The phrase glow up became common online slang for a dramatic improvement in appearance or style, and glow down was adopted as its comic opposite for a deliberate step backwards. Short clips using both phrases together spread through meme edits and transformation videos, where creators pair the contrast with before and after footage. The format stays popular because it works in both directions, celebrating a real improvement or undercutting it for humour, and it needs no context beyond the two shots it compares.