Backlight is the layer of illumination positioned behind an LCD display panel. Because LCD pixels do not emit their own light, the backlight is what makes the image visible. Modern backlight technologies — edge-LED, direct-LED, mini-LED — directly determine brightness, uniformity, contrast and energy efficiency of a display.

In digital signage, choosing the right backlight technology has significant implications: higher brightness (measured in nits) enables outdoor or sun-exposed installations; better local dimming improves contrast in dark environments; mini-LED narrows the gap between LCD and OLED in image quality.