[rMBP]

Does not work in Safari on Mavericks using a rMBP @1680x1050 retina resolution. It suggests browser zooming be set to 100% which it is.

[modeless]

Thanks for the report; I see the problem. I'll look into fixing it, but in the meantime you can get it running by enabling WebGL in Safari (under the Develop menu, and if you don't have a Develop menu you can enable it in Preferences->Advanced).

Spoiler: Safari actually gets a very good score (relative to other browsers).

[aaron42net]

I also get "Failed to find test pattern on screen." in Safari with WebGL enabled on a Mid 2011 Mac Mini running 10.9 with dual monitors. View is set to "Actual Size", and I've tried moving the Safari window between monitors.

Other scores - Chrome 30: 2.4/10. Firefox 24 and 25: 1.2/10.

[rMBP]

Enabling WebGL works. My three tests scored 8.7, 6.7 and 6.3 respectively. I guess Safari, like me, hates repetitive tasks. :)

[modeless]

:) There is a lot of run-to-run variance. Some of it is real in that browsers do give different results, and some of it is just test noise. I'm still working on improving the robustness. Recently I've been working on hardware latency measurement which gives more reliable numbers.

[selectodude]

I do have WebGL enabled, and it can't pick up the test pattern.