Refresh Rate Test

Open the page and wait a second: the big number is the refresh rate your display is running at right now, in hertz. It is measured, not looked up — the tool times every frame your browser draws and works out how often the screen refreshes, so it shows what you actually get rather than what the box promised.

Below the headline you get the exact measured rate (59.94 Hz and 60 Hz are different things), the frame time in milliseconds, frame-time jitter, dropped frames, and a live graph of the last few seconds of frames. Red bars in the graph are frames that arrived late.

How it measures

Browsers paint at most once per display refresh and fire requestAnimationFrame in step with it. The tool records the interval between consecutive frames, takes the median as a robust first guess, averages the intervals that agree with it, and treats anything near a whole multiple of the frame period as dropped frames rather than letting it drag the average down. Gaps longer than a quarter of a second — a hidden tab, a debugger pause — are ignored.

The motion test

Three flying saucers cross the screen at different speeds, each moving a fixed number of pixels every frame. Track one with your eyes: at 144 Hz it looks noticeably sharper and smoother than at 60 Hz. A hitch or stutter is a dropped frame; a smeared trail is motion blur from the panel's pixel response and sample-and-hold persistence, which overdrive and backlight-strobing (ULMB, ELMB, DyAc) modes reduce.

Common uses

• Check that a new 120, 144, 165 or 240 Hz monitor is actually running at its rated speed
• Catch the classic mistake of a high-refresh monitor stuck at 60 Hz because of the cable, port or OS setting
• Confirm a laptop's 120 Hz screen isn't being held at 60 Hz by battery saver
• Compare motion clarity between overdrive and blur-reduction settings
• Spot stutter and dropped frames caused by background load

Example

144 Hz gaming monitor over HDMI 1.4

60 Hz · 16.67 ms frame time

HDMI 1.4 can't carry 1440p at 144 Hz, so the monitor fell back to 60 Hz. Switching to DisplayPort and choosing 144 Hz in the display settings fixes it.

Limitations

• The reading is of the monitor the browser window is on. Drag the window to another screen and press Restart measurement.
• Variable refresh rate (G-Sync, FreeSync, Apple ProMotion) lets the display slow down when little is moving, so you may see a lower or fluctuating number; that's VRR doing its job.
• Battery saver, Low Power Mode, some power plans, and Firefox's fingerprinting protection can cap the browser at 60 Hz or less even on a faster screen.
• Background tabs don't draw at all, so measuring pauses until the tab is visible again.
• A browser can't see refresh rates above what it renders; extremely high rates (360 Hz and up) depend on the browser and GPU keeping pace.

How do I know what Hz my monitor is?

Open this page with the browser window on that monitor and wait a second or two — the large number is the measured refresh rate. To see what the monitor supports rather than what it is running at, check the display settings: on Windows, Settings → System → Display → Advanced display; on macOS, System Settings → Displays.

Why does my 144 Hz monitor show 60 Hz?

Usually because the OS is set to 60 Hz, the cable or port can't carry the higher rate (older HDMI often can't), or the browser is on a different, 60 Hz screen. Select the highest refresh rate in your display settings, use DisplayPort or a certified high-speed HDMI cable, and turn off battery saver on laptops.

Is the refresh rate test accurate?

Yes, to a fraction of a hertz on a steady display. The browser paints once per refresh, so averaging hundreds of frame intervals pins down the rate closely — it will distinguish 59.94 Hz from 60 Hz. Readings wobble if the computer is busy, if variable refresh rate is active, or if the browser is throttled.

What are dropped frames and jitter?

A dropped frame is a refresh the browser missed, so one frame stays on screen twice as long; it shows up as a stutter in the motion test and a red bar in the graph. Jitter is how much frame intervals vary — under about half a millisecond means smooth, even pacing.

Can a website detect a 240 Hz or 360 Hz monitor?

Yes, as long as the browser and graphics card keep up: Chrome, Edge and Firefox render at the display's full rate. Safari has historically held web pages to 60 frames per second even on 120 Hz ProMotion screens unless that limit is switched off in its feature flags, and most browsers cap the rate in power-saving modes.

What is the UFO motion test?

It's a moving-object test popularised by Blur Busters: objects crossing the screen at known speeds show how sharp motion looks at your refresh rate. Higher refresh rates and blur-reduction modes make the saucers look crisper; stutter means dropped frames, and ghost trails come from slow pixel response.

Why does the reading change when I move the mouse or switch tabs?

With variable refresh rate, the display may run slower when nothing is moving and faster when something is. When a tab is in the background the browser stops drawing it entirely, so the tool restarts its measurement when you come back.