Spot the difference

Spot the difference is a type of puzzle game in which players compare two otherwise identical pictures and try to identify a set number of subtle alterations between them. The images are typically illustrations or photographs that have been deliberately altered through photo manipulation, with differences ranging from color changes to missing or added objects. The puzzle format is common in children's activity books, newspaper puzzle pages, and digital and mobile games, and usually presents a fixed count of differences with an answer key provided separately. Solvers rely mainly on careful visual comparison, though some approach the puzzle by deliberately crossing their eyes to fuse the two images the way autostereogram viewers do, which can make a difference appear to flicker in and out of view, or by digitally overlaying the two images and inverting one to highlight mismatched pixels. Because it tests observation and pattern recognition rather than strategy or knowledge, spot the difference is widely used as a light, accessible puzzle format for all ages.