Mozilla Firefox 139.0.1 includes a crucial fix for an irritating bug that caused artifacts with Nvidia GPUs in certain setups. This bug was introduced with version 139.0, likely because Mozilla disabled a blocklist that prevented DirectComposition from being used with Nvidia GPUs, and multi monitor setups with different refresh rates.
Mozilla launched Firefox 139.0 on May 27th, introducing a slew of new features, such as custom new tab backgrounds, full-page translation for supported extensions, just to name a few. However, shortly after the update went live, forums and Reddit threads were teeming with user complaints of graphical anomalies, glitches, and screen corruption. Essentially, if 60 FPS media is running on the secondary monitor, interacting with the primary high-refresh rate display can induce visual artifacts.
As it turns out, Mozilla removed a blocklist that had previously prevented DirectComposition from being used on certain Nvidia setups, specifically referring to multi-monitor configurations with mixed refresh rates, say 144 Hz and 60 Hz. A workaround for the bug was discovered by several users at Bugzilla, which involved toggling the gfx.webrender.dcomp-video-hw-overlay-win flag to false.
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It's not entirely clear why Mozilla suddenly removed this specific blocklist. A Mozilla developer indicated that Firefox handles graphical buffers differently from other browsers, using "Surfaces" instead of "Swapchains" with Windows DirectComposition. They also hinted at a new Layer Compositor, which affects the way elements are drawn on your screen, aiming to mimic other browsers more closely. This shift could be the reason the blocklist was initially removed, but it's hard to be certain.
This problem shouldn't affect users with Intel or AMD graphics, or those with single-monitor setups. Firefox 139.0.1 solely targets this issue, so don't expect other fixes or new features. That being said, to address this, you can either manually disable the flag or update your browser by navigating to the menu button (three horizontal lines) at the top-right, then selecting Help, and About Firefox. Firefox will automatically check for updates and download them if any are available.
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