What This FPS Test Measures
This tool uses the browser's requestAnimationFrame callback, which fires once per display refresh. By measuring the time between consecutive callbacks we derive the frames-per-second rate the browser is actually achieving on your device. The result is capped by two things: your monitor's refresh rate (since rAF can't fire faster than the display can update) and any throttling your browser applies (background tabs, power saving, GPU pressure).
Current, Average, Min, Max — And 1% Low
Raw FPS numbers fluctuate frame-to-frame, so the meaningful metrics are the averages across a sustained run. "Average" is the smoothed mean of every half-second of rendering. "1% low" is the slowest 1% of frames — this is the number that actually feels like stuttering when gaming or scrolling. A perfect 60 Hz setup shows 60 average / 60 min / 60 max / 60 1%-low. A stuttery setup might show 60 average but 38 for 1%-low, which will feel choppy even though the average is high.
Detecting Your Monitor Refresh Rate
The max FPS over a sustained run is effectively your display refresh rate (as the browser sees it). Common values:
- ~60 Hz: standard office monitor, most budget laptops.
- ~75 Hz: entry-level gaming monitors.
- ~120-144 Hz: mid-range gaming monitors.
- ~165 Hz: common premium gaming.
- ~240 Hz: high-end competitive gaming.
If you expected 144 Hz and see 60 Hz, check Windows Display Settings → Advanced → Refresh rate, and make sure your monitor is plugged into a DisplayPort or HDMI 2.0+ cable with enough bandwidth.
Why Browsers Throttle Background Tabs
Chrome, Firefox, and Edge all throttle background tabs to save battery and CPU. A tab not in the foreground typically drops to 1 Hz (one frame per second) or suspends rendering entirely. For an accurate reading, keep this tab focused and your browser window in the foreground. Also close other heavy tabs — if another tab is doing GPU work it can steal frames from this one.