Display Testing Tools

Screen and monitor diagnostics you can run directly in your browser. Test for dead pixels, check your true refresh rate, and clear image retention safely.

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Dead Pixel Test

Identify stuck or dead pixels with full-screen color cycles.

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Burn-in Fixer

Reduce OLED/LCD image retention using rapid pattern cycling.

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Refresh Rate Test

Verify your monitor's actual refresh rate in Hz.

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Screen Ruler

Measure elements on your screen in pixels, cm, and inches.

Online Monitor & Screen Diagnostics

Most Popular Display Checks

Whether you just bought a new monitor or are experiencing visual glitches on an old screen, select the diagnostic test that fits your issue:

  • Test for Dead Pixels: Use this immediately after buying a new screen to spot manufacturing defects, black dots, or bright stuck pixels.
  • Check Monitor Refresh Rate: Use this to verify that your gaming monitor is actually outputting 144Hz, 240Hz, or 360Hz instead of defaulting to 60Hz.
  • Reduce Image Retention (Burn-in Fixer): Run this rapid color cycler if your OLED or IPS panel is displaying faint ghost images of old browser windows.
  • Measure On-Screen UI: Use this digital ruler and physical calibration feature to measure elements in exact pixels, centimeters, or inches.

Which display test should you run first?

If you are not sure which tool matches the issue, use this quick routing guide:

  • New monitor inspection or warranty check: Start with the Dead Pixel Test.
  • Monitor feels less smooth than expected: Start with the Refresh Rate Test.
  • Faint shadows of old UI or app bars remain on screen: Start with the Burn-in Fixer.
  • Need exact on-screen dimensions for UI or design work: Start with the Screen Ruler.

How to check a new monitor for dead pixels

When unboxing a new laptop or desktop monitor, finding a dead pixel early is crucial for warranty returns. Our Dead Pixel Test fills your screen with pure, high-contrast colors (Red, Green, Blue, Black, White). By cycling through these colors in a dark room, you can easily spot if a microscopic transistor has failed (appearing as a permanent black dot) or if it is "stuck" (glowing brightly on a single color).

Dead pixel vs stuck pixel (important difference)

Many users search for a "dead pixel fix" when the panel actually has a stuck pixel. A dead pixel is typically a permanently black pixel caused by transistor failure, and software usually cannot repair it. A stuck pixel is a pixel locked on one color channel (red, green, or blue), and rapid color cycling can sometimes restore normal behavior. This is why running the Dead Pixel Test first, then trying the Burn-in Fixer or pixel stimulation pattern, is a practical troubleshooting flow.

How to verify your true monitor refresh rate

A very common mistake among PC gamers is buying an expensive high-refresh-rate monitor, plugging it in, and playing at 60Hz for years without realizing it. Windows and macOS often default new displays to 60Hz for compatibility reasons. By running our Refresh Rate Test, your browser measures frame timing to estimate your active refresh rate. If the test says 60Hz on a 144Hz monitor, you need to adjust your OS display settings and ensure you are using a DisplayPort or high-speed HDMI cable.

Why a 144Hz or 240Hz monitor may still run at 60Hz

High refresh monitors often underperform because of configuration issues, not panel defects. Common causes include:

  • OS display settings still on 60Hz: Windows or macOS may not switch automatically after connecting a new monitor.
  • Wrong cable or port: Some HDMI cables or older ports cannot carry the bandwidth required for high refresh modes at your chosen resolution.
  • Resolution-refresh tradeoff: Your GPU or monitor may support 144Hz only at specific resolutions or color settings.
  • Docks and adapters: USB-C docks, KVMs, or adapters can force lower refresh modes.
  • In-game settings mismatch: Some games run in a different display mode than your desktop and may lock to 60FPS/VSync.

OLED image retention vs permanent burn-in

These two problems are often confused, but they are not the same. Image retention is usually temporary and may appear after static UI elements (taskbars, HUDs, tickers) remain on screen for a long period. It can fade over time and may improve with content cycling. Permanent burn-in is physical wear of the panel subpixels and cannot be reversed by software. Use the Burn-in Fixer as a temporary recovery attempt for retention, not as a guaranteed repair for permanent OLED degradation.

