Burn-in, or screen burn, is the permanent darkening of a CRT display as a result of a static image displayed for a prolonged time. The phosphors in a CRT are excited by an electron beam, and there in turn emit light. This light results in some heat, and if the phosphor is illuminated for too long, the phosphor actually burns. Thereafter, the image that was displayed will appear as a darkend impression within any other image on the screen. The time required to burn-in an image depends upon the quality of the phosphors among other factors. Use of screensavers, as the name implies, helps to prevent burn-in with computer displays. By using some moving image, the screensaver ensures that no pixel is displayed for an extended time in a static manner. Before the institution of the SMPTE color bars, the RCA Indian Head was the most commonly burned-in image due to a viewer leaving a television on overnight during which the time a station displayed no programming was filled with the test card.

Burn-in was initially a problem associated with plasma flat panel televisions as well. However, manufacturers have worked largely successfully to improve the quality of plasma technology's resistance to burn-in over the past several years, to the point where it is far less of a major concern with plasma panels.