ROT13 Encoder / Decoder

ROT13 replaces each letter with the one 13 places further along the alphabet: A becomes N, B becomes O, and so on, wrapping around at Z. It has been used since the early days of Usenet to hide text from a casual glance — a spoiler, the answer to a riddle, a punchline — while letting anyone who wants to read it do so in one click. This tool encodes and decodes ROT13 and three related variants.

Why one step does both

The Latin alphabet has 26 letters, and 13 is exactly half. Shifting by 13 twice is a shift of 26, which brings every letter back to itself. So the same operation hides and reveals: paste ROT13 text to read it, or plain text to hide it. Capitals stay capitals, and spaces, digits and punctuation are untouched, which is why ROT13 text still looks like sentences: “Uryyb, jbeyq!” is “Hello, world!”.

ROT47

ROT47 works the same way on all 94 printable ASCII characters, from ! to ~, rotating by 47, half of 94. Digits and punctuation are scrambled too, so “Hello 2026” becomes “w6==@ a_ae”. It hides numbers and symbols that ROT13 would leave visible, such as in email addresses or code, and is also its own inverse.

ROT5 and ROT18

ROT5 rotates only the digits 0–9 by five: 0 and 5 swap, 1 and 6, and so on. ROT18 combines ROT13 for letters with ROT5 for digits, hiding both while keeping punctuation readable.

Where you will meet it

Forums and newsgroups use ROT13 for spoilers and puzzle answers. Geocaching hints are stored in ROT13. Puzzle hunts, escape rooms and capture-the-flag security challenges use it as an easy first layer. Programmers meet it as a classic exercise in character manipulation, and it appears in some older software to obscure, not protect, settings.

Not a security tool

ROT13 has no key and only one possible setting, so it can be reversed instantly by anyone. Never use it, or any of these variants, for passwords, personal data or anything confidential. It only hides text from someone who is not trying to read it.

Files and privacy

Open a text file to convert it whole and download the result. Everything happens in your browser.

A worked example

A forum post hides a spoiler as “Gur ohgyre qvq vg.” Pasting it with ROT13 selected gives “The butler did it.” Pasting the result again gives back the hidden version, which is what you post to hide your own spoiler. If the hidden text included the year 2026, ROT13 would leave the digits visible; ROT18 would turn them into 7571, and ROT47 would scramble the punctuation as well.

Telling ROT13 from other ciphers

ROT13 text keeps word lengths, punctuation and capital letters, and its most common letter is usually r, because e is the most common English letter and e shifted by 13 is r. Short words such as gur (the) and naq (and) are tell-tale signs. If those clues are missing, try the Caesar Cipher Solver, which tests every shift, not just 13.

Related tools

Try other shifts and crack them with the Caesar Cipher Solver, reverse the alphabet with the Atbash Cipher, use a keyword with the Vigenère Cipher, or encode data for transport with the Base64 Encoder.