days and that's it. Sure, let's not go breaking muscle memory willy-nilly just for the sake of it, but you can also go too far in the other direction: https://xkcd.com/1172/
In this case there's no downside at all beyond "I hate change", and opening a bug report is way more effort than just getting used to that.
They've been chasing Chrome's market share for so long they forgot the reasons they ever gained market share in the first place. Except nowadays with a 3.5% market share it's less "chasing Chrome" and more "dragging their balls through a mile of broken glass to hear Chrome fart through a walkie-talkie."
They could've kept ten percent forever if they didn't forsake the things that made Firefox great in the first place and the people who loved them for it. Now they've thrown that away and along with it any chance to avoid irrelevancy and extinction.
It's not a bad change as such, the motivation seems sensible. Although it does seem like a bit of a minor issue, and also a rather weird/confusing way to solve it.
I think the main problem is that Mozilla consistently underestimates just how much people hate it when their software changes behaviour in surprising ways, and also how little control they give to users over these kind of changes.
Yeah, I agree. I also didn't know about this, the popup didn't convey the idea of "dismissible"... I learned about this reading a rant on Reddit about the UI.
Maybe it's different on nightly but for me the closed tab notification does not block anything.
I can't speak for putting the new tab button to the top, but I was asked if I want the URL bar at the bottom or top when installing Firefox for the first time. For me having the controls at the bottom is one of the killer features, because I can just use my thumb to do things.
Not fully. It requests a desktop layout but sites still know you're on a mobile browser, hence sites that explicitly block mobile browsers will show the same "this page only viewable on desktop" message. Actual user agent switcher extensions don't have that problem.
It does change but it only removes the "mobile" part from user agent (through sniffing). But I think he's referring to a broader usage, for instance: MS Teams only works on Chromium-based browsers and Safari, so user agent change façade comes in handy for this.
Tbh as much as I'd like a user agent switcher I really like the new stuff too since a lot of it is aimed at convenience out usability. Blemishes aside it's quickly become my favorite mobile browser to use (having already tried Chrome, Edge, Brave, and a few others.
In my experience it could be 5 minutes could be an hour. Pretty much guaranteed after the phone being locked for 30mins+
I have the following add-ons installed: Decentraleyes, HTTPS Everywhere, Privacy badger, and uBlock Origin.
Running a Nokia 6.1 for reference. Not super powerful, reasonably old, but not bottom of the barrel.
I have tried disabling all add-ons but I still get the bug as described.
Which reminds me of my second gripe, having tabs refresh after switching apps then back to FF. Super frustrating, especially if it's a login flow or filling in a form.
Yes! When attempting to close the last two tabs in the vertical tab list, one after another, the "Tab Closed ↩" popup of whichever tab you close first will arise at the bottom of the list and obstruct the close button ('X') of the remaining tab, for it's full 3 second duration. Hence, to close the last n tabs, you must close the second-to-last tab n - 1 times, and then wait those 3 seconds to close the last tab.
Ok I now understand what someone earlier was talking about. This is fixed in nightly, because the have a new open tabs representation. Also you can swipe the notification away, and you can close the tabs by swiping also (I'm never using those small close buttons).
I just checked this in nightly and the problem persists. Open at least ten tabs, set tab view to list instead of thumbnails, close a tab using the X on the right, try to select the latest tab (the one at the bottom). You can't because there's a helpful little "tab closed" notification.
> Previously, when a Firefox user encountered a page that had a script that ran over a certain timing threshold, you would see a warning message that looked as follows:
I'd appreciate if the "Stop It" button actually worked, instead of the page and JS engine remaining hung for several seconds afterwards.
If you open an application when it's already open, Windows creates a whole new instance of the application instead of just switching to the already-open application.
> If you open an application when it's already open, Windows creates a whole new instance of the application instead of just switching to the already-open application.
This can be handled by the application though. VLC for example has an option ("Allow only one instance") so that it will only let you, uh, open one instance at a time - if you try to open VLC again while there's a Window already open it just (IIRC) sets focus to the existing window.
I think Firefox opening a new window is an intentional design decision.
I don't think that's what's going on here. I'm pretty sure they're measuring the performance of the first window opened. A lot of Windows applications, Firefox included, do single-instance manually by opening an IPC connection to the old instance and telling it to open a new window. Also, DLLs in Windows are only loaded from disk into memory once. If XUL.dll is already in memory from another instance of the application, it won't be read from disk again. (It won't even get rebased for ASLR again.)
Kind of baffling to hear multiple application instances described as "weird," though. I guess that might be the case from a Mac perspective. Having a separate process per application window is fairly standard in Windows and desktop Linux. It gives you a simpler programming model, since per-window things can be global or singletons, and you can always terminate the process when the user presses the close button, rather than having to check for other windows. It also makes you more robust to application crashes, since only one window will crash.
And what if you don’t want the process to close? What if you want to open a new window after closing the others? On Windows you have to wait for the whole app to start up again.
That's another thing I'd argue is "weird" in macOS, the only widely used modern desktop operating system that does things this way, rather than vice-versa. Most new converts from Windows or desktop Linux to macOS tend to accidentally leave apps open because of this, since the only indication they're open is a tiny dot in the dock, and most of the time, the only remaining UI once everything is gone is a menubar. For an otherwise document-oriented UI, the fact that an application can be open with no documents is a strange concept that requires some getting used to.
