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Monitor · refresh rate test

Refresh Rate Test: What Hz Is Your Screen Running At?

This refresh rate test measures how many frames per second your screen is actually drawing in the browser — 60, 120, 144, 240 Hz or more — by timing every frame for about three seconds. Pick your monitor's advertised rate and it tells you whether you're getting it. A 144 Hz monitor that measures 60 Hz is almost always a setting, cable or port problem, not a broken monitor; the result links to the fix. Runs in your browser, nothing is uploaded.

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How the refresh rate test works

  1. Step 1

    Pick the advertised rate

    Optional: choose the refresh rate on your monitor's box or spec sheet, so the result can compare.

  2. Step 2

    Measure

    Keep the tab in front for about four seconds. The browser reports the time of every frame it draws; we take the median frame time.

  3. Step 3

    Read the verdict

    You get the refresh rate, frame time and missed frames — and whether it matches what you paid for.

How we judge the result

ResultRuleWhat it usually means
MatchesWithin 3% of the advertised rateYou're getting the refresh rate you paid for.
Lower than advertisedMore than 3% belowA setting, cable, port or driver limit — rarely a faulty monitor.
Higher than advertisedMore than 3% aboveThe advertised value picked doesn't match this screen; check the spec sheet.
UnstableMore than 10% of frames missedThe computer was busy or throttled; close heavy apps and measure again.

Frame intervals longer than 100 ms (a hidden tab or a pause) are ignored; the estimate snaps to the nearest common rate when within 4% of it.

What this test can and can't tell you

  • Reliable: Measures the rate your browser really draws at. Browsers run their animation callback once per display refresh, so frame timing reveals the active refresh rate.

  • Estimate: Browsers can cap it. Battery-saver modes, background tabs, and Safari's default 60 fps limit on some Macs can make the browser draw slower than the screen can. Try Chrome or Edge on mains power if the number looks low.

  • Limit: Not response time or input lag. Refresh rate is how often the picture updates. It doesn't measure pixel response time, overdrive ghosting or input lag.

Refresh Rate Test — frequently asked questions

How do I check my monitor's refresh rate?
Run this test for the rate your browser is actually drawing at. To see or change the setting: on Windows 11 go to Settings › System › Display › Advanced display and choose a refresh rate; on a Mac, open System Settings › Displays and use the Refresh Rate menu (on supported displays). The guide linked below covers both with troubleshooting.
Why is my 144 Hz monitor stuck at 60 Hz?
The usual causes are: the refresh rate was never changed from 60 Hz in display settings; the cable or port can't carry the full rate (use DisplayPort, or the HDMI port and version the monitor specifies); the wrong input is selected; or the graphics driver is outdated. Laptops on battery and some browsers can also cap animation at 60 Hz.
Is this test accurate?
It measures the rate the browser renders at, which equals your active refresh rate when nothing is throttling it. We take the median of a few hundred frame intervals, snap to the nearest standard rate, and flag the run as unstable if more than 10% of frames are missed.
Does G-Sync or FreeSync change the result?
Variable refresh lets the monitor follow the game's frame rate, but a browser animating continuously normally runs at the monitor's maximum rate, so the test still shows the configured maximum.
Can I test refresh rate on a phone?
Yes. Many phones run at 90 or 120 Hz but drop to 60 Hz in power-saving mode or in some browsers. On iPhone with ProMotion, Safari may report 60 Hz unless its 120 Hz option is enabled.

Sources

  1. Window: requestAnimationFrame() method — MDN Web Docs
  2. Change the refresh rate on your monitor in Windows — Microsoft Support
  3. Change the refresh rate on your MacBook Pro or Apple display — Apple Support

Last reviewed .

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