Flicker Test
Detect PWM dimming flicker that causes eye strain and headaches. Adjustable brightness patterns expose invisible flicker on monitors, phones, and TVs.
Why use this motion tool
Brightness sweep patterns
Display patterns at 10%, 25%, 50%, 75%, and 100% brightness to surface PWM flicker at common low-brightness settings.
Stroboscopic test
Moving finger or pencil across the screen reveals flicker via the stroboscopic effect — visible broken edges indicate PWM.
Phone camera test
Point your phone camera at the screen; visible banding or rolling lines confirm PWM dimming.
Reference flicker-free indicator
DC-dimmed and OLED displays show no flicker; PWM-dimmed LCDs show clear patterns.
What is motion
Flicker is rapid brightness fluctuation in a display, often invisible to the eye but causing eye strain, headaches, and fatigue over time. The most common cause is PWM (pulse-width modulation) dimming, which dims the backlight by turning it on and off rapidly rather than reducing current.
PWM dimming is cheap and preserves color accuracy at low brightness, but it produces flicker at frequencies between 100Hz and 1000Hz. Some people are highly sensitive to flicker below 200Hz; others notice nothing below 1000Hz. The ICNIRP has warned that long exposure to low-frequency flicker is a health hazard.
DC dimming is the alternative — reducing the actual current to dim the backlight. DC dimmed displays are flicker-free but may shift color at very low brightness. OLED displays use DC dimming at high brightness and PWM at low brightness, which is why some OLEDs flicker only when dimmed. Modern OLEDs use high-frequency PWM (1920Hz+) that's effectively flicker-free.
How to test
Step 1: Dim the room
PWM flicker is more visible in low ambient light. Test in a dim room with the display at low brightness.
Step 2: Set low brightness
Set your display to 25% or lower brightness — this is where PWM is most aggressive.
Step 3: Wave a finger
Wave your finger rapidly between your eye and the screen. Distinct silhouettes indicate PWM flicker; smooth motion indicates DC dimming.
Step 4: Phone camera test
Open your phone camera and point it at the screen. Visible banding or rolling lines confirm PWM.
Step 5: Test multiple brightness levels
Some displays flicker only at low brightness. Test at 100%, 50%, 25%, and 10% to map the flicker pattern.
Common causes of motion issues
PWM dimming
Cheap LCDs dim by pulsing the backlight on and off. Low frequencies (under 200Hz) cause noticeable eye strain.
Low-frequency OLED PWM
Some OLED phones use 240Hz PWM at low brightness, visible to sensitive users. Premium OLEDs use 1920Hz+ or DC dimming.
Inverter-based backlights
Older CCFL-backlit monitors flicker at the inverter frequency (50-100kHz), usually invisible but audible as a whine.
Refresh rate beat frequencies
Mismatched refresh rate and lighting frequency (e.g., 60Hz display under 50Hz fluorescent light) produces visible beat flicker.
Frequently asked questions
Testing tips
- Test at 25% brightness or lower — that's where PWM is most aggressive.
- Use your phone camera to detect PWM — visible banding confirms flicker.
- Look for "Flicker-Free" or "DC Dimming" in monitor specs to avoid PWM.
- If you get headaches from your monitor, PWM may be the cause — test before replacing.
Related tools
PWM Dimming: Why Your Monitor Might Be Causing Eye Strain
Your eyes hurt after a long day at the computer. You blame screen time, blue light, or your prescription. But the real culprit may be invisible: PWM flicker. Many monitors — especially older or budget models — dim their backlight by pulsing it on and off rapidly. Your eyes can't see the flicker, but your brain perceives it, and the result is eye strain, headaches, and fatigue.
PWM (pulse-width modulation) dimming works by switching the backlight between fully on and fully off, hundreds or thousands of times per second. At 100% brightness, the backlight is always on. At 50% brightness, it's on half the time and off half the time. At 25% brightness, it's on a quarter of the time and off three quarters. The brightness appears reduced because the eye averages the on-off pattern over time.
The problem is the off periods. At low brightness, the backlight is mostly off, producing long dark periods that the eye perceives as flicker — even if you don't consciously see it. PWM frequencies below 200Hz are noticeable to most people; frequencies below 100Hz are unbearable. Some budget monitors use 175Hz PWM, which is borderline; premium monitors use DC dimming (continuous current) or PWM above 3000Hz, which is effectively flicker-free.
Test your display with our flicker test. Set your monitor to 25% brightness or lower — that's where PWM is most aggressive. Wave a finger rapidly between your eye and the screen. If you see distinct silhouettes of your finger (like a strobe light), your display uses PWM. If your finger appears as a smooth blur, your display is flicker-free. Confirm with your phone camera: point it at the screen and look for visible banding or rolling lines.
If your monitor flickers, the only real fix is to replace it. Look for "Flicker-Free" or "DC Dimming" in the spec sheet. Most modern IPS and VA monitors are flicker-free; budget TN panels and some OLEDs at low brightness may not be. OLED phones are particularly variable — premium models like the iPhone 15 Pro use 1920Hz+ PWM or DC dimming, while cheaper OLEDs may use 240Hz PWM that sensitive users can detect.
Don't confuse PWM flicker with refresh rate. A 60Hz monitor refreshes the image 60 times per second, which is visible as motion blur but not flicker. PWM flicker is a property of the backlight, not the LCD panel. A 144Hz monitor with low-frequency PWM is still bad for your eyes. Pair the flicker test with our brightness test and OLED screen test for a complete eye-comfort audit. Your eyes will thank you.
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