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ROT13 Encoder & Decoder

Input
Output
Go to the full Classical Cipher Encoder

ROT13 shift

HELLO becomes URYYB. Every letter moves 13 places forward, and non-letter characters pass through unchanged.

Self-inverse

Applying ROT13 to URYYB again returns HELLO. Because 13 doubled is 26, the full length of the alphabet, encoding and decoding land on the exact same transformation.

Typical use

ROT13 hides text just enough that it does not read at a glance, which made it a common way to mask spoilers, quiz answers, or offensive words in plain-text forums before spoiler tags existed. It has never been intended to protect anything from a determined reader.

Frequently Asked Questions

It shifts every letter 13 positions forward in the alphabet, wrapping from Z back to A. Numbers, spaces, and punctuation are left unchanged.

13 is exactly half of the 26-letter alphabet, so shifting by 13 twice returns every letter to its original position. Encoding and decoding are the same operation.

Hiding spoilers, puzzle answers, or punchlines from a casual glance in forum posts and old Usenet threads. It provides no real security, since the shift amount is fixed and publicly known.

Try one of these focused ciphers

Full Classical Cipher Encoder tool
001 Caesar Cipher Encoder & Decoder
002 ROT47 Encoder & Decoder

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