Firefox 121.0.1 WebGL 'NS_ERROR_ILLEGAL_VALUE' on Intel GPUs: Fixed

You're mid-game or fiddling with a 3D web app, and suddenly the tab goes blank. You open the console and see NS_ERROR_ILLEGAL_VALUE—WebGL context lost. This hit me right after an Intel driver update on a Dell Latitude with an Intel UHD 620. Firefox 121.0.1, Windows 10. One minute everything's fine, next minute nothing renders.

Why this happens

Intel's newer graphics drivers (around versions 30.0.101.3113 and later) changed how they report texture limits. Firefox's WebGL code checks those limits and gets a value it doesn't expect—hence the 'illegal value' error. The context dies, and you're stuck with a blank canvas. It's not your fault, and it's not Firefox's fault either. It's a driver handshake gone wrong.

The fix that actually works

You have two solid paths. Try the first one first—it's faster and doesn't touch your system drivers.

Option 1: Turn off hardware acceleration (2 minutes)

1. Open Firefox and go to Settings (type about:preferences in the address bar).
2. Scroll down to Performance.
3. Uncheck Use recommended performance settings.
4. Then uncheck Use hardware acceleration when available.
5. Restart Firefox.

That forces Firefox to use software rendering for WebGL (via SwiftShader). It's a bit slower for heavy 3D, but it's stable. If you're just viewing maps or basic WebGL demos, you won't notice the difference.

Option 2: Roll back the Intel driver (10 minutes)

If you need the GPU acceleration for games or complex 3D apps, rolling back the driver is the better route. Here's how:

1. Press Win + X and select Device Manager.
2. Expand Display adapters, right-click your Intel GPU, and choose Properties.
3. Go to the Driver tab and click Roll Back Driver.
4. If it's grayed out, download the previous driver from Intel's site or your laptop manufacturer's support page. For example, Dell has older versions in their driver library.
5. Install it, restart, and test Firefox.

I've seen the rollback work on several machines, including that Latitude. The older driver (pre-November 2023) doesn't trip the WebGL check.

Still broken? Try these

If neither fix works, you're dealing with something else. Here's what I'd check next:

• Firefox's internal WebGL settings. Type about:config in the address bar, search for webgl.disabled, and make sure it's false. Also check webgl.force-enabled—set it to true if it's false. Sometimes an earlier tweak left it off.
• Try a fresh profile. Close Firefox, press Win + R, type firefox -P, create a new profile, and test. If it works, your old profile has corrupted settings.
• Check for other GPU drivers. A leftover NVIDIA or AMD driver can conflict. Use Display Driver Uninstaller (DDU) in safe mode to clean out old drivers, then reinstall only the Intel one.

One more thing: some corporate laptops force driver updates via policy, so rolling back might not stick. In that case, the hardware acceleration toggle is your only friend until Intel patches it.

The good news is this isn't a hardware failure. Your GPU is fine. It's a compatibility hiccup that's already been acknowledged in Firefox bug reports. The fix is either making Firefox ignore the driver's bad values or using the driver version that didn't have them.

Try the software rendering route first. If you're not a hardcore 3D user, you won't miss the acceleration. And if you are, the driver rollback gets you back to normal. Either way, you'll be back to your WebGL apps without that annoying error.