Full Blue Screen

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Fill your whole screen with pure blue to test the blue sub-pixel channel and reveal dead pixels on a colored field. Free and runs in your browser.

Tap to open full screen

Pick a color

Press Esc to exit, or use the ← → arrow keys to switch colors while in full screen.

What is it for?

Find dead pixels
A solid field makes pixels that never light up easy to see — check each color in turn.
Find stuck pixels
On a black screen, sub-pixels stuck on bright stand out instantly.
Clean your screen
A bright, even white surface reveals dust, smudges and fingerprints as you wipe.
Lightbox & tracing
Turn your display into a backlight for tracing drawings or viewing slides.
Bias & fill light
Use a full color screen as ambient bias lighting or a soft fill light for calls.
Chroma-key backdrop
A pure green or blue screen works as a quick background for green-screen effects.

About Full Blue Screen

The Full Blue Screen tool covers your display in pure blue (#0000FF), activating only the blue sub-pixel of every pixel. It completes the trio of primary-color tests: any defect that appears on the blue field but not on red or green points squarely at a failed blue sub-pixel.

Blue faults are the easiest to miss in daily use because blue contributes the least to perceived brightness — a weak blue channel quietly skews whites toward yellow long before you spot a bad pixel. A solid blue field also makes panel uniformity issues visible, from corner tinting to faint vertical banding.

Blue screens have a production use too: blue is the traditional alternative chroma-key backdrop, historically preferred by filmmakers when the subject wears green or for cleaner edges with certain cameras. The page is free, fully browser-based, supports arrow-key color switching and a custom picker, and exits with Esc.

How to use Full Blue Screen

  1. Click the monitor preview or "Go full screen" to fill the display with pure blue.
  2. Scan the panel for dark dots and off-color specks against the blue field.
  3. Compare edges and corners against the center for tint and uniformity issues.
  4. Switch to red or green with the ← → arrow keys to cross-check any suspect pixel, then press Esc to exit.

Frequently asked questions

It isolates the blue channel: dark dots mean the blue sub-pixel at that spot is dead, while colored specks mean another channel is stuck on. It also exposes uniformity problems — tinted corners or banding — that a busy desktop hides.

Blue is the classic choice when the subject wears green, has green props, or when green spill on skin and hair is a problem. Green keys more easily under weak lighting on digital cameras, but blue often gives cleaner edges around fine detail.

No — it just fills your display with a solid blue color for testing. Nothing about your system is affected, and pressing Esc returns you to the normal page instantly.

Yes — free, no sign-up, and entirely client-side. The page paints your screen blue locally in the browser and sends nothing anywhere.

Blue accounts for the smallest share of perceived brightness, so a dead blue sub-pixel barely dims a white image — it mostly shifts that pixel slightly toward yellow. On a pure blue field, though, the same fault appears as an obvious dark dot.
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