Is image retention the same as burn-in?

No. Retention is temporary and fades once the screen shows other content. Burn-in is permanent uneven wear of the pixels, most common on OLED. A ghost that is still there after a day of normal use is more likely burn-in.

Burn-In Test

Burn-in and image retention show up as faint ghosts of things that were on screen for a long time, such as a taskbar or a game HUD. Flat fields make those ghosts easiest to see.

Retention is most visible on mid-gray. Look for ghost outlines of taskbars, docks, logos or keyboards.

Runs entirely in your browser. Nothing is uploaded or stored.

How to use

Press Start test and begin with the gray field. Retention is most visible on mid-gray.
Look for outlines of static interface elements: a taskbar, dock, logo, status bar or keyboard.
Step through white, black and the primary colors. Burn-in on OLED often shows more on one color than another.
If you see a ghost, note the time, use the screen normally or leave it off, and check again later. Retention fades; burn-in does not.

What this test can detect

Image retention: a temporary ghost image that fades over minutes or hours.
Possible burn-in: a ghost image that stays the same day after day.
Uneven wear on OLED panels, such as a dimmer band where a taskbar sits.

Important

Software cannot tell retention from permanent burn-in. Only time and repeated checks can, and a manufacturer or repair shop is the final word.
Clouding, mura and backlight bleed can look like ghosts. Compare with the uniformity and backlight tests before drawing a conclusion.
This page cannot repair burn-in. Pixel refresh routines built into some TVs and phones may reduce retention, but they are not run from a browser.

Questions

Is image retention the same as burn-in?: No. Retention is temporary and fades once the screen shows other content. Burn-in is permanent uneven wear of the pixels, most common on OLED. A ghost that is still there after a day of normal use is more likely burn-in.