How to reduce temporary image retention safely

If your screen shows faint ghost images, first lower brightness and display varied full-screen content for a while. Then run the Burn-in Fixer for a short session and re-check the panel using plain gray, white, and color backgrounds. If the ghost image remains unchanged after repeated rest periods and normal content use, the issue may be permanent burn-in rather than temporary retention.

How to calibrate a screen ruler on phones, Macs, and high-DPI displays

Digital rulers can be pixel-perfect in software while still being physically wrong on the screen if device scaling is active. Phones, tablets, and Retina-class displays compress multiple hardware pixels into one CSS pixel. For accurate centimeters or inches, use the Screen Ruler calibration step with a real reference object such as a bank card or a known-length ruler. After calibration, measurements are much more reliable for UI layout checks and quick physical comparisons.

Device Specific Display Behaviors

Screens behave differently depending on their panel technology and operating system scaling. Keep these details in mind:

  • OLED TVs & Smartphones: OLED panels offer perfect blacks but are susceptible to "image retention". If you leave a static app open for hours, a faint shadow may remain. While permanent burn-in cannot be fixed, temporary retention can often be cleared using our Burn-in Fixer.
  • Gaming Monitors (Asus, BenQ, LG): Fast VA and TN panels sometimes experience "pixel overshoot" or smearing. Use our color tests to observe how your panel handles rapid color transitions.
  • Apple MacBooks (Retina Displays): macOS utilizes a pixel scaling method that groups multiple physical hardware pixels into a single "software" pixel to make text sharper. Because of this, default web measurements are inaccurate on Macs. You must use the physical card calibration tool inside our Screen Ruler to get true real-world dimensions.

New monitor quick checklist before return window closes

  1. Panel defect check: Run the Dead Pixel Test in a dim room across all color screens.
  2. Refresh verification: Run the Refresh Rate Test after setting your target Hz in the OS.
  3. Retention check: Inspect gray and solid-color backgrounds for shadows, then try the Burn-in Fixer if needed.
  4. Measurement check: Use the Screen Ruler if you need to verify UI scaling or on-screen physical dimensions.

Privacy and Browser Safety

Unlike desktop diagnostic software, browser-based display tools reduce installation friction and security risks. These checks do not require camera access, microphone permissions, or administrative rights. The rendering happens locally using standard HTML5 Canvas and CSS features. (Note: The Burn-in Fixer features rapidly flashing lights and should not be used by individuals with photosensitive epilepsy.)

Explore more: Is your screen working perfectly but your gaming inputs feel laggy? Go to the TestMyTech homepage to explore our Mouse and Gamepad input diagnostics.

Display Diagnostics FAQ

Can a website fix a dead pixel?

No software can fix a truly "dead" (black) pixel, as the transistor is permanently broken. However, software can often fix a "stuck" pixel (a pixel stuck on red, green, or blue) by rapidly cycling colors to force the liquid crystal to reset.

Why does my 144Hz monitor only test at 60Hz?

By default, Windows and macOS often set new monitors to 60Hz. You must manually change the refresh rate in your operating system's display settings. Additionally, ensure you are using a DisplayPort or high-speed HDMI cable capable of 144Hz bandwidth.

Does the burn-in fixer work on OLED screens?

It can help clear temporary "image retention" (ghosting) caused by static UI elements on OLED and LCD panels. However, permanent OLED burn-in represents physical degradation of the organic pixels and cannot be reversed by software.

Do I need to install anything to test my screen?

No. All of our display diagnostic tools run locally within your web browser using HTML5 and JavaScript rendering. No downloads, browser extensions, or administrative privileges are required.

Why is the screen ruler inaccurate on my phone or Mac?

Modern high-resolution displays (like Apple Retina or smartphone screens) use pixel scaling, which packs multiple hardware pixels into one software pixel. You must use the ruler's physical "Calibration" feature to get accurate real-world measurements in centimeters or inches.