How to Use a Dead Pixel Test (Step-by-Step)

To use a dead pixel test correctly: clean the screen, set brightness to 100%, enter fullscreen mode, then cycle through five solid colors (red, green, blue, white, black) scanning each one slowly for anomalies. The test takes about 60 seconds and catches every dead, stuck, or hot pixel on a typical screen. The order of steps matters — running the test out of order, at low brightness, or windowed misses defects you would later regret. This walkthrough covers the eight steps in detail.

Before you start: what you need

• A screen to test (phone, tablet, monitor, laptop, TV with browser).
• A clean microfiber cloth.
• Roughly 60 seconds for the basic test, plus 10–30 minutes if you find a stuck pixel and want to try the fixer.
• The Screen Ruler dead pixel test — or any equivalent online tool that supports fullscreen mode.

You do not need: any installed app, any account, any payment. Browser-based dead pixel tests work on every platform.

Step 1: clean the screen

Wipe the entire screen with a microfiber cloth before starting. This single step prevents the most common false alarm.

Smudges, dust, and skin oil look identical to dead pixels — small dark dots on a bright background. Many users see what appears to be a stuck pixel, panic, and discover after the test that it was a fingerprint. Cleaning takes 10 seconds and saves you from the cycle of "is this real, let me re-test, oh wait."

If you have a screen protector with embedded dust or scratches under it, the test will not distinguish those defects from genuine pixel failures. Consider removing the protector, testing the bare screen, then re-applying.

Step 2: set brightness to 100%

Maximize the screen brightness in Settings or with the brightness keys. Defects are far easier to see at full brightness:

• Dead pixels show as obvious black dots against bright backgrounds when the rest of the screen is at 100%.
• Stuck pixels stand out more vividly against a dim black background when the screen is at maximum brightness.
• Some OLED panels use pulse-width modulation (PWM) at low brightness, which causes rapid flicker that masks subtle defects.

If you are testing a screen on a laptop, switch to AC power first — most laptops dim automatically on battery to conserve power, even when set to 100%.

Step 3: enter fullscreen mode

Press F11 in most browsers (Cmd+Ctrl+F on Mac), or use the test tool's built-in fullscreen toggle. The Screen Ruler dead pixel test has a button for this.

Why fullscreen matters:

• Browser chrome covers the top edge. The URL bar, tab strip, and bookmarks bar block the top 60–100 pixels of the visible area, where edge defects often live.
• Notifications cover other regions. macOS notifications, Windows system tray popups, mobile status bars all hide pixels.
• Visual context distracts. A solid color edge-to-edge is much easier to scan than a colored area surrounded by other UI.

If your phone has a notch or punch-hole camera, parts of the screen near it may not be testable in fullscreen. Note this and skip those areas — they are unlikely to have failures regardless.

Step 4: start with red

Most dead pixel tests open on a red field by default. Scan the entire screen slowly, top-left to bottom-right, looking for any pixel that is not red.

What to look for:

• Black dots — dead pixels (no light).
• White dots — hot pixels (full brightness).
• Green or blue dots — stuck pixels with the red subpixel dead.
• Cyan, yellow, or magenta dots — partial subpixel failures.

A pristine screen has none of these. Even one dot is worth investigating.

Speed matters less than coverage. Scan systematically — top edge first, then left to right in horizontal bands, working downward. The whole scan takes 10–15 seconds per color.

Step 5: move through green, blue, white, black

Cycle through each color in this order. Do not skip any — different colors reveal different defects:

• Green — green is the brightest of the three primary subpixels, so dead pixels are most obvious here.
• Blue — blue subpixels are slightly dimmer; some stuck-blue defects only show up against a non-blue field, but stuck-non-blue defects show up here.
• White — all three subpixels at maximum. The classic test for dead pixels (truly black dots on bright white).
• Black — all subpixels off. The classic test for stuck pixels and hot pixels (bright dots on a dark field).

Spend 10–15 seconds on each color. The full cycle takes about a minute.

