Works in Chrome; in Safari and Firefox, YouTube shows the original, distorted video without even a message to the effect that it's not the intended experience.

Works in Chrome; in Safari and Firefox, YouTube shows the original, distorted video without even a message to the effect that it's not the intended experience. Both of these browsers support WebGL, of course, so I doubt there is any technical reason only Chrome is supported. Why am I not surprised that this is nevertheless the case?