Check your monitor's real refresh rate in Hz automatically as soon as the page opens. Inspect live frame-time stability, compare native vs 60 vs 30 fps motion, and run a fullscreen frame-skipping test.
Measuring…
Live measured Hz
—
Matched tier & frame time
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Frame-time jitter (std dev)
0
Dropped / spiked frames
Your Refresh Rate Test Result
Measured
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What this refresh rate test checks
Buying a 144 Hz, 165 Hz or 240 Hz monitor does not guarantee your operating system is actually running it at that speed. Windows, macOS and Linux frequently default new displays to 60 Hz out of the box, and older HDMI cables or USB-C hubs silently cap high-resolution monitors at 60 Hz or even 30 Hz. This tool times `requestAnimationFrame` callbacks across 180 rolling frames to measure the exact refresh rate your browser receives, plots frame-to-frame pacing jitter, and includes a camera-based frame-skipping grid to verify that overclocked monitors aren't dropping frames internally.
Before you start
Keep this browser window on the monitor you want to test. If you use a dual-monitor setup with mixed refresh rates (for example, a 165 Hz primary display and a 60 Hz side monitor), move the browser completely onto the target display.
Plug in laptop power or turn off Battery Saver / Low Power Mode. Windows Energy Saver, macOS Low Power Mode, iOS Low Power Mode and Android battery savers automatically throttle ProMotion and high-Hz panels down to 60 Hz.
Enable browser hardware acceleration so frame timing isn't limited by software compositing.
How to run the test
Live Hz measurement: Wait 2–3 seconds after opening the page. The live counter stabilizes on your current refresh rate and matches it to the nearest standard tier (60, 75, 120, 144, 165, 240 or 360 Hz).
Check against your monitor's spec: Select your monitor's rated Hz in the dropdown and click Generate Hz report. If your system is stuck below its rated speed, the report gives you the exact OS and cable checklist.
Run the Frame-Skipping Grid (especially on overclocked monitors): Click Launch Fullscreen Frame-Skipping Grid, set your phone camera to a slow shutter speed (~1/10 s to 1/15 s) or Live Photo long exposure, and photograph the screen.
How to read your results (including frame skipping)
Healthy panel (no skipped frames)A 1/10 s camera exposure captures 5–15 adjacent white squares in an unbroken chain.Frame skipping detectedMissing squares inside the bright streak mean the monitor scaler is dropping frames—lower your custom Hz overclock.
Refresh Rate Tier
Frame Interval
Minimum Cable Bandwidth (at 1440p / 4K)
Typical Use
60 Hz
16.67 ms
Any HDMI 1.4 / 2.0 or DisplayPort 1.2
Office, video, standard laptops
120–144 Hz
8.33–6.94 ms
1440p: HDMI 2.0 or DP 1.2 · 4K: HDMI 2.1 or DP 1.4 (DSC)
Safari on macOS / iOS 120 Hz ProMotion: By default, WebKit caps `requestAnimationFrame` at 60 fps on many pages to save battery even when the display runs at 120 Hz. In Safari on macOS, disabling "Prefer Page Rendering Updates near 60fps" in Develop → Experimental Features lets WebKit report the full 120 Hz.
Background downloads or video decoding: Another window playing 60 fps video on an older Windows build or an unaccelerated browser profile can cause periodic frame-time spikes.
HDMI port limitations on monitors: Many 144 Hz and 165 Hz 1440p monitors only support their full refresh rate over DisplayPort, while their HDMI 1.4/2.0 input is locked to 60 Hz or 120 Hz in the monitor firmware.
Refresh rate test vs related tests
A high refresh rate means a new frame arrives every few milliseconds, but the picture will still blur if the liquid crystals cannot switch colors that fast. After confirming your Hz here, open the monitor response time and ghosting test to check motion clarity and tune your overdrive setting, and use the input lag test to verify Game Mode latency.
Frequently asked questions
Why does my 144 Hz or 165 Hz monitor only show 60 Hz?
Almost always because the operating system is still set to 60 Hz. On Windows 11, open Settings → System → Display → Advanced display and choose your highest refresh rate under "Choose a refresh rate". On macOS, open System Settings → Displays and select the highest Hertz or ProMotion option. If the higher option is missing, switch from HDMI to a DisplayPort cable connected directly to your dedicated GPU.
What is frame skipping and why does it happen?
When you overclock a 60 Hz or 144 Hz monitor to a higher custom refresh rate in NVIDIA Control Panel or CRU, the GPU sends more frames per second, but the monitor's internal scaler may still refresh the panel at its lower native clock and simply throw away every Nth frame. The browser will report the higher Hz, so only a slow-shutter camera photo of the Frame-Skipping Grid can prove whether every frame actually reaches the glass.
Why does my iPhone or MacBook Pro ProMotion screen show 60 Hz in Safari?
Safari intentionally throttles standard web animations to 60 Hz to extend battery life, even while scrolling runs at 120 Hz. Testing in Chrome on macOS or disabling Safari's "Prefer Page Rendering Updates near 60fps" developer flag reveals the full 120 Hz refresh rate.
Is 144 Hz vs 240 Hz noticeable?
Going from 60 Hz (16.67 ms per frame) to 144 Hz (6.94 ms) cuts frame time by 9.7 ms—a dramatic jump everyone notices even when dragging windows. Going from 144 Hz to 240 Hz (4.17 ms) saves another 2.8 ms, which is most noticeable when tracking fast targets in competitive shooters, especially on OLED panels with near-instant pixel response.
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