Free PWM Flicker Test Online — Check If Your Monitor Has Backlight Flicker

Use your phone's standard camera app (not portrait mode). Disable auto-exposure if possible — on iPhone enable manual exposure by tapping and locking AE/AF. On Android enable Pro mode. Lower shutter speed (e.g. 1/120s) makes banding more visible.

Use Moving Line first: it needs no camera and works at your display's native refresh rate. If the sweeping bar breaks into several separated copies instead of one smooth blur, your backlight is pulsing (PWM). Use Flicker mode when you want to film the screen with your phone to capture rolling bands.

PWM dimming is typically only active below maximum brightness. At 100% brightness most monitors switch to continuous DC dimming. Test at 50–75% brightness for the most accurate results.

The manual phone camera filming method is most reliable because it directly captures photons from the panel. Automatic webcam detection is experimental and requires a high-framerate camera (120fps+) which most laptop webcams do not have.

For most people, no. Sensitive individuals — particularly those prone to migraines, photosensitivity, or eye strain — may experience discomfort at PWM frequencies below 1000Hz, especially during long work sessions. Choosing a PWM-free or high-frequency (>1000Hz) monitor eliminates this risk entirely.