Quick answer
60 Hz means about 16.7 ms per frame, 144 Hz about 6.9 ms and 240 Hz about 4.2 ms. Open this page on the screen you want to check and wait a few seconds.
How to use the Refresh Rate Test
- Open this page on the screen you want to test. If you have several monitors, move the browser window onto that screen.
- Wait a few seconds while the test measures. Keep the tab in the foreground.
- Read the measured refresh rate and the closest standard value (for example 144 Hz).
- If it's lower than your monitor supports, change the refresh rate in your display settings, then click Restart measurement.
Example
You bought a 144 Hz gaming monitor, but the test shows 60 Hz. On Windows, you open Settings › System › Display › Advanced display and change the refresh rate to 144 Hz. You also check that you're using a DisplayPort or suitable HDMI cable, since older HDMI cables often limit you to 60 Hz. The test now shows 144 Hz and the ball moves noticeably more smoothly.
How it works
Browsers draw animations in sync with your display using requestAnimationFrame. Each time the screen refreshes, the browser calls the page once. The tester records the time between these calls and takes the median of the last 120 frames: a 60 Hz screen gives about 16.7 ms per frame, 144 Hz about 6.9 ms and 240 Hz about 4.2 ms.
The graph shows each frame time. A flat line means smooth output; spikes mean dropped or late frames, which you feel as stutter.
The result reflects what your browser actually renders. Battery saving modes, a background tab or some browser settings can limit the rate, so plug in laptops and keep the tab visible.
Why your screen may not reach its full Hz
- Windows: Settings › System › Display › Advanced display › Choose a refresh rate. New monitors often start at 60 Hz.
- macOS: System Settings › Displays › Refresh rate. MacBook Pro screens use ProMotion and adapt between 24 and 120 Hz.
- Cable limits: older HDMI 1.4 ports and cables often hold high-refresh monitors to 60 Hz, and 4K to 30 Hz. Use DisplayPort or a certified HDMI 2.0/2.1 cable for higher rates.
- Laptops on battery: many laptops drop to 60 Hz on battery to save power. Plug in and test again.
- Two monitors with different rates: move the browser window fully onto the screen you're testing, then restart the measurement.
Frequently asked questions
Why does it show 60 Hz on my 144 Hz monitor?
The refresh rate is probably still set to 60 Hz in your display settings, or your cable or port doesn't support higher rates. Use DisplayPort or an HDMI 2.0+ cable and select the highest rate in your system's display settings.
Why is the number not exactly 144?
Small timing variations are normal. Monitors also often run at values like 143.9 or 59.94 Hz. The closest standard rate shows what your monitor is set to.
What's the difference between refresh rate and FPS?
The refresh rate is how often your monitor updates the image. FPS is how many frames your game or app produces. To see all frames, your FPS and refresh rate should be matched or synced.
Does this work on phones?
Yes. Many modern phones have 90 or 120 Hz screens. Note that power saving modes often limit them to 60 Hz.
Why does the measurement jump around?
Background activity, other tabs or power saving can delay frames. Close heavy apps, plug in your laptop and restart the measurement.