Reverse Text

Why anyone reverses text

The uses are more varied than they first appear. Puzzle setters and escape-room designers hide clues in reversed strings because they are trivially decodable once spotted but invisible at a glance. Developers use character reversal as a classic interview problem and as a quick way to check that a string-handling routine copes with Unicode. Writers reverse line order to flip a chronological list into reverse-chronological without retyping it, which is a genuine time-saver on a long changelog or timeline. And a certain amount of it is simply play — backwards usernames, mirrored captions, and the small pleasure of writing something that looks like nonsense until someone works out the trick.

The Unicode problem hiding underneath

Reversing a string sounds like the simplest operation imaginable, and it is a well-known trap. A naive reversal walks backwards through the underlying bytes, which works perfectly for plain English and breaks the moment anything else appears. An emoji is not one byte but several, and reversing them individually scrambles the sequence into a meaningless symbol. Accented characters are sometimes stored as a base letter followed by a separate combining accent mark — reverse those and the accent floats onto the wrong letter. Family emoji and flags are built from several joined code points and disintegrate entirely. This tool reverses by code point and keeps combining sequences together, which is why your emoji survive the trip.