Panel & Backlight
PWM Flicker Test
Bright fields and a fast-moving line for the pencil and camera flicker tests.
▶ Start full-screen testWhite← / → or tap the sides to switch · Esc to exit
How to use
- 1Set the screen to the brightness you normally use — PWM usually appears at low brightness.
- 2On the White field, wave a pencil quickly in front of the screen: several crisp copies mean PWM, a smooth blur means flicker-free.
- 3Or point your phone camera at the screen: dark bands rolling across it suggest PWM.
- 4On the Fast moving line (→), follow the line with your eyes: a row of separate lines instead of one smooth streak means PWM.
- 5Press Esc to exit.
FAQ
Can this page detect PWM by itself?
No. A web page can't see your backlight, so the result comes from what you observe — these patterns just make the effects easy to spot. A slow-motion camera or a cheap light sensor gives a definitive answer.
Why does it only show at low brightness?
Many screens dim by switching the backlight off for part of each cycle. At high brightness the off periods are short or absent, so the flicker appears as you turn the brightness down.
Tips
- Repeat at several brightness levels — many screens are flicker-free above about half brightness.
- A screen that only bothers you at night is a strong PWM suspect.
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Related guides
Learn more about what this test reveals and how to act on the results.