Reversed text or mirror writing?
Reversed text keeps normal letters and only flips their order, so Hello becomes olleH. It is handy for word games, puzzle clues, checking palindromes like "racecar" and messages that friends have to decode.
Mirror writing goes further and flips every letter left to right as well, so the whole line looks like its own reflection: hold the screen up to a mirror and ollɘH reads as Hello again. Upside-down text, also included here, turns the letters 180 degrees instead.
Where mirror letters come from
Unicode has no mirror switch, so the generator uses look-alike characters. Я and И are Cyrillic letters (Ya and I in Russian) that happen to look like a reversed R and N, ɘ is the reversed e of the phonetic alphabet, and ꟻ and ꟼ are reversed F and P that Unicode includes for transcribing old Latin inscriptions.
Symmetrical letters such as A, H, M, O, T and X stay as they are, b and d trade places, and brackets turn around. The question mark becomes ⸮, a reversed question mark once proposed for marking rhetorical questions. Find more marks like it in punctuation symbols.
Mirror writing in real life
Leonardo da Vinci filled his notebooks with mirror writing, and many ambulances show the word AMBULANCE reversed on the front so drivers can read it in their rear-view mirror. Online, backwards text is mostly for fun: secret-looking captions, riddles and usernames that make people look twice.
It is not a real code, since anyone can reverse it again here. Screen readers may read mirror letters as Cyrillic or phonetic characters, and search may not match them, so keep the important part of a message readable. To flip text vertically, use the upside down text generator, or explore every style in the fancy text generator.