How does this test measure refresh rate?
The page calls requestAnimationFrame, which the browser fires once per display refresh. We record the timestamp gap between consecutive callbacks for 5 seconds, then take the median interval and invert it to get Hz. The median (not the mean) rejects occasional missed frames from background tabs or GC pauses. The result is then snapped to the nearest standard locked rate — 60, 75, 90, 120, 144, 165, 240, 360, 480 Hz — so a noisy 143.7 reads cleanly as 144 Hz. Accuracy is typically within 0.5 Hz on a quiet system.
Why does my 144 Hz monitor report only 60 Hz?
Browsers cap requestAnimationFrame at 60 Hz under several conditions: laptop on battery saver, Chrome with hardware acceleration disabled, Firefox with a non-composited window, or any browser whose tab is unfocused. Windows itself may also be running the display at 60 Hz despite the panel's capability — check Display Settings → Advanced display → Refresh rate. For laptops with hybrid graphics, ensure the browser is running on the dGPU. Try fullscreen (F11), close other tabs, and re-run.
What's a good refresh rate for gaming vs office work?
60 Hz is fine for documents, web, and video (most content is 24–60 fps). 120/144 Hz noticeably reduces motion blur in scrolling and cursor tracking — the perceptual jump from 60 is the largest single upgrade. 240 Hz benefits competitive FPS (CS, Valorant, Overwatch) where 1–2 ms input-to-photon latency matters. 360–480 Hz is diminishing returns territory: useful only with sub-1ms response times on OLED or fast TN, and only at the very top of esports play.
Refresh rate vs response time — what's the difference?
Refresh rate (Hz) is how many times per second the panel can display a new frame. Response time (ms) is how fast a single pixel can change colour. A 240 Hz monitor refreshes every 4.16 ms, so any pixel slower than that will smear into the next frame — that's ghosting. A 144 Hz panel with 1 ms GtG response is sharper in motion than a 240 Hz panel with 5 ms response. Test response with /monitor/ghosting (pursuit-camera method); the UFO test on this page shows their combined effect.
What does the UFO test reveal that the Hz counter doesn't?
The Hz counter only proves the browser is animating at full rate. The UFO test reveals actual motion clarity — how cleanly your panel can render a moving object. Track the UFO with your eyes (smooth pursuit). On a fast OLED at 240 Hz, the craft stays crisp. On a slow IPS, it leaves a blur trail. On overdriven VAs, you'll see inverse ghosting (a pale halo in front of the craft). Increase speed to 1600 or 3200 px/s to stress the panel.
Does VRR / G-Sync / FreeSync affect this test?
Yes — variable refresh rate locks the display to whatever rate the source is delivering, up to the panel's max. Since requestAnimationFrame on an idle browser tab usually drives the display at its maximum advertised rate, VRR doesn't change the reading. But if the browser is busy and rAF drops to 90 Hz, VRR will let the panel drop with it, and the test will report 90 Hz instead of 144. To check your peak panel rate, ensure the system is otherwise idle. See also /monitor/ghosting and /monitor/banding.