Over the past iterations of Firefox (mobile), especially since they launched their new UI, I've noticed the performance of features such as CSS animations, etc. have particularly degraded. I have two versions on my Moto X4, Firefox 68 and the new Firefox 92. I use both to test some of the web apps I develop and to my surprise the older version of Firefox performs much better! There's a noticeable jank on the web app (transitions, animations, etc.) on the newer version. The browser itself is much slower than the older Firefox 68.
Frankly I don't see any performance improvement.
for some reason I thought XUL was dead and gone, with the UI now coded in html and js - wonder if they can further improve loading by removing XUL in the futre
I don't know if it is related to this article, but a month or two ago, I found screen sharing with WebRTC (specifically getDisplayMedia) on Firefox have been suddenly notably improved. I read through release notes at that time but there seemed no changes around it, except improvements for WebRender on Linux (whereas I and my colleague use FF on Mac).
If one of the contributors named in the article involved in it, I appreciate greatly since it significantly improved our remote-work environment.
Meanwhile I feel like on my Linux laptop Firefox has only been getting slower and slower every year. Perhaps the fact that I'm using a GeForce as my primary GPU can have something to do with it? I read it causes some problems with WebRender. Anyway it's sad to see Chromium being way snappier on my machine, I have to use it for meetings because just after a couple minutes audio in FF starts to stutter intolerably.
Some time ago I removed a whole bunch of packages from my system I hadn't used in a long while, and turned out I also accidentally removed the "pciutils" package which turns out to be a runtime dependency for Firefox's hardware support.
Without it, regular things were significantly slower, especially if images were involved, even on simpler sites. Just installing pciutils again instantly made a huge difference.
wish they would let users completely disable checking for updates. and get rid of only allowing 'signed' extensions. my guess is that will never ever happen
I remember years ago when Firefox Quantum boasted of lofty performance improvements only to get pummelled in just about every benchmark against Chrome. I still check out Phoronix's benchmarks now and again and Firefox is consistently behind. Make whatever excuses you will, but the numbers don't lie.
I'll gladly suffer a little bit worse rendering performance and have images resized with good rescaling filters than the blurry pixelated mess that Chrome renders whenever the zoom isn't exactly 100%. It's easy to do well on benchmarks when you sacrifice rendering quality.
And of course there's no way to even ask Chrome to render images with a decent resampling filter...
I use highly interactive websites, like bitcoin exchanges.
They work terribly in Firefox. I don't know if it's because Firefox is slow, or if because devs don't test in Firefox. Either way, even if Firefox is my main browser, I learned that I need to use these sites only in Chrome.
YouTube and most other video sites also are very slow in Firefox and many times the other sites don't work at all, video doesn't start, ...
This came up a few days ago as well, I and many other people have zero problems with YouTube on Firefox. So dunno why some people report that it's atrociously slow.
I'm not sure if benchmarks reflect real-world performance with adblockers and other extensions installed. I've been using FF (nightly) as my daily driver on Linux and Mac for years and I don't see any perceptible difference in page loading times compared to Chrome. The only area where I find Chrome noticeably faster is in starting the application itself, but since I rarely close the browser this is not something I see often.
Unfortunately corporates seem to be ignoring Firefox entirely - last 2 companies I worked at, their webapp worked only in Chrome. So I'm forced to use Chrome (or Chrome-ish browsers like Brave) also on a daily basis.
The first one is embarrassingly stupid. The real solution is a splash screen, which was invented decades ago. Instead, they just lie to you with a non-functional window rather than lying to you by pretending that your system is doing nothing.
Moved back to Chrome today btw. Couldn’t handle YouTube full screen taking 10 seconds to expand and collapse on Firefox. Sure wish Mozilla would hire some competent devs.
You're kidding me! Splash screens are the worst solution for this (actually for anything).
1. They often sit on top of everything so I can't continue working on another document for example when opening a large application (I often open apps but continue working on something else)
2. The mess up window management, because the don't have the window class and name of the main app. So when I set window management rules, I have to set an additional on just for the splash screen (made more difficult because it's only there temporarily).
3. The only information they provide is that the app is starting. Well yes I just opened it. Better show an empty window, at least that avoids 1 and 2.
>Moved back to Chrome today btw. Couldn’t handle YouTube full screen taking 10 seconds to expand and collapse on Firefox. Sure wish Mozilla would hire some competent devs.
Right, don't blame Google that purposefully slows down Firefox on half their websites.
It's not a bad trick, as it presents you the UI. It will take you a bit to actually respond to the change of the window opening and moving your mouse or whatnot to do whatever you want to do, and this "human delay" time can be used for Firefox to load fully.
Slash screens, on the other hand, are basically just useless and don't add anything beyond an indication of "the app is loading", but the hourglass mouse cursor (or whatever it is on Windows these days) tells you that already.
Seeing the title and initially glancing at the drawing where it says "reading XUL.dll" I thought they addressed this, as I noticed this problem a while ago and I figured it was something about this multi-process browser experience having to load everything anew or constantly do inter-process communication, but the post is actually about various other performance issues. Does anyone know what's up with this one?
Just to be clear, I'm not saying Firefox is slower than browser X or anything. I just happen to notice this in Firefox because I'm a Firefox user.