Refresh Rate Test

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monitor hz test

Monitor Hz test

Plenty of people buy a 144 Hz monitor and later find the system stayed at 60 Hz. This page measures how many frames the browser really draws per second, and the UFO mode lets you see the smoothness difference with your own eyes.

How Hz is measured in the browser

The browser calls a function for every frame it is about to draw (requestAnimationFrame), usually at the same cadence as the screen. Recording the time of each call for 3 seconds, the typical interval between frames gives the rate: 1000 divided by the median in milliseconds. The median ignores the few dropped frames, and the result is rounded to the nearest common rate such as 60, 120, 144 or 240 Hz.
If the result is lower than expected, check the rate in the system display settings, the cable (an old HDMI version or a poor cable limits the rate), the port in use and the power saving mode. Keep the tab in the foreground: browsers pause animations in hidden tabs.

Common results

144 Hz monitor running at 60

Input: Medir
Expected output: 60 Hz

Almost always a setting: open the system display settings and choose 144 Hz.

120 Hz panel

Input: Medir
Expected output: 120 Hz, valor bruto próximo de 120

The raw value may sit slightly below or above the rounded rate because of small timing variations.

Full tool FAQ

Why does the test show 60 Hz if my monitor is 144 Hz?

The system may be set to 60 Hz, the cable or port may not support more, or the browser may be limited (power saving mode, windowed tab, another monitor). Adjust the rate in the system display settings and measure again.

How does the test compute Hz?

What are dropped frames?

What is the UFO test?

What does the trail mean?

Can I trust the value on phones and laptops?

Why can the measurement come out interrupted?

How do variable refresh rate screens (VRR, G-Sync, FreeSync) show up?

Frequently asked questions

Does the UFO mode measure anything?

It shows smoothness but does not measure: you compare motion sharpness across speeds and across screens. For the Hz number, use Measure mode.

Why does the value vary between measurements?

CPU load, other tabs and power saving modes change the time between frames. That is why the result uses the median and shows the raw value. Repeat with the device charging and no heavy apps open.

Next steps

How Hz is measured in the browser

The browser calls a function for every frame it is about to draw (requestAnimationFrame), usually at the same cadence as the screen. Recording the time of each call for 3 seconds, the typical interval between frames gives the rate: 1000 divided by the median in milliseconds. The median ignores the few dropped frames, and the result is rounded to the nearest common rate such as 60, 120, 144 or 240 Hz.

If the result is lower than expected, check the rate in the system display settings, the cable (an old HDMI version or a poor cable limits the rate), the port in use and the power saving mode. Keep the tab in the foreground: browsers pause animations in hidden tabs.

Common results

144 Hz monitor running at 60

Input: Medir
Expected output: 60 Hz

Almost always a setting: open the system display settings and choose 144 Hz.

120 Hz panel

Input: Medir
Expected output: 120 Hz, valor bruto próximo de 120

The raw value may sit slightly below or above the rounded rate because of small timing variations.

Full tool FAQ

Why does the test show 60 Hz if my monitor is 144 Hz?

How does the test compute Hz?

What are dropped frames?

What is the UFO test?

What does the trail mean?

Can I trust the value on phones and laptops?

Why can the measurement come out interrupted?

How do variable refresh rate screens (VRR, G-Sync, FreeSync) show up?

Frequently asked questions

Does the UFO mode measure anything?

It shows smoothness but does not measure: you compare motion sharpness across speeds and across screens. For the Hz number, use Measure mode.

Why does the value vary between measurements?

CPU load, other tabs and power saving modes change the time between frames. That is why the result uses the median and shows the raw value. Repeat with the device charging and no heavy apps open.