Refresh rate test
Measure the refresh rate your browser is actually getting, and see whether variable refresh is active.
This measures the rate your browser is receiving frames at, which is not always your monitor's configured rate. A browser window on a secondary display, a laptop on battery saver, or a frame rate limiter will all show up here as a lower number.
How the measurement works
Browsers fire a callback once per display refresh. The test records the time between those callbacks for two seconds, then takes the median interval and converts it to a rate.
The median matters. One dropped frame during the sample moves an average significantly while barely touching a median, so an average would routinely under-report. The first few frames are also discarded, since the browser is still settling when a measurement starts.
Reading the jitter figure
Jitter is the spread between the fastest and slowest frames, ignoring the extreme five percent at each end. On a fixed rate display it is small, usually well under a millisecond.
A large spread almost always means variable refresh is active. G-Sync and FreeSync change the display rate continuously to match what is being rendered, so there is no single correct answer and the reported figure is an average over the sample.
When the number is lower than expected
Check which display the window is on
The browser runs at the refresh rate of the display the window is on. A window dragged to a 60Hz secondary monitor reports 60Hz regardless of what your main panel can do.
Check your display settings
High refresh monitors frequently ship set to 60Hz and stay there until changed manually. This is the single most common reason someone with a 144Hz monitor measures 60.
Check the cable
Bandwidth limits which combinations of resolution and refresh rate are possible. An older HDMI cable can carry 4K at 60Hz but not at 120Hz, and the display silently falls back rather than failing. DisplayPort generally has more headroom.
Check power settings
Laptops commonly drop to 60Hz on battery, and some browsers cap animation frames in low power mode independently of the display. Plug in and retest before looking further.
Common questions
Why does this show a lower number than my monitor is set to?
This measures the rate your browser is receiving frames at, which is not always your monitor setting. A window on a secondary display runs at that display rate, laptops on battery often drop to 60Hz, and browser or GPU frame limiters cap it further. Check your display settings and move the window to your main monitor before concluding anything.
My result keeps changing between runs.
Some variation is normal. Large variation usually means variable refresh is active, where the display deliberately changes its rate. The jitter figure tells you which you are looking at: a fixed rate display holds its frame interval tightly, a variable one does not.
Why is the number not a round figure like 144?
Displays rarely run at exactly their advertised rate. A 144Hz panel typically runs at 143.9 or similar, and measurement over a two second window adds its own small error. Anything within a couple of percent of a standard rate is that rate.
Can I test my refresh rate in a background tab?
No. Browsers stop animation frames entirely in background tabs to save power, so a measurement taken while the tab was hidden is meaningless. The test detects this and discards the result rather than reporting a wrong number.
Does the browser limit my refresh rate?
It can. Some browsers cap animation frames to 60Hz on battery power or in low power mode, and hardware acceleration being disabled has the same effect. If you get 60Hz on a high refresh display, check your browser settings before suspecting the monitor.
Troubleshooting guides
Test your other hardware
Most hardware faults travel in pairs. If one device is misbehaving, check the rest.