First, 60 seconds of screen anatomy

Every pixel on your display is actually three sub-pixels — one red, one green, one blue. A white pixel is all three lit at full power; black is all three off; every other color is a mix. A “pixel defect” is almost always a sub-pixel defect, which is why the tell-tale is usually colored, not black-and-white.

Each sub-pixel has a tiny transistor that switches its liquid crystal or OLED emitter. Defects split into two families depending on what that transistor is doing:

• Stuck on — the sub-pixel is powered constantly. It can’t change, so it shows as a fixed bright or colored dot.
• Stuck off / dead — the sub-pixel gets no signal at all. It stays black on every background.

What each fault looks like

Defect	On black	On white	On a primary color
Stuck red sub-pixel	red dot	invisible	invisible on red; yellow on green, magenta on blue
Stuck green sub-pixel	green dot	invisible	invisible on green; yellow on red, cyan on blue
Stuck blue sub-pixel	blue dot	invisible	invisible on blue; magenta on red, cyan on green
Two stuck sub-pixels	cyan/magenta/yellow dot	invisible	invisible on its own mix; off-hue dot elsewhere
All three stuck on (“hot”)	white dot	invisible	white dot on every color
One dead sub-pixel	invisible	dim colored dot	dark dot on its own color
Dead pixel (all three off)	invisible	black dot	black dot on every color

The pattern to remember: stuck-on faults glow on dark screens; dead faults only show on lit screens. That’s why a serious check cycles both — black and white — not just the color your eye happened to catch the dot on. The tester walks through all five screens plus a custom hue in under a minute.

A two-minute diagnosis

1. Run the color test and stop on white. Any black dot = dead pixel or all sub-pixels off. Count them.
2. Switch to black. Any glowing dot = stuck-on sub-pixel(s); its color tells you which channel(s) are frozen.
3. Sweep red, green and blue. A dot that goes dark on exactly one primary is a dead sub-pixel of that color; a dot that keeps its own color against the others is a stuck one.

Why the difference matters

• Stuck pixels are sometimes fixable. A stuck-on sub-pixel is often a lazy liquid-crystal state rather than dead hardware — rapid color exercise (the exerciser on the home page) or gentle pressure can unstick it. Success is anecdotal but real enough to try before an RMA.
• Dead pixels are hardware-dead. A failed transistor doesn’t respond to flashing or massage. Your options are the retailer’s return window, the manufacturer’s pixel policy, or living with it.
• They’re graded differently by warranties. Most policies treat bright (stuck-on) defects as worse than dark ones — one bright dot may qualify where several dark ones wouldn’t.

When it’s not a pixel at all

Before you count defects, rule out impostors: dust and smudges (clean and re-check), a hair under a screen protector, and on OLED TVs, temporary image retention, which fades in minutes — unlike a defect, which is permanent and perfectly square-edged on the pixel grid.

Frequently asked questions

Is a stuck pixel the same as a hot pixel?

Almost — the terms overlap. A hot pixel usually means the whole pixel (all three sub-pixels) is stuck on, so it glows white on dark screens. A stuck pixel is the broader case: one or two sub-pixels frozen on, which produces a colored dot instead. Both are 'stuck on' faults; the fix odds are similar.

Can a dead pixel come back to life?

Practically never. A dead pixel means the transistor driving it has failed, and no software, flashing or pressure technique repairs dead hardware. Very occasionally a 'dead' dot turns out to be a connection fault that resolves itself, but plan around it being permanent: check your warranty options.

My dot is white on black screens but invisible on white — what is it?

A stuck-on pixel (all three sub-pixels frozen on). It shows white against black because it's emitting full power; on a white screen it blends in because white is all sub-pixels on. Run the exerciser on it — stuck-on pixels are the most recoverable kind.

The dot moves or disappears when I look straight at it — a pixel fault?

Probably not. Debris under a screen protector, dust on the panel surface, or a hair can masquerade as a pixel defect. Real defects sit exactly on the pixel grid and look identical from every angle. Clean the screen and re-check before assuming hardware failure.

Are stuck pixels covered by warranty?

Depends on the brand and how many you have. Bright-dot-friendly policies (Dell's Premium Panel Exchange, ASUS's ZBD on covered models) swap for even one; others require clusters of defects under ISO-derived rules. The brand policies guide maps it out — and a retailer return beats all of them.