Refresh Rate & Frame Skip Test

The refresh rate is how many times a second a screen draws a new picture: 60 Hz, 120 Hz, 144 Hz and higher for gaming monitors. It is on the box and in the settings, but whether your computer actually delivers it, in your browser, is another matter. This test asks the browser for a new frame as fast as the screen allows, times the gaps and reports the refresh rate, its steadiness and the frames that were late.

How the measurement works

Browsers draw animations in step with the screen. The page asks for an animation frame, notes the time, asks again, and does this for five seconds. The median gap between frames gives the refresh rate: a gap of 16.67 ms is 60 Hz, 6.94 ms is 144 Hz. The result is compared with common values (24, 30, 48, 50, 60, 72, 75, 90, 100, 120, 144, 165, 180, 240, 360 and 480 Hz) and the closest is shown. A frame that takes more than 1.5 times the median counts as late.

A worked example

Press Sample to load a demonstration of a 144 Hz display: 700 frames at 6.94 ms, one frame that took three times as long and one that took twice. The page reports 144.0 Hz, a median frame time of 6.94 ms, a longest frame of 20.8 ms and 2 late frames out of 700, which is 0.29 percent. The jitter figure is the spread of the gaps. Run it for real with the button, and a typical 60 Hz screen gives a rate near 60 Hz with a frame time around 16.7 ms.

The moving bar

During the test a bar glides across a lane at a constant speed in pixels per second. If frames are dropped, the bar visibly jumps. Choose Slow, Medium or Fast: at a higher speed each missed frame covers more distance, so faults are easier to see. The bar is a visual check, and the numbers are the measurement.

Why the result can be lower than expected

Browsers limit animation to the refresh rate of the screen they are on. A 144 Hz monitor reads 60 Hz if the system is set to 60 Hz, if the display cable or adapter cannot carry more, if the window is on a second slower monitor, or if battery-saver mode lowers the rate. Variable refresh rate (G-Sync or FreeSync) and power saving can give a rate that is not close to a standard value, and the page says so.

Late frames

A few late frames are normal, for example when the page starts. More than 2 percent of frames being late triggers a warning: close other tabs and applications, plug in a laptop and run the test again before blaming the screen. Keep the tab in front, because browsers slow background tabs, and do not scroll during the test.

Edge cases

On a phone, the browser may cap animation at 60 Hz even when the screen runs at 120 Hz, depending on its settings. External monitors on a laptop can differ from the built-in screen. The five-second sample is short, so intermittent stutters may not appear; run the test several times.

Limits

It measures when the browser presents frames, not the response time of the panel, the input lag of the system or the real hardware rate when the browser is capped. Results are not saved or sent.

Related tools

• Dead Pixel Test checks the display for faulty pixels and uniformity.
• Mouse Test measures the polling rate of the mouse.
• Aim Trainer shows how reaction time depends on the whole chain.
• Stopwatch times anything else you need to time.