Refresh Rate Test
Time the frames your browser paints and read the rate in Hz. See the live rate, frame-time jitter and a chart. The result is presented frames, not the refresh rate stored by the OS.
At a steady rate the lit cell sweeps evenly. Gaps or doubled cells in a phone photo mean dropped frames.
Keep this tab in front for a couple of seconds.
This times how often the browser paints a frame. It does not read the refresh rate stored in Windows or macOS. Low-power mode, battery saver and some browsers (Safari on some Macs) cap that at 60 Hz even when the screen runs faster, so a low reading is worth another look in Chrome, Edge or Firefox on mains power.
Is your 144 Hz monitor really running at 144 Hz?
How the test works
The page asks the browser for a frame before each paint and times the gap with that callback's timestamp. It skips the first 30 frames, keeps the last 300 gaps, and uses the median, so one stutter does not set the rate. Gaps of 100 ms or more are treated as a stall and left out, and time while this tab is hidden is not counted. A 144 Hz panel is about 6.94 ms per frame, a 60 Hz panel about 16.67 ms. Jitter is the spread of those gaps. The verdict flags it when the spread is more than a quarter of the median, which is common with G-Sync, FreeSync or ProMotion because the spacing can float with the content.
Why it reads 60 Hz
The most common cause is Windows itself: a new monitor often starts at 60 Hz until you change it. Next is the link. HDMI 1.4 tops out around 120 Hz at 1080p and 30 Hz at 4K, and an old or cheap cable can force a lower mode, so use the DisplayPort cable from the box or a certified HDMI 2.1 cable. On many monitors only the DisplayPort input supports the full rate. If the box says 144 Hz and this test stays near 60, the display mode may be 60 Hz, the link may be holding the mode down, or the browser may be painting 60 frames a second on a faster panel. This page cannot see the OS setting.
Setting the rate in Windows and macOS
Windows 11: Settings, System, Display, Advanced display, then Choose a refresh rate. Windows 10 hides it under Advanced display settings. Also check the NVIDIA Control Panel (Change resolution) or AMD Software (Display), which can override it. On macOS open System Settings, Displays, and pick the rate in the Refresh rate menu. ProMotion MacBooks vary between 24 and 120 Hz on their own, and Safari may hold pages at 60 Hz unless you turn off the Prefer Page Rendering Updates near 60fps feature flag.
Laptops and power saving
Many gaming laptops drop to 60 Hz on battery, and Windows battery saver or Chrome energy saver can throttle animation frames too. Plug in, close other heavy tabs and run the test again. If the resolution looks wrong as well, the GPU may be driving the screen in a fallback mode.
Related tools
Check a new screen for stuck pixels with the dead pixel test and image retention with the burn-in test, confirm your resolution with the screen resolution test, or see if your mouse keeps up with a fast panel using the mouse polling rate test. Then put the whole chain to work with the F1 reaction test.
Frequently asked questions
Is this monitor Hz or browser FPS?
It is the rate of frames the browser paints, in Hz. That tracks the display refresh while this tab is visible and the browser is not capping animation. It is not the refresh rate stored in Windows or macOS display settings.
Why can a 144 Hz panel show about 60 here?
The panel may still be set to 60 Hz in the OS or the GPU control panel. An older HDMI port or cable can also force a lower mode, and many laptops drop to 60 Hz on battery. Battery saver and some browsers, including Safari on some Macs, can paint at 60 Hz even when the screen is faster. The number here is presented frames, so check the OS rate and try Chrome, Edge or Firefox on mains power.
Does the tab have to stay visible?
Yes. Browsers slow or stop animation frames in a background tab, and those gaps are not the monitor rate. This page stops sampling while the document is hidden, throws out that window, and starts again when you come back. Leave the tab in front for a couple of seconds.
Why do I see a dash instead of 0 Hz?
One frame is not a result, and an empty sample is not 0 Hz. The page skips the first 30 frames, then waits for at least 30 gaps. Until then the readout is a dash. The rate is the median of the latest 300 gaps. A gap of 100 ms or more is treated as a stall and left out.
Can this measure pixel response time or 8000 Hz?
No. It only times presented frames. It does not measure how fast a pixel changes color, input lag, or a refresh mode the browser never paints.
Why does the rate wobble, and what is jitter?
Jitter is how spread out the frame gaps are. The verdict flags it when that spread is more than a quarter of the median gap. G-Sync, FreeSync and ProMotion let the spacing move with the content, so some wobble is normal. If the reading is within about 4 percent of the rate you picked, it counts as that rate. That covers 59.94 Hz panels and timer rounding.