How to use the Refresh Rate Test
- Close GPU-heavy apps and place this page on the display you want to test (drag it there on multi-monitor setups).
- Keep the tab in the foreground and wait 3–5 seconds for a stable reading and the nearest standard rate.
- Check whether the frame-time graph is flat; spikes mean dropped frames or stutter.
- Run the moving-block test to compare blur and ghosting at different speeds.
How a browser measures refresh rate
Browsers call requestAnimationFrame before each screen refresh. The tool records the time between calls (frame time) and converts the stable median to Hz: 16.7 ms is about 60 Hz, 8.3 ms about 120 Hz and 6.9 ms about 144 Hz. The result is snapped to the nearest common rate for easy comparison with the spec sheet.
Why the result differs from the rated Hz
Common causes: the high refresh rate is not selected in display settings, the cable or port lacks bandwidth (HDMI 1.4 cannot carry 4K 144 Hz), laptop power saving or phone low-power mode caps the rate, hardware acceleration is off, or the page sits on a different monitor. With VRR the reading can float with load.
Frame time, jitter and dropped frames
Stable frame times look smooth. High jitter (frame-time standard deviation) points to unstable scheduling, and any frame longer than 1.5 times the average counts as a drop. If games or videos stutter, start your troubleshooting here.
Frequently asked questions
Is a browser refresh rate test reliable?
It is reliable enough to confirm whether high refresh is active. It measures the real browser frame cadence, which can be limited by the browser, background-tab throttling or power saving, so it is not a hardware instrument.
Why does Safari show only 60 Hz?
Some Safari versions and Low Power Mode cap web animation at 60 Hz. Turn off Low Power Mode on iPhone or iPad, or test in Chrome or Edge.
How do I set my monitor to 144 Hz?
Windows: Settings → Display → Advanced display → Choose a refresh rate. macOS: System Settings → Displays → Refresh rate. Use DisplayPort or a high-refresh HDMI cable and choose the mode in your GPU control panel.
What does the moving block test show?
It moves a block at a fixed speed so you can compare ghosting and motion blur by eye. Higher refresh rates and faster pixel response produce sharper edges.
Does the test use many resources?
No. It only records frame times and draws a simple graph, and measurement pauses when the tab is in the background.