Frequently Asked Questions

Yes, completely free. Every test, the live screen readings, pixel marking and the report are free, with no limits, no account and no paid tier.

No. Screen Tester runs in any modern browser on Windows, macOS, Linux, ChromeOS, Android, iPhone, iPad and smart TVs. Open the page, pick a test and go full screen.

Because the edges matter most. Browser bars and the taskbar cover the corners and borders, which is exactly where backlight bleed and many dead pixels show up. Full screen puts the pattern on every physical pixel.

Yes, with one limit. Safari on iPhone does not allow true full screen for web pages, so the test fills the whole browser window instead. Turn the phone sideways and set brightness manually for the cleanest result.

About 5 minutes for a quick check, 15 to 20 for everything. White, black and the RGB colors cover pixels in a couple of minutes. Uniformity, gradients, sharpness, motion and touch take the rest.

Only for black and dark grey tests. Backlight bleed and black uniformity need a dim room to be seen. Colors, sharpness and motion are best judged in the light you normally use the screen in.

Any up-to-date browser works. Chrome, Edge, Firefox and Safari all run every test. Chrome and Edge give the most reliable full screen and refresh rate readings on desktop, so use one of them if a test looks wrong elsewhere.

Yes. Drag the browser window onto the second monitor before pressing Full Screen, and the test fills that screen. On a smart TV, open screentester.co in the TV web browser, or mirror a laptop to it with a cable.

Once a test page has loaded, the test itself runs on your device. It does not need to contact our servers while it runs, so a brief drop in connection will not interrupt it. You need a connection to open new pages.

A dead pixel stays black, a stuck pixel stays one color, and a hot pixel stays white. Dead pixels show best on a white screen. Stuck pixels show as red, green or blue dots on black or the opposite color. Hot pixels glow white on every screen.

It depends on the brand, but many follow the ISO pixel fault classes. The common Class II grade allows 2 always-lit, 2 always-dark and 5 sub-pixel faults per million pixels, which is about 4, 4 and 10 on a Full HD screen. Some premium lines promise zero bright pixels, so check your brand's pixel policy and test inside the return window.

A truly dead pixel cannot be fixed with software. The tiny transistor that drives it has failed. A stuck pixel is different and can sometimes be revived with the Stuck Pixel Fixer. Never press hard on the panel, it can damage more pixels.

It sometimes works on stuck pixels and is safe for the screen. It flashes colors rapidly to nudge the sub-pixel back into action, usually over 10 to 30 minutes. It shows a warning first, because fast flashing is not safe for people with photosensitive epilepsy.

Move your head and wipe the screen. Dust and smudges sit on the glass, so they shift slightly against the pattern as you move and come off with a microfiber cloth. A dead or stuck pixel stays in exactly the same spot on every color.

One dead pixel does not usually spread. But a cluster that grows over days, a line of pixels or a dark patch points to a panel or connection fault, which should be reported to the seller or under warranty.

Use Mark mode in the Dead Pixel Test. Go full screen, turn on Mark and tap the dot. The tool logs its exact x and y position, which you can copy or download as a report for a return.

Yes, though it is rare. An OLED pixel can fail and stay dark, or a sub-pixel can stay lit, just like on an LCD. Test a new OLED phone, TV or monitor on white, black and the RGB colors the same way.

Bleed stays put, glow moves. Backlight bleed is light leaking from fixed spots at the edges and looks the same from any angle. IPS glow is a silvery haze in the corners that changes or fades as you move your head or sit further back. Glow is a normal trait of IPS panels; strong bleed is a defect.

Judge it at normal brightness, from your normal seat. Almost every LCD shows some bleed on a black screen in a dark room at full brightness. If you only see it in those conditions, it is usually within spec. If it is obvious in dark movies or games at your usual settings, report it.

Usually not safely at home. Bleed comes from pressure on the panel or gaps in the frame. Loosening screws or pressing the bezel can make it worse and may void the warranty. Lowering brightness reduces how visible it is; a strong case is a return or warranty issue.

Slight variation is normal; obvious patches are not. On flat 50% grey, most screens are a little darker at the corners. Clear pink or green tints, dirty-looking bands or blotches you can see from your seat point to poor uniformity.

Retention fades, burn-in stays. Image retention is a faint after-image that disappears after a few minutes of other content. Burn-in is a permanent ghost of something shown for a long time, such as a taskbar, logo or game HUD.

Mild retention can be cleared; true burn-in is permanent. Run the screen's built-in pixel refresh or panel care routine, which many OLED monitors and TVs also run automatically after use. Pixel shift and avoiding static images for hours at a time help prevent it.

Clouding is soft, blotchy patches of brighter or darker light across a dark screen. It comes from uneven light spread in an LCD backlight and is most common on edge-lit TVs. Check it on 5% and 10% grey in a dim room.

