How to test a new monitor

Test a new monitor the day it arrives, while you can still return it. The check takes about 10 minutes in your browser and also works for a laptop, a TV or a used monitor.

Before you start

1. Clean the screen with a dry microfiber cloth. Dust can look like a dead pixel.
2. Let it warm up, ideally for about 30 minutes, before you judge uniformity or color. Both can shift as the panel warms.
3. Set the native resolution and refresh rate. In Windows 11, open Settings > System > Display and pick the resolution marked (Recommended), then choose the rate under Advanced display > Choose a refresh rate. On a Mac, both are in System Settings > Displays.
4. Turn off picture adjustments such as Night light, Night Shift, True Tone, and the monitor’s eco or dynamic contrast mode.
5. Set browser zoom to 100% and dim the room.

Run the 10-minute check

Go in this order. Most tests fill the screen; press Esc to leave.

1. Solid colors (1 minute). In the Monitor Test, press Start test and step through the colors. Check the whole panel, edges included, for a tint on white, dark bands or odd patches.
2. Dead and stuck pixels (2 minutes). In the Dead Pixel Test, press Start test and scan each color section by section; Auto cycle changes the color every 3 seconds. A dot that stays black on every color is dead, one that stays a single color is stuck, and one that stays bright on black is hot. Note where each one is.
3. Backlight bleed (1 minute). In a dim room at your usual brightness, view the black and near-black levels of the Backlight Bleed Test from straight on, then from the sides. Light that shifts with the angle is IPS glow; light that stays put is bleed. Skip this on an OLED, which has no backlight.
4. Uniformity (1 minute). On the fields of the Screen Uniformity Test, look for dark corners, pressure marks, cloudy patches or a tint that changes across the screen.
5. Banding (1 minute). The gray ramp in the Gradient Test should look smooth. Faint, even steps are normal, because web pages generally have 256 levels per color channel; coarse bands or colored stripes are not.
6. Gamma and shadows (1 minute). On the Gamma chart in the Gamma Test, step back until the stripes blur and find the patch that blends into its surround. Most monitors aim for about 2.2. On Shadow detail, most bars should stand out from black; the lowest one or two blending in is common.
7. Refresh rate (1 minute). In the Refresh Rate Test, press Start measuring and keep the tab in front for 3 seconds. The result estimates how often your browser draws. If a 144 Hz monitor reads 60 Hz, check the refresh rate setting, the cable and the port: some monitors reach their top rate only on DisplayPort or one HDMI port.
8. Motion (2 minutes). In the Ghosting Test, follow the moving shapes at a few Speed settings, with and without Invert. Some blur is normal on every display. For long trails or a bright or dark halo, try each level of the monitor’s overdrive setting (often called Overdrive or Response Time) and keep the cleanest.

What is normal and what is a defect?

Most LCDs show some glow or bleed on black in a dark room. What matters is whether you notice it in normal use.

What you see	Usually	What to do
Corner glow that shifts as you move your head	IPS glow, normal on IPS panels	Nothing
A little light at an edge, only on black in a dark room	Mild bleed, common on LCDs	Nothing, unless you notice it in normal use
Bright patches in dark scenes at normal brightness	Strong backlight bleed	Ask the seller about a return or exchange
Edges slightly darker than the center	Normal, most visible on large LCDs	Nothing
Cloudy patches, or a tint that shifts across the screen	Clouding or poor uniformity	Report it if visible in normal use
A dot that stays black on every color	Dead pixel	Count it and check the pixel policy
A dot stuck on one color, or lit on black	Stuck or hot pixel	Try the Stuck Pixel Fixer
A line of pixels, or a dark spot that grows	A panel or connection fault, or damage	Return it or make a claim

Never press on the panel or loosen the bezel to reduce bleed. It can damage the screen.

Why photos make bleed look worse

In a dark room, a phone camera raises its exposure, so a faint glow becomes a bright blotch, and a shot from an angle adds glow you cannot see from your chair. Judge with your eyes. If you need a photo for a return, lower the camera’s exposure until it matches what you see.

What to do if you find a fault

1. Rule out dust and the computer: clean the screen, then try another cable or port, or the built-in self-test below.
2. Note what you saw, where, and at which settings. The dead vs stuck pixel guide shows how to tell pixel faults apart and record them.
3. Contact the retailer while the return window is open, and keep the box. A return is often simpler than a warranty claim.
4. For a warranty claim, read the manufacturer’s pixel policy for your model; policies differ between makers and product lines. No software repairs a dead pixel.

How to use a built-in self-test

Some monitors can show test patterns of their own from a diagnostics item in the on-screen menu; check your manual. A monitor’s own menu and its “No signal” message are drawn without the computer too. If those look clean but your computer’s picture does not, suspect the cable, port, driver or settings rather than the panel.

Laptops have self-tests too. Dell documents an LCD built-in self-test: hold the D key, press the power button, and keep holding D until colors appear. The screen then cycles through black, white, red, green and blue. For other makers, search their support site for your model’s diagnostics. Many TVs have a picture test in the support or settings menu.

How to test a laptop screen

1. Plug in the charger. Some laptops drop to 60 Hz on battery.
2. Run the 10-minute check, then the maker’s built-in test.
3. On a white or gray field, tilt the lid slowly. Flicker or lines that follow the hinge can point to a display cable problem.
4. Connect an external monitor if you have one. If it looks right, the laptop’s panel or its cable is the likely cause.

For the rest of a second-hand laptop, see the used laptop checklist.

How to test a TV

1. Open this site in the TV’s browser, or connect a laptop over HDMI and move the browser window to the TV.
2. Turn off overscan in the picture size settings so the whole picture fits the screen; the name varies by brand. The Overscan pattern in the Screen Geometry Test shows whether the edges of the picture are cut off.
3. Test in the picture mode you will use. Motion smoothing, dynamic contrast and local dimming change what the tests show.

How to check a used monitor before you buy

A private sale often has no returns, so test before you pay.

1. Bring a laptop and a cable that fits.
2. With the monitor off, check the screen under a light for scratches and cracks.
3. Run at least the Monitor Test, Dead Pixel Test and Backlight Bleed Test from each input you plan to use.
4. On an OLED, look for faint logos, taskbars or bands on the gray fields of the Screen Burn-In Test.
5. Try every button, the menu and the stand.

What a browser cannot check

A web page draws patterns but cannot read the monitor, so it cannot check:

• Brightness in nits or the contrast ratio, which need a light meter or colorimeter.
• Color accuracy, which needs a colorimeter.
• Response time in milliseconds or input lag, which need measuring equipment.
• Flicker (PWM) frequency.
• The model, serial number or panel type.
• 10-bit color. Web pages are generally drawn at 8 bits per channel, so a gradient cannot prove it.

For those, look for reviews of your model that publish instrument measurements.