A WebGL primer
Conversion of existing 3D animation to WebGL
One reason is that a Unity to WebGL conversion does not produce clean optimized code. Another reason we do not recommend this route is that Unity WebGL content is not currently supported on mobile devices. It may still work, especially on high-end devices, but many current devices are not powerful enough and don’t have enough memory to support Unity WebGL content in a satisfactory manner. Also consider that when the hi-res versions were created the size of the scenes might not have mattered that much for an application running on a top-specked gaming machine but online through a browser it would take ages to load.
Versions: There are WebGL 1.0 and 2.0. We recommend version 1.0 since 2.0 has limited support on mobile devices.