Refresh Rate Test

How to use

1. Pick your rated Hz. Tap the refresh rate printed on your monitor's box or spec sheet. A browser can't read the rating from the display, so the test takes it from you.
2. Start measuring. Click Start measuring and keep this tab in front. The tool times every frame the browser paints with requestAnimationFrame.
3. Read the verdict. After about two seconds the verdict says Full rate, or the rate your screen really runs at. If it runs below the rating, work through the checks under the verdict in order.

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 big number is your steady refresh rate in hertz: one second divided by the average gap between frames, with dropped frames left out so a single hiccup can't pull it down. The verdict under it checks that number against the rating you picked. Full rate means it landed within 2 percent. A verdict such as 120 Hz, not 144, means your screen really runs at 120, and the checklist under the verdict covers the usual causes in order. Above means the screen runs faster than the rating you picked, so check the box again. The frame time chart draws one bar per frame for the last 120 frames. Even bars mean steady pacing. An amber bar is a dropped frame, a gap longer than one and a half frame times. Frames and Dropped count from the moment the run settles, and Spread is how much the on-time gaps vary, in milliseconds. All of this is the browser's frame clock, not the panel's own scanout. Keep this tab active and focused while you measure. Browsers throttle the frame timer in background tabs, and that alone can drag the reading down to 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 144Hz monitor running at 60Hz?

Usually a setting, a cable or a port holds it there. Start with the OS. On Windows, open Settings, System, Display, Advanced display and pick the top rate under Choose a refresh rate. If the rate is missing from that list, the cable or port cannot carry it. Safari reads about 60 even when all of that is right. It draws pages near 60 fps by default, so a 120Hz Mac shows about 60 until you turn off its Prefer Page Rendering Updates near 60fps feature flag. Every fix in order, with the cable bandwidth table

How much bandwidth does a high refresh rate need?

More than older links carry, and the need grows with resolution times Hz. DisplayPort 1.2 tops out at 21.6 Gbps and DisplayPort 1.3 and 1.4 at 32.4 Gbps. HDMI 2.1 goes up to 48 Gbps with an Ultra High Speed HDMI cable, enough for 4K at 120Hz. An older HDMI port or cable is the usual reason a 1440p or 4K monitor gets stuck below its rated Hz.

Why does it read 143.9 instead of 144?

Some display modes sit a hair under the round number, like 59.94Hz for a 60Hz mode, and the frame clock adds a little noise. The verdict counts anything within 2 percent of your rating as Full rate, so those small gaps pass. A bigger gap means one of the checks under the verdict is holding the rate down.

What counts as a dropped frame?

A frame that shows up more than one and a half frame times after the one before it. The chart marks it in amber. It means the browser missed a refresh, usually from background load. Some overclocked panels skip refreshes inside the monitor, and the browser never sees that. A clean chart does not clear an overclock.

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.

What do the moving beacons show?

Watch them side by side to see what each frame rate looks like. Each row moves a beacon at 30, 60, or 120 fps, and the last row runs at your native rate. Rows at or above your screen's rate drop out, so every row left is slower than native. Go full screen for a bigger view. The rows show smoothness only. They don't measure pixel response or ghosting.

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.

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, and it's full-screen ready.

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