Challenge: Snitch on the glitch! Help the Graphics team track down an interesting WebRender bug…

For the past little while, we have been tracking some interesting WebRender bugs that people are reporting in release. Despite best efforts, we have been unable to determine clear steps to reproduce these issues and have been unable to find a fix for them. Today we are announcing a special challenge to the community – help us track down steps to reproduce (a.k.a STR) for this bug and you will win some special, limited edition Firefox Graphics team swag! Read on for more details if you are interested in participating.

What we know so far about the bug:

Late last year we started seeing reports of random UI glitching bugs that people were seeing in release. You can check out some of the reports on Bugzilla. Here is what we know so far about this bug:

  • At seemingly random intervals, either two things seem to happen:
Black boxes!
  • The majority of the reports we have seen so far have come from people using NVIDIA graphics cards, although we have seen reports come in of this happening on Intel and AMD as well. That could be though because the majority of the people we have officially shipped WR to in release are on NVIDIA cards.
  • There doesn’t seem to be one clear driver version correlated to this bug, so we are not sure if it is a driver bug.
  • All reporters so far have been using Windows 10
  • No one who has reported the bug thus far has been able to determine clear and consistent STR, and no one on the Graphics team has found a way to reproduce it either. We all use WebRender daily and none of us have encountered the bug.

How can you help?

Without having a way to reliably reproduce this bug, we are at a loss on how to solve it. So we decided to hold a challenge to engage the community further to help us understand this bug better. If you are interested in helping us get to the root of this tricky bug, please do the following:

  • Download Firefox Nightly (if you don’t already use it)
  • Ideally you are using Windows 10 (but if you see this bug on other platforms, we are interested in hearing about it!)
  • Ensure WebRender is enabled
    • Go to about:config and set gfx.webrender.all to true, then restart your browser
  • If you encounter the bug, help us by filing a bug in Bugzilla with the following details:
    • What website are you on when the bug happens?
    • Does it seem to happen when specific actions are taken?
    • How frequently does the bug happen and can you ‘make’ it happen?
    • Attach the contents of your about:support as a text file
  • The main thing we really need are consistent steps that result in the bug showing up. We will send some limited edition Graphics swag to the first 3 bug reporters who can give us consistent STR!

Even if you can’t easily find STR, we are still interested in hearing about whether you see this bug!

Challenge guidelines

The winners of this challenge will be chosen based on the following criteria:

  • The bug report contains clear and repeatable steps to make the bug happen
    • This can include things like having a specific hardware configuration, using certain add ons and browsing certain sites – literally anything as long as it can reliably and consistently cause the bug to appear
    • BONUS: A member of the Graphics team can follow your steps and can also make the bug appear
  • We will choose the first 3 reporters who can meet this criteria (we say 3 because it is possible there is more than one bug and more than one way to reproduce it)
  • Winners will receive special limited edition Graphics Team swag! (t-shirt and stickers)

Update: we have created the channel on Matrix so you can ask questions/chat with us there. For more info about how to joing Matrix, check out:


23 thoughts on “Challenge: Snitch on the glitch! Help the Graphics team track down an interesting WebRender bug…

  1. New reddit (old one is OK). Webrender doesn’t like that site one bit. Just a few minutes of scrolling is enough to elicit a ton of bugs. Jumping text, black boxes, stuck scrolling (usually mid some image/video frame) that takes several seconds to unstuck while the bottom of the content area is shimmering from side to side (similar to tearing artifacts) etc. Happening on two separate systems with an AMD RX570 and Intel HD. I have went through several drivers on both, so I don’t think it’s driver dependent.

      1. about your buggiw, I have noticed something simular (boxes that appear then go away) and it reminds me of advertizing tiled spam adds boxes that my security software is suspposed to block, and does after a few moments…
        My web provider is Cox Cable which provides McAfee…
        Your main Firefox problem is that the text on many websites made in Chrome or ? is faded and hard to see….. as well as some websites site editors cannot be updated using Firefox, only using Chrome….
        I tried to tell your corporate but they ignored me…thanks, Lewis

  2. Yeah, I’ve seen this bug lots of times. Windows 10, NVidia graphics as with the other reports. Don’t have a solid repro, but my feeling is Instagram triggers it most often. Funny thing is it blacks out the chrome (i.e. the tabs at tht top of the window) as well as the actual browser tab content. As soon as I click in the Window it redraws.

  3. I see something else: A white screen occasionally on first load of the tab, on windows 32 bit at work, and on my android phone.

  4. I enabled WebRender, opened Reddit, scrolled furiously… And my PC completely locked up. Page rendering was just fine, though.