Spread the wear evenly. Keep brightness moderate, use dark mode, auto-hide the taskbar or navigation bar, leave pixel shift and panel care features on, and set a short screen timeout so static images do not sit on screen for hours.

The screen cannot show enough steps of color. Banding is common on 6-bit panels, with heavy video compression, or with limited color settings on the graphics card. Check that your output is set to full range and the highest color depth your screen supports.

Your screen is not running at its native resolution, or it is being scaled. A one-pixel checkerboard only looks crisp when every image pixel lands on one panel pixel. Set the recommended resolution and check your scaling settings.

It can show obvious problems, not an exact score. Visual tests reveal a clear tint, crushed shadows or oversaturated colors. A precise Delta E number needs a hardware colorimeter and calibration software.

Often because of a color range mismatch. If the computer sends limited range color (16-235) to a monitor expecting full range (0-255), blacks look grey and colors look flat. Set the graphics driver output to full RGB, or match the monitor HDMI black level setting.

Gamma controls how bright the mid-tones look between black and white. Most content is made for a gamma of about 2.2. Too high and the picture looks dark and contrasty, too low and it looks washed out.

4:4:4 means color is sent at full resolution for every pixel. TVs often reduce color resolution to 4:2:2 or 4:2:0, which is fine for video but makes colored text smeared when the TV is used as a monitor. Set the TV input to PC mode to get 4:4:4.

Usually a setting, port or cable is holding it back. Check the monitor's menu, then set the rate in Windows under Settings, System, Display, Advanced display. Use DisplayPort or a high-speed HDMI cable, because older HDMI 1.4 links run out of bandwidth at high resolutions and refresh rates. Update your graphics driver and set the rate in each game too.

Yes, it shows the rate your browser is really getting. It is the median of 120 real frame intervals, matched to the nearest standard rate. If a 144 Hz screen reads 60, the higher rate is not active. Keep the tab in front while it measures.

Ghosting is a trail, motion blur is softness. Ghosting leaves faint copies behind moving objects because pixels change color too slowly. Motion blur makes the whole object soft as your eye tracks it. Bright or dark halos instead of a trail mean overdrive is set too high.

Turn it on in both the monitor menu and the graphics driver, then run a VRR test. With variable refresh working, the moving pattern stays smooth without tearing as the frame rate changes.

Only partly. A browser test measures your reaction time plus the delay of your whole system. Measuring the display alone needs special hardware, so use our test to compare settings, such as game mode on and off.

PWM flicker happens when a screen dims its backlight by switching it on and off very quickly. Some people get eye strain or headaches from it at low brightness. Our test helps you spot it with your phone camera.

Squares that never respond. In the touch grid, slide your finger over every square. Any square that stays dark after several tries is a dead zone. If a whole strip fails, the digitizer or its cable is usually at fault.

Run four quick checks. Look for dead pixels on white and black, burn-in on grey, touch dead zones by drawing across the whole screen, and brightness at full. It takes about five minutes in the phone browser.

Open screentester.co in the TV browser. Check dead pixels, backlight bleed or clouding on dark grey, burn-in on OLED, and motion with the moving patterns. Do it inside the store return window.

Press each key and it lights up on the on-screen keyboard. Keys that do not light up are not registering. Press several keys together to check how many your keyboard can detect at once.

Click normally in the double-click test. It counts how many clicks register for each press. If single presses often count as two, the switch is wearing out.

Usually a permission or another app is the cause. Allow camera and microphone access when the browser asks, check your system privacy settings, and close other apps such as video call software that may be using the device.

Mark the fault, then copy or download the report. Turn on Mark mode, tap each faulty pixel to log its exact x and y position, and attach the report with a photo of the screen to your request. Test as soon as the screen arrives, while the return window is still open.

It depends on the retailer and where you live. Many stores allow 14 to 30 days, and in the EU and UK most online purchases come with at least a 14-day right to cancel. Test a new screen on the first day so you have time to act.

Some premium product lines and retailers promise zero bright pixels, but policies change often. Check the brand pixel policy for your exact model before buying, and keep your test report if you need to claim.

No. Every test pattern, reading and report is created inside your browser and stays on your device. Nothing is sent to a server unless you copy or download the report yourself.

No. The video and sound stay on your device and are never recorded or uploaded. You can withdraw permission at any time in your browser settings.

Not for everyone. The Stuck Pixel Fixer and some flicker tests flash rapidly and are not suitable for people with photosensitive epilepsy. They ask before starting and offer a gentle, no-flash option.

Yes. You can use the tools for personal or business purposes, including checking devices for customers in a shop or repair workshop. Please do not copy or resell the tools.

Use the contact form. Choose Bug report or Tool request, add the page link and your device, and we will reply, usually within 2 business days.