PWM Flicker Test
Detect pulse-width modulation (PWM) flicker in your display's backlight. A moving thin white line on black background reveals PWM artifacts.
How to detect PWM
- If the white line appears as a dashed/dotted line, your display uses PWM dimming.
- A solid continuous line means no PWM (DC dimming or high-frequency PWM above perception).
- Lower your monitor brightness to 50% or less - PWM is more aggressive at lower brightness.
- This test works best in a dark room at fullscreen.
Testing guide
How to check PWM flicker
PWM flicker happens when a display dims by rapidly switching the backlight or pixels on and off. Some people are sensitive to this and notice headaches, eye strain, or discomfort at low brightness.
Best for
- Checking whether eye strain appears at lower brightness settings.
- Comparing laptop, phone, OLED, LCD, and external monitor dimming behavior.
- Finding visible flicker bands with a phone camera or visual pattern.
How to run the test
- 1Set the display to the brightness level where discomfort usually happens.
- 2Run the flicker pattern and watch for visible pulsing, shimmer, or banding.
- 3Try filming the screen with a phone camera to reveal rolling bands.
- 4Repeat at higher brightness to see whether flicker reduces or disappears.
How to read the result
More visible bands at low brightness often indicate PWM dimming.
A stable image does not guarantee flicker-free operation, but it is a useful first check.
If symptoms are strong, choose displays advertised as flicker-free or DC-dimmed and verify independently.
Related tools and guides
Frequently asked questions
What is PWM on a monitor?
PWM stands for pulse-width modulation. It dims a display by turning light output on and off very quickly instead of lowering it continuously.
Why is PWM worse at low brightness?
Many displays use longer off periods at low brightness, which can make flicker easier to detect and more uncomfortable for sensitive users.
Can everyone see PWM flicker?
No. Sensitivity varies widely. Some people never notice it, while others feel eye strain or headaches even when flicker is not obvious.