Hz test: how many frames per second does your screen show?
Measuring starts right away: the browser counts how often per second it may draw a new frame. Below, objects move at different frame rates – so you can see how smoothly your screen shows motion.
How it is calculated
How the Hz test works
The refresh rate says how often a screen shows a new image per second – 60 Hz on many screens, 120, 144 Hz or more on gaming monitors and some phones. The test starts by itself; after a few seconds the value is stable.
- Open the page and wait briefly until the number settles.
- Below the result, the motion test shows several objects: the higher a row’s frame rate, the smoother it should move – up to the limit of your screen.
- “Speed” changes the pace, “Measure again” starts over.
How it is measured
Browsers generally call requestAnimationFrame in step with the display’s refresh rate (MDN, HTML Standard). The tool measures the gaps between these calls with performance.now(), takes the median – which is insensitive to single outliers – and converts 1000 ÷ median into Hz. A dropped frame here is a gap longer than 1.5 times the median (a definition of this tool).
Limits
- It measures how often the browser draws – not the panel directly. Power saving, background tabs or a browser limit can give a lower value.
- With variable refresh rates (e.g. adaptive sync or phones that slow down when idle) the value can fluctuate.
- With several monitors the value applies to the screen the window is on.
Frequently asked questions
How do I find out how many Hz my monitor has?
Open the page and wait a few seconds. The test shows the rate at which the browser draws – usually the refresh rate set in your system.
Why does it show 60 Hz although my monitor supports 144 Hz?
Often the operating system is still set to 60 Hz, the cable limits it or a power-saving mode is on. Check the display settings and measure again.
How accurate is the measurement?
It uses the median of many frame gaps and is therefore robust. But it measures the browser’s drawing rate, not the hardware directly.
What are dropped frames?
Frame gaps longer than 1.5 times the median – so skipped frames. A few are normal; many point to load or throttling.
Does the test work on a phone?
Yes. Some phones lower the rate when idle or in power-saving mode; swipe briefly across the screen and measure again.
Sources and legal basis
- MDN Web Docs – Window.requestAnimationFrame()
- WHATWG HTML Standard – Animation frames
- MDN Web Docs – Performance.now()
As of:
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