Monitor Flicker Test: How to Check Your Screen

Quick answer: A monitor flicker test checks whether your screen brightness pulses or shimmers. Start with a camera in slow motion, then view solid color screens at several brightness levels. Watch for bands, shimmer, or eye discomfort. If you see signs, check settings and cables before you blame the panel.

Some flicker is easy to see. Some is too fast for your eyes, yet your eyes may still feel tired after a long day. A simple monitor flicker test at home can show you where to look next.

This guide explains what flicker is, how it differs from refresh rate and signal faults, and how to run a clear monitor flicker test with your phone and a few solid colors.

What is monitor flicker?

Flicker is a change in screen brightness over time. The change can be slow and obvious, or so fast that you only sense it as a shimmer or as tired eyes.

A good monitor flicker test starts by separating three things that often get mixed up. Each has a different cause and a different fix.

PWM backlight flicker

Many monitors dim their backlight by switching it on and off very quickly. This method is called pulse-width modulation, or PWM. The longer the light stays off in each cycle, the dimmer the screen looks.

Some sources note that PWM flicker is often more of a concern at low brightness settings. A monitor sold as flicker-free should hold the backlight steady instead. Still, a label does not guarantee comfort for every person, so test your own screen.

Refresh rate

Refresh rate is how many times per second the display updates the image. It is measured in hertz (Hz). It affects motion smoothness. It is not the same as backlight flicker.

A wrong or unstable refresh rate can still make a screen look unstable, so it is worth checking. We cover that below.

Signal and software faults

A loose cable, a weak port, a graphics driver problem, or a game feature can all cause a flicker-like effect. Features such as variable refresh rate, blur reduction, strobing, and HDR can also change how the screen behaves.

If the problem appears only in one app or one game, it is probably not a panel fault.

How to run a monitor flicker test with a phone camera

Your phone camera can reveal pulsing that your eyes miss. Treat the result as a clue and not as proof.

1. Set up a steady image. Open a plain white page, or a white screen in fullscreen.
2. Start at full brightness. Raise your monitor to its highest level.
3. Point the camera at the screen. Hold the phone steady, or rest it on a stand. Look at the live preview.
4. Lower brightness in steps. Drop the brightness slowly while you watch the preview for rolling dark bands or pulsing.
5. Record slow motion. Switch the camera to slow motion video, record ten seconds at each level, and play it back.
6. Write down the levels. Note which brightness settings, if any, show bands.

If flicker or banding grows stronger as brightness drops, the monitor may be using PWM dimming. If you see nothing, that does not prove the screen is flicker-free. Cameras can miss flicker, so treat banding as a warning sign and not as proof.

Why professionals use instruments

Review labs use a light sensor to measure it. The monitor reviewer RTINGS, for example, measures image flicker frequency with a specialized photodiode tool at several backlight levels. Your phone cannot match that. It can still tell you whether a deeper check is worth doing.

A full-screen solid color monitor flicker test

This second method needs no phone. It uses your eyes and a plain background. Solid colors remove distractions, so shimmer and uneven brightness stand out.

1. Pick a calm room. Dim the room a little, but do not sit in the dark.
2. Open the white screen. Use the white screen tool, press F or double-click, and sit at your normal distance.
3. Test at your usual brightness. This is the level that matters most for daily comfort.
4. Use a brightness ladder. Repeat at 100%, 75%, 50%, 35%, and your preferred night setting.
5. Switch colors. Try the black screen, then red, green, and blue. Some faults show more clearly on one color.
6. Keep each test short. Look for a minute, then rest your eyes. Press Esc when you finish.

Look for visible shimmer, moving bands, a color that seems to pulse, or an edge that crawls. Also note how your eyes feel. If you spot dark corners or uneven glow instead, that is a different issue. See our backlight bleed test.

Test comfort, not only the picture

Some problems show up only after a long session. A short test at high brightness can miss them. For a fairer result, work at your normal setting for 45 to 60 minutes, then log any symptoms.

Repeat on another day or with another display if you can. Compare the results.

Make the monitor flicker test fair

Keep the conditions the same each time. Use the same cable, the same room light, and the same distance. Change only the brightness.

Write short notes after every run. A simple line such as “50%, white, slight shimmer” is enough. Notes turn a vague feeling into something you can compare, and they help if you need to show a seller or a technician.

Symptoms to note during a monitor flicker test

Symptoms alone cannot confirm flicker. Many things cause tired eyes, including long hours, glare, and poor posture. Still, a pattern can point you in the right direction.

• Eye strain: Tired, dry, or uncomfortable eyes after a short time at the screen.
• Headaches: Discomfort that starts during screen use and eases when you stop.
• Blurred or unstable text: Words that seem to shimmer at certain brightness levels.
• Discomfort at one setting: Relief when you raise brightness or use another display.

Take regular breaks and look away from the screen. If symptoms persist, speak with an eye care professional. This guide cannot diagnose a medical problem.

Narrow down the cause after a monitor flicker test

If your test shows something, isolate the cause one step at a time. Change one thing, then repeat the test.

1. Raise brightness. Compare a higher level with your usual one. If flicker fades at a higher level, PWM is a suspect.
2. Turn off extras. Switch off blur reduction, strobing, HDR, and automatic brightness, one at a time.
3. Test variable refresh rate. Turn it on and off in the game or driver that uses it.
4. Check the cable. Reseat both ends. Try another cable or another port.
5. Try another source. Connect the monitor to a different computer. If it flickers there too, the monitor is the likely cause.
6. Try another monitor. If a different display flickers on your computer, suspect the graphics driver or card.

If the cause points to Windows, our guide on how to fix screen flickering on Windows walks through the driver and display steps.

What to do next

• If the monitor flicker test shows nothing: Keep using the screen. Retest if symptoms appear later.
• If one setting causes it: Leave that setting off.
• If it only shows at low brightness: Raise brightness and lower the room lighting, if that is comfortable.
• If it repeats across cables, apps, and computers: Contact the seller about a return or a repair.

When you shop for a new screen, read reviews that measure flicker and check how the monitor behaves at low brightness.

Frequently asked questions

Can I see monitor flicker with my eyes?

Slow flicker is easy to see. Very fast flicker is often invisible, but it may still cause shimmer or discomfort for some people. A camera test can help.

Does a high refresh rate remove flicker?

No. Refresh rate and backlight dimming are separate. A high refresh rate monitor can still use PWM at low brightness, so check both.

Is a monitor flicker test with a phone accurate?

It is a useful screening method, not a measurement. Cameras can miss flicker or add bands of their own, so combine the camera check with a comfort test.

Why does my monitor flicker only at low brightness?

Many monitors dim the backlight with PWM, and the effect can be stronger at lower settings. Try a higher brightness and lower the room light instead.

When should I return a monitor?

Consider a return if discomfort repeats across different cables, apps, and computers. Keep notes from your tests to share with the seller.