Hardware acceleration flags in Firefox

1. Open about:config tab
2. Search for azure
   gfx.canvas.azure.backends direct2d,skia,cairo
   gfx.content.azure.backends direct2d
   gfx.content.azure.enabled true
3. Search for direct2d (Windows)
   gfx.direct2d.disabled false
4. Search for directwrite
   gfx.font_rendering.directwrite.enabled true
5. Search for layers
   layers.acceleration.disabled false
   layers.acceleration.draw-fps false
   layers.acceleration.force-enabled false
   layers.async-video.enabled false
   layers.composer2d.enabled false
   layers.offmainthreadcomposition.animate-opacity false
   layers.offmainthreadcomposition.animate-transform false
   layers.offmainthreadcomposition.log-animations false
   layers.prefer-d3d9 false
   layers.prefer-opengl false
6. Also check for gfx.content

Acceleration test
CSS 3D demo