ROT13 Encoder & Decoder

ROT13 is a simple letter-substitution cipher that rotates each letter 13 places through the alphabet — A becomes N, B becomes O, and so on. Because 13 is exactly half of the 26 letters, applying ROT13 a second time brings every letter back to where it started, which means the same operation both encodes and decodes. This tool gives you ROT13 plus three close relatives, with a live two-way preview and one-click copy for every variant.

How it works

Pick a variant from the dropdown and start typing. The output updates on every keystroke, so there is no encode or decode button to press — for the self-inverse variants you simply paste scrambled text in to read it, or plain text in to scramble it.

• ROT13 (letters) — the classic. Shifts the 26 letters by 13 and leaves digits, spaces and punctuation untouched. This is the encoding used to hide Usenet spoilers and puzzle answers.
• ROT13 + ROT5 (letters and digits) — adds ROT5 on the digits 0 to 9, so numbers in your text get scrambled too. Five is half of ten, so this stays self-inverse.
• ROT47 (all visible ASCII) — rotates every visible ASCII character (from exclamation mark through tilde) by 47 places, so letters, numbers and symbols all change while spaces stay as spaces. It looks much more scrambled than ROT13 but is still its own inverse.
• ROT-N (custom shift) — a general Caesar cipher where you choose any shift from 1 to 25. Only shift 13 is self-inverse; for any other value the tool tells you the matching decode shift, which is 26 minus your number.

A Decode check box re-applies the transform to the output so you can confirm a clean round-trip, and the All variants panel shows every encoding of your current text at once with its own copy button. Everything runs locally in your browser — no text is ever uploaded, logged or stored.

Example

Type the sentence Attack at dawn with the ROT13 variant and you get Nggnpx ng qnja. Paste that result straight back in and you read Attack at dawn again, because ROT13 is its own inverse. Switch to ROT47 and the same sentence becomes a string of letters and symbols, while ROT13 + ROT5 would also shuffle any digits such as a year or a phone number.

ROT ciphers are great for hiding spoilers or quiz answers in plain sight, but remember they are obfuscation rather than real encryption — anyone can reverse a fixed public shift, so never rely on them to protect anything sensitive.