Step 6: mark suspicious areas

When you spot a suspect dot, note its rough position before moving to the next color. A dot at "top-right corner, about 1 cm in from the edge" should appear in roughly the same spot on the next color, confirming it is a real defect rather than a transient visual artifact.

The Screen Ruler dead pixel test supports clicking the screen to drop a marker at the suspected location, which persists across colors. Use this if your test tool supports it.

A defect that appears on red but not on green or blue is most likely a smudge in your eyes (after-image from the previous color). Wait 5 seconds and look again. Real defects are persistent across colors.

Step 7: re-clean and re-test if you found anything

If you found one or more suspicious dots:

1. Re-wipe the screen with a clean part of the microfiber cloth.
2. Re-run the cycle.
3. If the dots persist in the same locations, they are real defects.
4. If they disappear, they were dust or smudges.

The most stubborn smudges hide in a thin film of skin oil that does not respond to a single wipe. If a dot reappears even after cleaning, try a screen-cleaning solution (or distilled water, sparingly) on the cloth.

Step 8: run the fixer if you found a stuck pixel

A stuck pixel — one that is permanently on at one color — is sometimes recoverable. The Screen Ruler dead pixel test includes a fixer mode that cycles a small region around your marked location through rapid color changes.

To run the fixer:

1. Mark the stuck pixel's location during the test.
2. Switch to fixer mode (the test tool will have a button).
3. Position the cycling region over the stuck pixel.
4. Run for at least 10 minutes; up to 30 minutes for stubborn cases.
5. Re-test on the standard 5-color cycle to see if it cleared.

The fixer works by rapidly toggling each subpixel state, exercising the cell or LED in the hope of unjamming it. Success rates depend on:

• How long it has been stuck. Recently-stuck pixels (caught within days) have higher success rates than ones that have been stuck for years.
• Panel type. LCDs respond better to fixers than OLEDs because the underlying mechanism (a stuck liquid-crystal valve) is more reversible than a damaged OLED diode.
• Whether it is genuinely stuck or actually dead. A truly dead pixel (always black) will not respond to any fixer. Only stuck pixels (always on at a color) have any chance.

If 30 minutes of fixer does not help, accept that the pixel is permanent. Document its location for warranty claims.

What to do if you find dead pixels

The next step depends on the situation:

• Within warranty (new device): contact the manufacturer or retailer. Apple typically replaces iPhones and iPads with any dead pixel under warranty. Samsung's threshold is 3+ bright dots or 5+ dark dots within 90 days. Document with photos and the test date before contacting support.
• Used or refurbished purchase: if you find dead pixels on a recently-purchased used device, you may have grounds for return depending on the marketplace policy.
• Out of warranty: a screen replacement is the only fix. Cost varies from ~$80 for some Android phones to $400+ for iPhone Pro models. Often not worth it unless the defect is large or in a critical area.
• A single isolated dead pixel on an older device: usually not worth fixing. Most users adapt within a week and stop noticing.

Common mistakes

• Testing in a bright room. Sunlight or strong overhead lighting reflects off the screen and washes out dim defects. Test in a moderately lit room or with the screen tilted away from light sources.
• Skipping a color. Each color reveals different defects; running just red or just white misses subpixel-specific failures.
• Not entering fullscreen. Browser chrome covers ~5% of the screen, often where edge defects live.
• Trusting the first scan. Re-test if you find anything; smudges are far more common than real defects.
• Running the fixer on a dead pixel. Fixer mode cannot revive a truly dead pixel. Save the time for stuck pixels.

Summary

Eight steps for a reliable dead pixel test: clean, max brightness, fullscreen, red → green → blue → white → black, mark suspect dots, re-clean and re-test, run fixer for any stuck pixels. Total time: ~60 seconds plus an optional 10–30 minutes for fixer mode. The Screen Ruler dead pixel test automates the color cycling and includes a fixer mode out of the box.

For background on what the different defect types are, see the pillar guide on dead pixel test. For ten advanced techniques and edge cases, see tips and tricks.

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This article supports the Screen Ruler dead-pixel-test tool.