The “game” part at the top measures human lag time as a proxy for compositor lag, which is a crude approximation as it also includes monitor input lag as well.

The “game” part at the top measures human lag time as a proxy for compositor lag, which is a crude approximation as it also includes monitor input lag as well. Other tests, including on the same site, are able to get the real-time hardware cursor position which the test code knows is ahead of the last-drawn cursor position and whatever position it’s drawing right now.