Browser FPS Meter

Scrolling feels choppy and you cannot tell whether the page, the browser or the laptop is at fault. This page draws three live numbers: the frame rate of the last frame, the average over the past 5 seconds, and the worst single frame in that same window. It is good for comparing scenarios back to back: on battery versus plugged in, with and without that extension enabled, Chrome versus Firefox.

Under the hood it is a requestAnimationFrame loop. On every frame it measures the gap since the previous one and divides 1000 by it, keeping the values in a rolling 5-second window. The minimum is the worst individual frame in that window, so a single 100 ms hitch drops it to 10 and it only recovers once those 5 seconds roll off. The ceiling is your display: a 60 Hz panel gives you 60 and nothing more.

Measurement starts on its own when the page loads, with no start or reset button. It measures this page, which is essentially idle, so treat the number as the ceiling your browser can deliver rather than the frame rate of your own site or game. For that, use the Performance panel in DevTools on the real page. Browsers throttle requestAnimationFrame in background tabs, so keep this tab visible. Nothing is sent anywhere.