How to check a monitor for brightness pulsing

Your monitor gets brighter and darker even though you have not touched the controls. The change may happen all the time, only in a dark room, or when a video or game is on screen. A few comparisons can help you narrow down whether the cause is the monitor, the computer, or the connection between them.

The Display Test can show colors and check the display's refresh rate. It cannot measure backlight flicker or brightness with a sensor, so use it to create a steady image and observe what happens.

Check for brightness pulsing

1. Open the Display Test on the monitor that appears to pulse. If you have more than one screen, make sure the test is on the one you want to inspect.
2. Use the color test to show a steady color. Watch the screen for 30 seconds from your usual viewing distance. Avoid staring at any pattern that feels uncomfortable.
3. Repeat with a few different colors, then compare the test with a plain page or desktop background. Keep the room lighting and your viewing angle the same.
4. Note when the pulsing happens. Does it affect the whole screen, only dark scenes, only video or games, or only after the monitor has been on for a while?
5. If possible, connect the monitor to another computer, or try a different cable and port. Change one thing at a time so you can tell which change affects the symptom.

For a useful comparison, leave the monitor's brightness setting unchanged during the first checks. If you change several display settings at once, it becomes harder to identify the cause.

What the result means

The image pulses on the color test and desktop

If the whole screen visibly brightens and dims on steady images, the cause may be a monitor setting, its power supply, the cable, or the display hardware. Try the fixes below, then compare with another computer or cable.

It happens only in dark scenes or certain content

Automatic contrast, local dimming, or content-based brightness may be changing the image. Some monitors dim parts of the screen to improve contrast. HDR video and games can also look different from a plain desktop. Check the monitor's picture settings and the computer's brightness or HDR settings.

It happens only when a video or game is running

The application, graphics driver, or a variable refresh setting may be involved. Test a different video or game, then try a steady desktop image. A result that follows one application points away from a general monitor fault.

The Display Test looks steady, but the screen still seems to pulse

The problem may be intermittent or tied to content that the test does not reproduce. Check whether the room lighting is changing, and look for a brightness control that responds to ambient light. A browser test can show the image, but it cannot measure rapid changes in the monitor's backlight.

How to fix it

1. Check the monitor's picture settings. Use the monitor's physical buttons or on-screen controls to turn off settings with names such as dynamic contrast, automatic brightness, eco mode, or local dimming, if available. The names vary by model. Test after changing one setting.
2. Turn off automatic brightness changes. On Windows 11, open Settings › System › Display › Brightness. If your device offers Change brightness based on content or automatic brightness based on lighting, turn it off for a comparison. On macOS, open System Settings › Displays and turn off automatic brightness or True Tone if those options appear. External monitors may use their own controls instead.
3. Compare with HDR off. On Windows 11, open Settings › System › Display › HDR and turn off HDR temporarily if it is enabled. On macOS, open System Settings › Displays and check the display's available dynamic range options. If pulsing stops, the change is related to HDR or how the content is being displayed, rather than necessarily a failed screen.
4. Set a fixed refresh rate. On Windows 11, open Settings › System › Display › Advanced display and select a standard refresh rate supported by the monitor. On macOS, open System Settings › Displays and choose a fixed refresh rate if the option is available. This is a comparison, not a direct test of brightness flicker. The Display Test's refresh rate check does not measure backlight pulsing.
5. Reconnect the display. Turn off the monitor, reseat both ends of its video cable, and try another compatible cable or port. A loose or damaged connection can cause brief changes, flickers, or dropouts that may look like pulsing.
6. Restart and update the computer. Restart the computer, then install available operating system and graphics driver updates. If the issue began right after an update, test the monitor with another device before changing or rolling back drivers.

When the monitor may need repair

If the pulsing continues on a steady image after you disable automatic picture adjustments, and it also happens with a different cable and another computer, the monitor itself is a stronger suspect. Check whether it changes when the monitor is cold versus after it has been on for a while. Do not open the monitor: its power components can be dangerous even after it is unplugged. If it is under warranty, contact the manufacturer. Otherwise, ask a repair shop for an estimate before paying for a repair, especially if the monitor is older or inexpensive.

Why a phone camera can show flicker that you cannot see

A phone camera may show moving dark bands when pointed at a monitor, even when the screen looks steady to your eyes. The camera captures the image line by line, and its timing can conflict with the monitor's refresh or backlight timing. That can create bands in the recording that are not visible flicker. Treat a camera recording as a clue, not proof of a fault. A specialized flicker meter is needed to measure rapid brightness changes reliably.