  5. I encounter this glitch many times, normally a few times per week. The text on a page will suddenly appear distorted like the code in the movie the matrix. Running W10 on dual DVI monitor setup with NVidia GeForce GTX 1050 Ti on an AMD Ryzen CPU. This glitch has occurred to me on both developer & stable channels but I will start daily driving nightly to try to figure out if I can reliably come up with STR.

    General observations on when it is occurring to me are below:

    I have a number of tabs open in a browser session that has been opened for at least an hour – it will occur sporadically when I navigate over to a tab opened in background. When I mouse wheel down the glitch will “repair” itself and the page will render fine. Sometimes the glitch will be on all tabs if i move between them without using mouse wheel down on a page to “repair” the glitch.

    I can try to screen capture the next time it occurs if that could be at all helpful.

  6. Not just on Windows 10, I’m on Ubuntu and I have this bug (black boxes). I do use a Nvidia card. It happens on one of the sites I develop. I’ll try to isolate the bug.

  7. On Ubuntu 19.10 with NVIDIA proprietary drivers it happens every time after resume. But WebRender is not officially supported on Linux. Should I open a bug ?

    1. Same. Ubuntu 19.10 on Thinkpad T490 (intel) laptop with external NVIDIA GPU. After suspense (until I move the mouse) the tabs of tree style tabs (only the tabs) have colorful glitches kind of like colored strokes. Will try to make a screenshot the next time it happens.

  8. I have had this happen on Linux (archlinux build), with an AMD card (RX 580), kernel drivers. It is somewhat rare, I see it about once or twice every week. It has been happening for at least a month now, on stable versions, with the new renderer enabled. No idea how to reproduce it reliably.

  9. FWIW, I’ve seen it before here (Windows 10 amd64, Intel HD4000 with latest driver) and it seems to either not show up in periods (I wish I could determine cause…) of not showing and constantly showing. The complexity of a page doesn’t seem to matter; very simple little-to-no-JS websites like Wikipedia and Lobsters can trigger it. I’ve also seen some very odd text rendering bugs from it as well, such as smeared or stretched text, or failing to use the same font.

  10. Both mentioned artifacts happened to me, although rarely.
    And yes, they seem to be *very* random, I haven’t found any pattern to them.

    Win10, RTX 2070, Ryzen 2700X here, on the stable FF channel.

    I do have *very* long running sessions. I basically never close FF, and I suspend/resume Windows for weeks, until it forces a restart on me. I do have all kinds of games etc running in the background, tabbing between everything, the usual.

    Since this problem randomly appears, and then randomly disappears as well, I haven’t really payed much attention to it, but as I remember, just tabbing / hovering was causing this, and scrolling / selecting text can make it go away.

  11. I’m posting this here, as one of the type of the glitches is exactly what you show on the snapshot.

    After Firefox updated to v73.0.1,
    I tried to check how things are with gfx.webrender.all ON

    After starting seeing glitchy video, I turned it back OFF… and restarted FF.
    Glitches continued !

    While a video preview was showing (on FB), moving the mouse over the like button, popped up a selection of the “like options” – this made Firefox hanged for 30 seconds, and glitches become very bad after that.

    I manually turn OFF any and all features of webrender (as it turns out some are enabled by default).

    Glitches continued and gradually things got even worse!

    I started seeing frames in the video previews from different videos.. and things got again worse.

    I started getting elements of one tab drawn on place of elements on a different tab (scaled to fit).
    (including the glitches you show here, also styling errors – like stretching resizing of content)

    At this point I started looking into the procedure of rolling back the update, which happened to be almost impossible ( v72 was refusing to load my profile as it was done with v73 to protect me from losing data… so it was not really possible to rollback… so “thanks” for that).

    I managed to download v73 again, installed it, copied the old profile back, and finally got back to where I started.

    Went into NVIDIA panel, and set “Program Settings” for Firefox.exe to be rendered with integrated graphics. Now there are no glitches, things work fine.

    OS: win / NVIDIA driver: 425.31

  12. I see this happen often, however I cannot post any specifics because it’s an internal website at our company – I guess not being able to post a link to verify it on your end kind of misses the point ;) I can give some specifics, though. Mainly, the website we use is using… flash on its login page (it will be replaced with pure html5 soon ;)). Minimizing the browser and then maximizing again causes the effects described in this post. Resizing the browser window removes the artifacts. All PCs are running Windows 10 and an Intel integrated graphics (Haswell generation and up). I am not sure if it has happened on AMD based systems. Not sure if it has any importance, but the PCs also run Google Chrome simultaneously (for reasons unknown, possibly users’ preference).

    I did not see this issue on any of my personal computers or on any other website on the company PCs, but the one address I cannot give a link to ;) I’m not sure if Flash is the direct cause on our end, but maybe its implementation in Firefox shares some code with other areas and my post may point you in the right direction. Most probably not, though ;)

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