Safari uses Quartz/Core Graphics for the painting, via OpenGL if applicable. Chrome uses Skia/Ganesh, sometimes via OpenGL--Chrome is more conservative about wh

Safari uses Quartz/Core Graphics for the painting, via OpenGL if applicable. Chrome uses Skia/Ganesh, sometimes via OpenGL--Chrome is more conservative about when it enables the OpenGL-based painting than Safari is, I believe. If everything else on your machine is slowing down, then chances are good that Safari is hitting some bad case in the way it uses your GPU. CG::OGL may not be optimized well for this use case. (In general retrofitting CPU-based 2D graphics APIs to run on GPUs, as both Chrome and Safari attempt to do, is difficult.) Or the layerization heuristics may be going awry in Safari--unlike Chrome, which does things manually, Safari has a completely different implementation of layers that exports the layer structure of the page to the OS window server.