Refresh rate is how many times per second a monitor redraws the image, measured in hertz (Hz). This test times the browser's frame callbacks (requestAnimationFrame) for 3 seconds and divides 1000 by the median interval in milliseconds. If the result is within 3% of a standard rate such as 60, 120, 144, 165 or 240 Hz, it shows that standard rate.
| Frame interval | 1000 ÷ interval | Refresh rate shown |
|---|---|---|
| 16.67 ms | 59.99 Hz | 60 Hz |
| 13.33 ms | 75.02 Hz | 75 Hz |
| 8.33 ms | 120.05 Hz | 120 Hz |
| 6.94 ms | 144.09 Hz | 144 Hz |
| 6.06 ms | 165.02 Hz | 165 Hz |
| 4.17 ms | 239.81 Hz | 240 Hz |
| 7.50 ms | 133.33 Hz | 133 Hz (no standard rate within 3%, so it is rounded) |
How to read your refresh rate test result
The big number is the rate the monitor showing this window is actually running at. A 144 Hz monitor set to 144 Hz reads about 144.1 Hz measured, a frame interval near 6.94 ms, and 144 Hz, because 1000 ÷ 6.94 ≈ 144. At 60 Hz the interval is about 16.67 ms, and 1000 ÷ 16.67 ≈ 60.
The test starts a moment after the page opens and finishes after 3 seconds. The first 10 frames are skipped because they are often irregular. Using the median instead of the average keeps a few slow frames from pulling the number down. While it runs, a block moves 1 pixel per frame.
Dropped frames counts intervals longer than 1.5 × the median. If there are many, close background apps and test again with this tab in front. If you switch tabs, the browser stops drawing, so the test pauses and resumes when you come back.
How to set 144Hz on Windows 11 and Mac
On Windows 11, go to Settings > System > Display > Advanced display and pick the rate next to Choose a refresh rate. With several monitors, select the one you want at the top of that page first. If 144 Hz is missing from the list, that monitor, cable and port combination may not support it at the current resolution.
The same page may have a Dynamic refresh rate switch, which lets Windows change the rate based on what you are doing. Microsoft says it needs a display with variable refresh rate and at least 120 Hz. If your readings jump around, turn it off and test again.
On a Mac, choose Apple menu > System Settings > Displays and open the Refresh Rate pop-up menu. On 14-inch and 16-inch MacBook Pro models with Apple silicon, ProMotion gives an adaptive rate up to 120 Hz; you can also choose a fixed rate. For an external display, select it in Displays first.
144Hz monitor only showing 60Hz
Check the setting first; if it is right, suspect the cable and port. When the result is 61 Hz or lower, the test lists these checks under the result.
HDMI version matters. HDMI.org lists HDMI 1.4b support for 1920 × 1080 at 120 Hz and 3840 × 2160 at up to 30 Hz. HDMI 2.0 raised bandwidth to 18 Gbps for 4K at 50/60 Hz. High refresh monitors often reach their top rate only over DisplayPort or a newer HDMI port, so check the manual for the maximum rate per port and connect with that port and a matching cable.
Laptop battery saver can hold the rate at 60 Hz, and so can turning off hardware acceleration in the browser. With multiple monitors, the result is for the monitor this window is on, so move the window and test again.
Does G-Sync or FreeSync lower the reading?
It can. A variable refresh rate monitor redraws when the graphics card sends a frame, so a browser that draws slowly can read below the monitor's maximum.
This test measures how fast the browser draws. It does not read the monitor's maximum or the value set in Windows. Use the display settings above for the configured rate and this test to confirm the browser actually gets it. An odd value such as 133 Hz, with no standard rate within 3%, usually points to variable refresh or dropped frames.
FAQ
It says 143.9 Hz. Is that normal?
Yes. Browser timestamps have small errors, so the decimals wobble. Within 3% of 144 the big number still shows 144 Hz.
Why do I get a different number each time?
Moving the mouse a lot or opening other windows drops frames. Keep this tab in front, hands off, and test again. Variable refresh and Windows Dynamic refresh rate can also change the reading.
Is a refresh rate test the same as a ghosting test?
No. Refresh rate is how often the screen redraws. Ghosting is a trail behind moving objects caused by slow pixel response time, and this test does not measure it.
Do I need to install anything or grant permissions?
No. The test only times how often the browser draws and runs entirely on the page.
Sources: WHATWG HTML Standard: animation frames (requestAnimationFrame) · Microsoft Support: Change your display refresh rate in Windows · Apple Support: Change the refresh rate on your Mac · HDMI Licensing Administrator: HDMI 1.4b specification · HDMI Forum: HDMI 2.0 announcement (2013) · Updated 2026-10-14