How does a browser measure refresh rate?

It times how often the browser can paint a new frame with requestAnimationFrame. Your display caps that rate, and the frame interval converts directly to Hz.

Why is my reading a little below my rated Hz?

Background load, browser throttling, and the OS compositor all add tiny delays. A 144Hz panel often reads around 140 to 144, so a few Hz under the rated number is normal.

Why does it read much lower in another tab?

Browsers throttle requestAnimationFrame in background tabs to save power. Keep this tab active and focused for an accurate measurement.

Why does it show a different monitor's refresh rate?

On a multi-monitor setup, browsers sync frame timing to one display, often your primary one, not always the screen the window is on. Move the browser window fully onto the monitor you want to test. If it still reads wrong, make that monitor your primary display in your OS settings, then run the test again.

Does this show if my high refresh rate is actually enabled?

Yes. If you set 144Hz in your OS but this reads ~60, the display, cable, or graphics setting isn't actually running at the higher rate.

What do the moving beacons show?

They compare frame rates by eye. Each row drives a beacon at 30 fps, 60 fps, and your native refresh rate, so you can feel how much smoother the high rate looks. It's a smoothness comparison, not a pixel response or ghosting measurement.

Is this refresh rate test free?

Yes. There's no signup and no download. The counter runs in your browser off your display's own frame timing, and nothing is stored.

Refresh Rate Test

Measure your monitor's real refresh rate in the browser. See live Hz, frame timing, and stability to confirm a 60, 120, 144, or 240Hz panel runs at full speed.

Detected refresh rate

30 fps

60 fps

Native

Track a beacon with your eyes. The native row should glide; 30 and 60 fps stutter more on a high refresh display.

Min

Max

Frames

Let it run a few seconds for the average to settle. Keep this the active, focused tab - browsers throttle requestAnimationFrame in background tabs, which would read low.

Multi-monitor setup? The browser can report your primary display's rate, not the screen this window sits on. Drag the window fully onto the monitor you want to test. If the number still looks wrong, set that monitor as your primary display.

Measure the refresh rate your screen is really running, and confirm your 144Hz or 240Hz panel didn’t quietly fall back to 60Hz.

How to use

Start measuring. Click Start measuring. The tool counts frames with requestAnimationFrame and shows the detected rate live.
Let it settle. Wait a few seconds. The average smooths out the first noisy frames and settles on your real refresh rate.
Read the result. The big number is your measured Hz. Min and Max show how stable it stayed during the run.

Why test this

Setting a refresh rate in your OS and actually getting it are two different things. A high-refresh monitor will quietly fall back to 60Hz over the wrong cable, on the wrong port, or when a display setting never got switched after a driver update. The drop is easy to feel but hard to confirm by eye. This test measures what the browser can actually paint, which your display caps, so it reports the rate your screen is really running right now. Run it after plugging in a new monitor, swapping a cable, or changing graphics settings to confirm 120, 144, 165, or 240Hz is live and not silently throttled. It's also a fast sanity check when motion looks less smooth than it should. If the number reads far below what you paid for, the problem is in the chain, not your imagination.

What the results mean

The large number is your measured refresh rate in hertz, taken from the average time between frames, and the closest standard line maps it to a common panel rating like 60, 120, or 144Hz. Expect it to land a touch under the rated figure. A 144Hz display usually reads around 140 to 144 once compositor and browser overhead are counted, and that small gap is normal. Min and Max show how steady the rate stayed. Tightly clustered values mean smooth, consistent output. A wide spread points to background load or throttling rather than a hardware fault. If you run adaptive sync (FreeSync or G-Sync), the panel changes its refresh rate on demand, so turn it off for a fixed-rate baseline. The beacon rows let you compare frame rates by eye. Follow one row: the native rate glides while the 30 and 60 fps rows visibly stutter, so a high refresh panel is easy to feel before you even read the number. Keep this tab active and focused while measuring, because browsers throttle the frame timer in background tabs, and that alone can drag the reading down to a misleading 30 or 60Hz.

FAQ

How does a browser measure refresh rate?: It times how often the browser can paint a new frame with requestAnimationFrame. Your display caps that rate, and the frame interval converts directly to Hz.
Why is my reading a little below my rated Hz?: Background load, browser throttling, and the OS compositor all add tiny delays. A 144Hz panel often reads around 140 to 144, so a few Hz under the rated number is normal.
Why does it read much lower in another tab?: Browsers throttle requestAnimationFrame in background tabs to save power. Keep this tab active and focused for an accurate measurement.
Why does it show a different monitor's refresh rate?: On a multi-monitor setup, browsers sync frame timing to one display, often your primary one, not always the screen the window is on. Move the browser window fully onto the monitor you want to test. If it still reads wrong, make that monitor your primary display in your OS settings, then run the test again.
Does this show if my high refresh rate is actually enabled?: Yes. If you set 144Hz in your OS but this reads ~60, the display, cable, or graphics setting isn't actually running at the higher rate.
What do the moving beacons show?: They compare frame rates by eye. Each row drives a beacon at 30 fps, 60 fps, and your native refresh rate, so you can feel how much smoother the high rate looks. It's a smoothness comparison, not a pixel response or ghosting measurement.
Is this refresh rate test free?: Yes. There's no signup and no download. The counter runs in your browser off your display's own frame timing, and nothing is stored.

Every measurement on this site comes from a documented browser API and a stated formula, and we are open about what a browser cannot see. Read how we test.

Was this tool useful?

Related tests

Monitor Test

Test your monitor in the browser with full-screen color, gradient and grid patterns. Spot backlight bleed, IPS glow, banding and dead pixels in minutes.

Embed on your site

Dead Pixel Test

Find dead, stuck, and hot pixels. Cycle full-screen solid colors in your browser, no install, and check every pixel on a monitor, laptop, or phone.

Embed on your site

Reaction Time Test

Test your reaction time online. Click the moment the screen turns green and your speed in milliseconds shows up. Run many rounds and trust the average.

Share your result
Embed on your site

Phone Refresh Rate Test

Check what Hz your phone display is actually running. Browser test, Android Developer overlay, and why adaptive refresh drops the rate when it matters most.

Share your result
Embed on your site

Embed the refresh rate test on your page

Reviewing a monitor or a high-Hz panel? Drop the refresh rate test in so readers read their real screen Hz on the spot. One snippet, full-screen ready, and they can share the refresh rate result.

Want the whole set on your pages? See every tool you can embed →