OLED burn-in, without the panic
OLED burn-in is uneven aging: each pixel is an organic emitter that dims very slowly with use, so content that parks the same bright elements in the same places for thousands of hours wears those regions faster, leaving a ghost. It is cumulative and permanent, unlike image retention, which fades on its own.
OLED earns its picture quality by giving every pixel its own light: an organic emitter that switches fully off for black and lights only when asked. The same property is the root of its one famous weakness. Emitters age with use, very slowly, and they age exactly as much as they are used. Burn-in is nothing more mysterious than that ledger, made visible.
What burn-in actually is
Every hour an OLED pixel spends lit, it dims by an imperceptible amount, and the blue emitters age fastest of the three. If viewing is varied, the wear spreads evenly and the whole panel drifts together, invisibly, over many years. If the same bright element sits in the same place for a large fraction of the panel's life, a channel logo, a news ticker, a game's health bar, a taskbar, those pixels bank more hours than their neighbors. Eventually the difference shows as a ghost of the element, faintest in flat mid-tones like a gray field or a clear sky.
That is why burn-in is a statistics problem, not an accident. No single image causes it at any sane brightness; it is thousands of hours of the same image winning the same pixels.
Retention is not burn-in
Panels also show a short-lived cousin: image retention, a faint ghost of something recently displayed that fades within minutes once the content varies. Retention is chemistry relaxing, not wear accumulating, and it is not a warning sign of imminent burn-in. The test is time: a ghost that survives an evening of normal varied viewing has graduated from retention to something worth attention.
If you want to check a panel deliberately, a flat gray field is where uneven wear shows soonest, with a mid-gray revealing more than white or black.
The habits that matter
Vary the diet. The panel does not care what it shows, only how unevenly. Mixed content is the whole defense, and a display used for movies, games and browsing in rotation is at essentially no practical risk.
Manage the static passengers. Auto-hide the taskbar and dock on a desktop OLED, let the screen sleep rather than hold a paused frame for hours, and prefer dark or shifting screensavers to none. Game HUDs and channel tickers are the classic offenders; brightness is their multiplier, so high-brightness static elements are the specific combination to avoid making a lifestyle.
Let the television do its maintenance. Modern OLED TVs run brief pixel-compensation cycles after use and a longer one at wide intervals, automatically, provided they go to standby instead of losing power at a wall switch.
And for what it is worth on this site: a fullscreen solid color is even wear by definition, and a black screen on an OLED is the panel at rest, every pixel off, drawing close to nothing. The tool you are reading about is one of the safer things an OLED can display.