How the refresh rate test works
Your screen draws a new picture a fixed number of times a second: its refresh rate, in hertz. Browsers offer pages a callback once per drawn frame, and this test times those callbacks for three seconds once the page has settled. The median gap between frames gives the refresh rate and the frame time; the median is used so one slow frame doesn't skew it.
- Hz is frames per second. The closest standard rate (60, 120, 144, 165, 240 Hz and so on) is shown when the reading is near one.
- Frame time is the time between frames: about 16.7 ms at 60 Hz, 6.9 ms at 144 Hz, 4.2 ms at 240 Hz.
- Jitter is how much frame times vary. Low jitter means smooth, even frames.
- Dropped frames are frames that took more than one and a half frame times, usually because the computer or browser was busy.
- Live keeps counting frames per second while the page is open.
The reading is what your browser gets
This FPS test measures how often your browser draws the page, which usually matches your screen's refresh rate, but not always:
- Battery saver and low power modes can hold the browser to 60 Hz or less. Laptops often do this on battery.
- Background tabs are slowed down or paused. Keep the tab in front while it measures; the test starts over if you switch away.
- Variable refresh (G-Sync, FreeSync, ProMotion on Apple devices) can change the rate with what is on screen, so a reading may sit between standard rates or move a little.
- Several screens at different rates: the browser follows the screen its window is on. Move the window and measure again.
If the result is lower than your monitor's rating, check the refresh rate setting in your system's display settings first. A 144 Hz monitor often starts at 60 Hz until you change it. The cable matters too: older HDMI cables and ports may not carry high refresh rates at high resolutions, while DisplayPort usually does.
The motion test: blur, ghosting and stutter
The three rows show the same flying saucer moving at the speed you choose. The top row moves on every frame, the second on every second frame, the third on every fourth, so you can see your full refresh rate next to half and a quarter of it. This UFO test is in the style of the well-known moving-object tests used to compare screens.
- Smoothness: the top row should look clearly smoother than the bottom one. If they look alike, the screen may be running at a lower rate than you think.
- Motion blur: follow the saucer with your eyes. A soft, smeared edge is normal on most screens and gets less visible at higher refresh rates.
- Ghosting: a faint copy of the saucer trailing behind it comes from slow pixel response. Many monitors have an overdrive setting that changes it; too much overdrive leaves a bright halo instead.
- Stutter: a jerk now and then usually lines up with dropped frames in the reading above.
The objects move smoothly without flashing. Press Pause at any time; if your device asks for reduced motion, the test starts paused.
Questions
How do I check my monitor's refresh rate?
Open this test and keep the tab in front for a few seconds. To change the rate, use your system's display settings: on Windows, Settings, System, Display, Advanced display; on a Mac, System Settings, Displays.
Why does my 144 Hz monitor show 60 Hz?
Usually the refresh rate is still set to 60 Hz in display settings, the cable or port can't carry 144 Hz at your resolution, or the laptop is in a power saving mode.
Is FPS the same as Hz?
Not quite. Hz is how often the screen refreshes; FPS is how many frames a game or app makes. In this test they match, because the browser draws one frame per refresh. In games, FPS above your refresh rate is never fully shown.
Why is the reading a little off, like 143.9 Hz?
Screens run at rates very close to their label rather than exactly on it, and browser timers are rounded slightly. A reading within a few percent of a standard rate is that rate.
Thinking of a faster screen? Our best 240 Hz monitors and the monitor finder are a good start. To check a screen for bad pixels, try the dead pixel test.