Closing as won't fix. The CPU usage is not a very scientific value - just a rough estimate, as best as can be measured from javascript which typically cannot access the real operating system measurement. In WebGL mode the engine is likely doing the same or less work, but rendering calls are included in the CPU time; in canvas2d mode the browser makes the rendering calls, so are probably not included in the CPU time. Other benchmarks show that WebGL mode is almost always faster than canvas2d mode, so I think this explanation suffices.