heugt.net

Screen Flicker Frequency Tester

Measure frame cadence and calculate the closest whole-frame flicker cycle. Measuring does not flash the screen.

Hz

display cadence
not measured
actual flicker
—
cycle
—
actual − target
—

Measure first. Measurement does not flash the screen.

optional flashing
WARNING: FLASHING LIGHT

Rapid flashing can trigger seizures in people with photosensitive epilepsy. Do not use flashing if you have epilepsy or have ever had a seizure. Stop immediately if you feel dizzy or unwell.

15%

Tap, click, or press any key to stop. Flashing never starts from a shared URL.

A cycle needs at least two frames: one bright and one dark. Actual frequency = measured cadence ÷ frames per cycle. A 40 Hz target on a 60 Hz display resolves to 30 Hz (2 frames); on a 120 Hz display it resolves to 40 Hz (3 frames).

This estimates browser frame timing, not panel PWM, backlight flicker, or a calibrated hardware measurement. Browser throttling, variable refresh, and dropped frames can change the result. Keep the tab visible and re-measure on each display. This is a display experiment, not a treatment.

flashing light

The screen will flash about 40 times a second. This can trigger seizures in people with photosensitive epilepsy. Do not continue if you have epilepsy or have ever had a seizure. Stop immediately if you feel dizzy or unwell.

Tap, click, or press any key to stop.