Refresh rate test
Buying a 144 Hz monitor does not mean you are running at 144 Hz. Windows regularly leaves a new display at 60, and cables and ports quietly cap what they can carry. This measures what the display is actually doing right now, not what the box said.
Not enough frames were drawn to measure. The tab has to be visible and in front — bring this window forward and try again.
- Refresh rate—
- Average frame time—
- Frame stability—
- Skipped frames—
Reading the result
Refresh rate is the median measured value in Hz. Compare it against what your monitor is specified for.
Average frame time is the same number expressed as milliseconds between refreshes: 16.67 ms is 60 Hz, 6.94 ms is 144 Hz, 4.17 ms is 240 Hz.
Frame stability flags whether the intervals were consistent. Uneven results usually mean something else on the machine was competing for the GPU, not that the monitor is faulty. Close other tabs and measure again before concluding anything.
Skipped frames counts intervals long enough that at least one refresh went unpainted.
Run the measurement two or three times. A browser tab is not a controlled environment, and the second run is usually cleaner than the first.
If the number is lower than it should be
Windows 11
- Settings → System → Display → Advanced display. Pick the right monitor at the top if you have more than one, then set Choose a refresh rate to the highest value offered. Windows very often leaves a new monitor at 60 Hz even when it can do far more.
- If the high rate is not offered at all, the cable or port is the limit. DisplayPort is the safe choice for high refresh rates. HDMI 1.4 cannot do 1440p at 144 Hz; HDMI 2.0 cannot do 4K at 144 Hz. A cable that works is not the same as a cable with the bandwidth you need.
- Check which GPU the port belongs to. On a desktop with a discrete card, a monitor plugged into the motherboard is running off the integrated graphics, often at a lower cap.
- Dynamic refresh rate — in the same settings panel — deliberately drops the rate to save power. Turn it off while you measure.
- On a laptop, battery saver caps refresh rate on many machines. Plug it in and measure again.
macOS
- System Settings → Displays. Select the display, then set Refresh Rate to the value you want.
- On a MacBook Pro with ProMotion, the default Adaptive setting varies the rate between 24 Hz and 120 Hz depending on content, so a static page can measure well below 120. That is ProMotion working correctly. To confirm the panel maximum, set the refresh rate to a fixed 120 Hz and measure again.
- External high-refresh monitors over USB-C need a cable rated for the bandwidth. A charging cable that carries video will often only carry it at 60 Hz.
Two monitors, one browser window
The measurement applies to whichever display the browser window is on. If you have a 60 Hz secondary monitor and a 165 Hz primary, drag this window fully onto the fast one before measuring — a window straddling both will give you an answer somewhere between the two, and neither number is meaningful.
Common questions
How does a browser measure refresh rate?
The browser calls back once per screen refresh through requestAnimationFrame, so the gap between callbacks is the refresh interval. We sample for three seconds and take the median gap, then convert it to Hz. The median rather than the average, because a single hitch from another tab would drag an average down by several Hz and report a 144 Hz panel as 130.
Why is the result slightly off, like 143.8 instead of 144?
That is normal and correct. Displays do not run at exactly round numbers — a nominal 144 Hz mode is often 143.98 Hz, and 60 Hz modes are frequently 59.94 Hz for historical reasons. Anything within about half a Hz of the nominal figure is your panel doing exactly what it should.
Why does my 165 Hz monitor measure at 60?
Almost always one of four things: the refresh rate is still set to 60 in the operating system, the cable cannot carry the bandwidth, it is plugged into the wrong port, or the browser window is on a different monitor from the one you think. The steps below work through all four.
Does variable refresh rate affect the result?
Yes. With G-Sync or FreeSync active, the display refresh follows what is being drawn, so a mostly static page can cause the panel to sit well below its maximum. If the number looks low and you have VRR enabled, that is the likely reason — the measurement is accurate, it is just measuring an idle display.
What do skipped frames mean?
A skipped frame is a gap longer than one and a half refresh intervals — at least one refresh went unpainted. A handful over three seconds is normal on a busy machine. Dozens of them means something is competing for the GPU: another tab playing video, a background application, or a browser extension.
Is a browser measurement accurate enough to trust?
For answering am I at 60 or at 144, completely. For distinguishing 144 from 143.5, no — browser timers are deliberately coarsened for security reasons, and the result carries a small amount of jitter. Use it to catch the common misconfiguration, not as an instrument.