PWM Flickering-How to Check If Your Screen Causes Headache
PWM flickering is the rapid on-off switching some screens use to control brightness. You usually can’t see it, but at low brightness it can cause eye strain or headaches in sensitive people. You can test for it in a couple of minutes with a phone camera, and you can reduce it by changing your brightness settings or choosing a flicker-free display. If you’re seeing a visible flicker instead, read our monitor flickering guide.
Table of Contents
What is PWM Flickering?
PWM stands for pulse-width modulation. Instead of lowering the power to the backlight smoothly, the screen switches the light on and off many times per second. A shorter “on” time looks dimmer, and a longer “on” time looks brighter. Your eyes blend the pulses into a steady image, so you see a dim screen and not a flashing one.
Many LED-backlit monitors and laptops use PWM, and OLED phone and laptop panels commonly use a similar method at low brightness. It’s popular with manufacturers because it keeps color accurate and is cheap to build.
The key figure is the PWM frequency, meaning how many times per second the light switches on and off. Higher frequencies are generally easier on sensitive eyes, but there isn’t one number that is safe for everyone.
Why PWM Flickering Can Cause Eye Strain and Headaches
Even when you can’t consciously see the flicker, your visual system may still react to it. Some people report eye strain, headaches, dizziness, or fatigue after long sessions on a screen that uses low-frequency PWM, especially at low brightness.
Two points to keep in mind:
- Sensitivity varies. Many people never notice PWM at all. Research and reviewers describe the problem as affecting sensitive users, not everyone.
- PWM isn’t the only cause of screen headaches. Glare, poor posture, dry eyes, wrong prescription glasses, and long hours without breaks all contribute. If headaches persist, see a doctor or an eye specialist, particularly if you have migraines or a light-sensitive condition.
PWM Flickering vs. Normal Screen Flickering
They look like the same problem, but they aren’t.
| PWM flickering | Normal screen flickering | |
|---|---|---|
| Visible? | Usually not | Yes, you can see it |
| Cause | Brightness control method (by design) | Cable, driver, refresh rate, or hardware fault |
| When it happens | Mostly at lower brightness | Often random or constant |
| Fix | Change brightness settings or choose a different display | Troubleshoot or repair |
If you can see the screen flashing, jumping, or showing lines, follow our monitor flickering fixes. If you’re on a laptop, see our laptop screen flickering guide.
How to Check If Your Screen Uses PWM
You don’t need special equipment. Try these in order.
1. The phone camera test
- Set your screen to low brightness (around 10 to 30%) and display a plain white or light-gray page.
- Open your phone’s regular camera in video mode and point it at the screen.
- Watch the preview or record a few seconds.
- If you see dark horizontal bands or a rolling shimmer on the screen, PWM is a strong possibility.
- Raise the brightness to 100% and check again. Many screens stop showing bands at full brightness.
A caution: this test isn’t conclusive. Camera frame rates and shutter speeds can create bands on a screen that uses little or no PWM, and some PWM is too fast for the camera to catch. Treat it as a hint, and confirm with a review.
2. The hand-wave test
In a dim room at low brightness, wave your hand or a pen quickly in front of a bright area of the screen. If you see a series of separate “ghost” images instead of a smooth blur, the backlight is probably pulsing.
3. Check independent reviews
This is the most reliable method. Some review sites measure PWM with lab equipment and list the frequency and the brightness level at which it appears. Notebookcheck’s laptop reviews, for example, state whether PWM was detected and under which brightness setting. Search your model’s name plus “PWM” before you buy or return something.
How to Reduce PWM Flickering
You can’t remove PWM from a display that uses it, but you can often reduce its effect.
- Keep brightness higher. On many screens, PWM only appears below a certain brightness level. Stay above it and flicker may disappear.
- Reduce glare another way. If you’re turning the brightness down because the screen is too bright, dim the room lights or use a lamp behind the screen instead, so you can keep the screen’s own brightness higher.
- Look for a built-in setting. Some phones and monitors include a “DC dimming,” “flicker-free,” or “high-frequency PWM” option in the display settings or on-screen menu. Check yours.
- Try dark mode and a software dimming overlay. These can lower the amount of light reaching your eyes without lowering the backlight, though how much they help varies by person and device.
- Take regular screen breaks. Looking away for a short time every 20 minutes or so helps with eye strain from any cause.
- Switch to a flicker-free display if nothing else works (see below).
PWM vs. DC dimming
DC dimming lowers brightness by reducing the electrical power sent to the backlight, so the light stays on continuously instead of pulsing. Displays that use it are often marketed as flicker-free and tend to be more comfortable for people sensitive to PWM.
Some displays use a hybrid approach, with DC dimming at some brightness levels and PWM at others. That’s why a single spec line on a product page rarely tells the whole story.
Before you buy:
How to Choose a Flicker-Free Monitor or Laptop
- Read an independent review that measures PWM, and check the frequency and the brightness at which it occurs.
- Look for “flicker-free” labeling or a DC dimming mention, but don’t treat the label as proof. Manufacturers use the term differently.
- Check the return policy. If you’re sensitive, the real test is a few days of normal use.
- Ask in owner communities for your specific model, since people with PWM sensitivity are quick to report problems.
If you’re also choosing a screen shape, our curved vs flat monitor guide covers that side of the decision. For connections and cables, see our HDMI vs DisplayPort guide.
Frequently asked questions
How do I know if my monitor uses PWM?
Search your model name plus “PWM” in an independent review, or try the phone camera test at low brightness. Dark bands in the video suggest PWM, but they’re not proof.
Does PWM flickering really cause headaches?
For some people, yes. Many users never notice it, while sensitive users report eye strain, headaches, and fatigue, especially at low brightness. The effect differs from person to person, and screens aren’t the only cause of headaches.
Is PWM flicker harmful to your eyes?
There’s no widely accepted evidence that PWM permanently damages healthy eyes, but it can cause discomfort and strain in sensitive people. If you have migraines, epilepsy, or another light-sensitive condition, ask your doctor.
Why do my eyes hurt at low brightness but not at high brightness?
Many screens use PWM mostly at lower brightness levels. At higher levels the light is on for longer or continuously, so the flicker is less pronounced or gone.
Can I turn off PWM on my monitor or phone?
Some devices have a DC dimming or flicker-free setting in the display menu. Others have no option, in which case keeping brightness higher is the best workaround.
What PWM frequency is safe?
There’s no single safe number. Higher frequencies are generally more comfortable, but sensitivity varies, so independent reviews and your own testing matter more than one figure.
Is PWM the same as a flickering screen?
No. PWM is a brightness-control method that happens too fast to see. A visibly flickering screen is a fault or setting problem. See our monitor flickering fixes for that.
Do OLED screens use PWM?
Many OLED phone and laptop screens do, particularly at low brightness. Check phone settings and reviews for your specific model, since some offer a high-frequency or flicker-reduction option. Android Central’s PWM explainer is a good reference for phones.
Can a flicker-free monitor still cause eye strain?
Yes. Glare, brightness that’s too high or too low, poor posture, and long sessions without breaks can all cause strain even on a screen with no PWM.
Conclusion
PWM flickering is a brightness-control method, not a fault, and many people never notice it. If you get headaches or eye strain at low brightness, it’s worth ruling out. Run the phone camera test, check an independent review for your model, and try keeping the brightness higher while managing glare with room lighting.
If it still bothers you, choose a display with DC dimming or a high PWM frequency, and use a good return policy to test it. If you’re seeing visible flashing instead, work through our monitor flickering guide, and if headaches continue, speak with a doctor
