DeviceCheck Pro

Refresh rate test

How many times per second does your screen actually redraw? The test starts automatically and settles within a couple of seconds. Keep this tab in front.

Display timing
IdleTestingPassFault
…Hz
–measured Hz (unrounded)
–ms per frame
–timing jitter (ms)
0late frames in last ~4 s

Frame times: even bars mean smooth delivery; tall red bars are late frames.

Explainer

What more hertz actually buys you

A screen doesn’t show motion; it shows a quick series of still frames. Between two refreshes a moving object jumps. The faster it moves, the bigger the jump, and the jumps are what your eye reads as stutter or blur.

Below, each mark is where an object moving across a 1,920-pixel-wide screen gets drawn during 100 ms. Compare two refresh rates.

6 frames in 100 ms · jump of 20 px per frame · 16.7 ms between frames

14 frames in 100 ms · jump of 8 px per frame · 6.9 ms between frames

Common refresh rates

RateFrame timeWhere you find it
60 Hz16.7 msMost office monitors, older phones, many TVs
90 / 120 Hz11.1 / 8.3 msRecent phones and tablets, many laptops and TVs
144 / 165 Hz6.9 / 6.1 msMainstream gaming monitors
240 Hz and up4.2 ms or lessEsports monitors

Refresh rate affects how quickly a change can appear on screen, which shows up directly in the reaction time test. While you’re checking a monitor, run the dead pixel test too.

Still not working? Describe it

An AI assistant suggests likely causes and fixes, cheapest first. It sees only what you type. Answers can be wrong; check your device maker’s support pages before opening anything up.

Questions

How does this refresh rate test work?

Browsers draw animation in step with the screen: requestAnimationFrame fires once per display refresh. The page timestamps those callbacks for a few seconds and converts the average gap into hertz, then rounds to the nearest common rate.

My 144 Hz monitor shows 60 Hz. Why?

The operating system is probably set to 60 Hz. On Windows: Settings → System → Display → Advanced display → Choose a refresh rate. On macOS: System Settings → Displays → Refresh Rate. Also check the cable: older HDMI versions and some adapters can’t carry high refresh rates at full resolution. Laptops on battery often drop to 60 Hz to save power.

Why does the reading jump around?

Background tabs, power-saving modes, variable refresh rate (FreeSync, G-Sync, ProMotion) and a busy CPU all disturb timing. Keep this tab in front, plug in your laptop and let the test run for a few seconds. Variable-rate screens may idle at a lower rate until something moves.

Does iPhone Safari show 120 Hz?

Safari on iPhone has historically limited web page animation to 60 Hz even on ProMotion displays, unless a setting in Safari’s advanced feature flags is changed. So a 60 Hz reading there is a browser limit, not a fault.

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