Mirror text is writing flipped left to right, so it looks the way normal text looks in a mirror and reads correctly when you hold it up to one. "Hello world" becomes blɿow ollɘH: the order is reversed, and letters are swapped for mirrored forms such as ɘ for e and ɿ for r.

Unicode has no switch that mirrors a letter, so a mirror text generator builds each mirrored letter from real characters: some are officially reversed letters like Ǝ, others are look-alikes from alphabets such as Cyrillic, where Я resembles a mirrored R. The result copies and pastes like any other text. Everything runs in your browser.

Leonardo da Vinci is the best-known mirror writer. He wrote most of his personal notes from right to left and switched to normal writing when others were meant to read them. His reason is unknown. One suggestion is that, as a left-hander, writing right to left kept his hand from smudging wet ink.

Fluent mirror writing is rare. An informal experiment by an Australian newspaper, reported by ABC Science in 2004, found 10 true mirror-writers among 65,000 readers. A 2004 paper in Archives of Neurology found that left-handed people tend to be better at it, perhaps because writing right to left comes more naturally to them. Many children also mirror-write some letters while learning to write.

Unicode mirrors only a small set of characters by itself. Brackets such as ( and [ carry the Bidi_Mirrored property, so inside Arabic or Hebrew text an opening bracket is drawn facing the other way. Letters never change shape, which is why mirror text swaps in separate characters instead.

The right-to-left override, U+202E, makes text display in reverse order without changing the letters. It is not used here: many apps strip it, it reverses everything typed after it, and it has been used to disguise file names and, in the 2021 Trojan Source research, to make code look different from what it does.

Font support decides what you see. Latin, Greek, and Cyrillic letters such as Ǝ, ɘ, ϱ, and Я display almost everywhere. The look-alikes for B, D, F, G, J, K, P, j come from Canadian Syllabics, Lisu, and Georgian, and the reversed question mark ⸮ is rarer still, so Safest fonts leaves those characters plain.