the os predicts your cursor path before you move · coalesced + predicted pointer events · real-time lookahead · runs locally
what is this
your operating system predicts where your pointer is heading and delivers future positions to the browser before your hand gets there. the white trail is the true past (coalesced high-rate events). the amber dot is now. the red dashes are where the os thinks you are going.
move your pointer here
─ coalesced past● now╌ predicted future
move your pointer or finger into the area above
why this matters
- every os does this. windows, macos, android, and chromeos all run pointer prediction at the compositor or input driver level to reduce perceived latency. browsers expose it via the pointer events api — any page can read the future.
- slow down to see it clearly. move your cursor at a crawl and watch the red dots overshoot ahead — the os committed to positions you had not yet reached. the faster you move, the further ahead it predicts.
- coalescing is the other half. a 1000 hz gaming mouse reports 1000 events per second; the browser coalesces these into ~60fps frames.
getCoalescedEvents()recovers the full-rate sub-frame path between renders — important for ink and drawing apps. - touch and stylus too. active styluses predict ink strokes 30–50ms ahead. this is why digital ink feels immediate even though the screen refreshes at 60hz.