Chrome WebGL software fallback not being used

Question

Originally posted here.

I was under the impression that WebGL should work on Chrome on pretty much any desktop device, but that it may fall back to software rendering in some cases (assuming you don't pass failIfMajorPerformanceCaveat=true when getting the context). However in practice this seems not to be true for a substantial number of users on both Macs and Windows (especially, but not limited to, those within some kind of managed corporate IT system).

As far as I can tell, on all hardware/setups where WebGL is disabled in Chrome, it is possible to run it using a different browser (FF, and even IE11). I believe that IE11 only uses software and FF may be less strict with its blacklisting of GPUs, but that doesn't explain why Chrome can't switch to software when hardware is unavailable. Indeed, in some cases, overriding the GPU blacklist in Chrome does seem to work (but presumably is not a good idea).

So firstly, could I check that my assessment of the situation is correct? And secondly, could anyone suggest how to force software rendering (i.e. flags etc.) and/or point me at an issue discussing this?

Any advice would be very much appreciated - even if the process is rather involved it is still worth knowing about as it may be workable for our clients.

update:

@gman points out that there is no software emulation on Macs in Chrome, but that still leaves the question of what's going on in windows.

update 2:

(to partly answer my own question): it seems that (at least on 32bit Chrome on windows) if you go to chrome://components and see SwiftShader is at version 0.0.0, then simply hitting the update button should download the latest veriso,n and hey presto..it works. Not sure about 64bit Chrome though.

update 3:

As @Nicloas says, M59 in Chrome (to be released in May/June 2017) should fix this issue in Chrome on Windows and Linux, with Mac following later.

Answer 1

Quoting my own answer from [email protected]:

I'm happy to let you know that with the upcoming M59 release of Chrome, we have integrated SwiftShader to provide seamless fallback support for WebGL in case the GPU is blacklisted.

We were previously only using SwiftShader as a separately downloaded component, which indeed does not work on managed corporate systems, and required a browser restart. Integrating SwiftShader was only possible after open-sourcing it and substantially reducing its binary size.

You can test it today on Windows using Chrome Canary or the Beta channel, and specifying the --disable-gpu launch flag. Linux is also supposed to work but the libraries were mistakenly not shipped as part of the beta package, which we hope will be rectified in the next update and before it reaches the Stable channel. We haven't started integrating Mac OS X support yet, because Chrome works significantly differently there, but it's on our radar.