I've read the standard [0], to be fair there is nothing in there explicitly indicating that some contexts might be unsupported, except the vague "if this does n

I've read the standard [0], to be fair there is nothing in there explicitly indicating that some contexts might be unsupported, except the vague "if this does not throw an exception" condition, which is easy to miss. [0] https://html.spec.whatwg.org/multipage/canvas.html#the-offscreencanvas-interface https://html.spec.whatwg.org/multipage/canvas.html#the-offsc...