Click to enter fullscreen
Isolate red, green, and blue output
RGB channel test
Isolate each RGB subpixel channel with pure primaries, secondaries, single-channel ramps, and repeating RGB bars. Spot stuck subpixels, missing channels, and cable faults faster than mixed white or grey fills.
Channel pattern
Ramp & bars
Direction
What to look for
Clean channel
Pure primary looks solid with no foreign dots. Ramps stay smooth for that channel.
Stuck or missing
Bright dots of another hue, a black primary, or early banding on one ramp — note the channel and check cable/GPU before RMA.
Run & cycle
- ← → Cycle patterns
- F Fullscreen
Free RGB channel test — isolate red, green & blue
A browser RGB channel test with pure primaries, cyan/magenta/yellow secondaries, white, per-channel ramps (2–256 steps), adjustable RGB bars, and RGB thirds. Built for stuck-subpixel checks, weak-channel diagnosis, and cable/GPU faults — not a spectrophotometer, ICC profiler, or factory pixel-fixer tool.
Pure channel fills
Per-channel ramps & bars
Fullscreen cycle workflow
What an RGB channel test shows
LCD and OLED pixels are built from red, green, and blue subpixels. Isolating one channel reveals defects that mixed greys and UI chrome hide — and separates panel faults from signal-path failures.
Subpixels vs whole pixels
Primaries vs secondaries
Panel vs cable vs GPU
How to run an RGB channel test online
About two minutes: raise brightness, start on pure red, fullscreen, then walk every primary and ramp until you know which channel — if any — is failing.
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Prep the panel
Wipe dust so smudges are not mistaken for stuck dots. Raise brightness near 100% for bright stuck-subpixel checks. Dim strong ambient light so reflections do not mask thin defects. See also: dead pixel test .
Tip Mark suspicious spots mentally, then confirm on a second primary
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Isolate each channel
Start on Pure red, enter fullscreen, and scan slowly. Then advance to green, blue, secondaries, white, and the three channel ramps. Use RGB bars if you suspect vertical stripe or subpixel-layout issues. See also: how to read results .
Tip Hold 3–5 seconds per pattern — rushing hides edge defects
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Separate cable from panel
If one primary is nearly black, reseat or swap the cable and GPU port, then retest. Persistent colored dots at the same coordinates after a cable change point to the panel — document brightness and pattern for warranty notes. See also: uniformity / bleed check .
Tip Photograph the defect on the pattern where contrast is highest
How to read RGB channel results
Clean primary
Stuck or hot subpixel
Missing channel / black primary
Early banding on one ramp
When to run an RGB channel check
Use this RGB channel test when you need subpixel-level clarity — unboxing QA, a “tint” complaint, a suspected bad cable, or comparing two monitors side by side.
New monitor unboxing
- Cycle pure R, G, B plus white in fullscreen.
- Note any fixed colored dots before the return window closes.
- Pair with a dead-pixel sweep if you find candidates.
Recommended Photograph defects on the primary where they contrast most — that evidence travels better than a vague “bad screen” claim.
Tinted or “missing color” desktop
- If one primary is near-black, swap cable and port first.
- Confirm GPU color depth is not stuck at 6 bpc.
- Only then treat it as a panel or scaler fault.
Recommended A cable that drops red is far more common than a panel that forgot how to make red.
Gaming / high-Hz panel QA
- Run channel ramps at 64 and 256 steps.
- Check RGB bars for vertical stripe oddities.
- Retest at native Hz after a refresh-rate check.
Recommended Channel banding that only appears under heavy GPU load may be bandwidth or link training — not permanent subpixel damage.
Laptop vs external display
- Run the same pattern sequence on both screens.
- Note which device fails which primary.
- Use the laptop’s built-in panel as a known-good reference when possible.
Recommended If only the external fails, focus on dock, dongle, and cable before assuming the portable panel is perfect.
Reliable RGB channel setup
Fullscreen & focus
Brightness & ambient light
One pattern at a time
Confirm before RMA
RGB channel test FAQs
How is an RGB channel test different from a dead pixel test?
A dead pixel test cycles mixed fills (often including black and white) to find dead or stuck pixels. An RGB channel test isolates single-channel output and per-channel ramps so subpixel-level faults and missing channels stand out on each primary.
Which patterns should I run first?
Start with pure red, green, and blue in fullscreen, then white and the three channel ramps. Add RGB bars or thirds if you suspect vertical stripe or layout issues. Secondaries help when one channel looks weak but not fully dead.
What does a green dot on a pure red screen mean?
Usually a stuck green subpixel — it stays lit while the red field should dominate. Confirm on pure blue and black; if the same coordinates glow green, document it for warranty rather than assuming dust.
Why does pure red look almost black?
Often a cable, adapter, or GPU output fault dropping the red channel — not always a broken panel. Reseat HDMI/DP, try another port, then retest. If red returns, the panel was fine.
Can this fix stuck pixels?
No. This page diagnoses channel output. Pixel-fixer apps flash colors for long periods hoping to unstick a subpixel; success is uneven and this tool does not claim repairs.
Is this a colorimeter or calibration tool?
No. An RGB channel test is a visual isolation check. Accurate white point, gamma, and gamut need a colorimeter plus profiling software — use our color calibration patterns after channels look intact.
Do I need to install software?
No. This is a free RGB channel test online in the browser. Results still depend on fullscreen use, brightness, and a clean screen surface.
How many ramp steps should I use?
64 steps is a good starting point for spotting early banding. Push toward 128–256 steps when comparing two panels or checking whether one channel posterizes sooner than the others.
