ROT13 Encoder / Decoder

ROT13 Encoder / Decoder — Free online ROT13 encoder and decoder. Encode or decode any text instantly with ROT13, ROT5, ROT18, or ROT47. Since ROT13 is its own inverse, the same tool encodes and decodes.

Letters only↔ encode = decode

0Input length

0Rotated chars

ROT13Variant

Letters onlyScope

Input

Output

Input

Output

How to encode and decode ROT13

Paste your text into the input box. The encoded output appears instantly on the right.
Choose a variant — ROT13 for letters, ROT5 for digits, ROT18 for both, or ROT47 for all printable ASCII characters.
To decode, paste the encoded text — the same tool decodes it. ROT13 is its own inverse: encoding twice returns the original.
Use “Use output as input” to chain operations or quickly swap input and output.

ROT variants explained

Variant	Shift	Affects	Example
ROT13	13	Letters A–Z	Hello → Uryyb
ROT5	5	Digits 0–9	12345 → 67890
ROT18	13/5	Letters + digits	abc123 → nop678
ROT47	47	All printable ASCII (33–126)	Hello! → w6==@ 6

When ROT13 is used

Hiding spoilers

The original Usenet use case. Encode spoilers so readers must actively decode them.

Puzzle and CTF challenges

ROT13 is a common beginner-level cipher in Capture The Flag competitions.

Email obfuscation

Lightly obscure email addresses or names in public text to slow automated scrapers.

Forum and blog conventions

Many communities use ROT13 for off-topic jokes or answers that others may not want to see.

For stronger encoding, try Base64 Encode / Decode or Morse Code Translator for a different kind of text transformation.

Learn more about ROT13

Want the full substitution table, the math behind why encoding twice restores the original, and how ROT13 compares to the Caesar cipher? What Is ROT13? has the complete breakdown.

Frequently Asked Questions

What is ROT13?

ROT13 (rotate by 13) is a simple letter substitution cipher that replaces each letter with the letter 13 positions ahead of it in the alphabet. Since the alphabet has 26 letters, applying ROT13 twice returns the original text — making it its own inverse.

How do I decode ROT13?

Just paste the encoded text and it decodes instantly. ROT13 encoding and decoding are the same operation — applying it once encodes, applying it again decodes.

What is the difference between ROT13, ROT5, ROT18, and ROT47?

ROT13 rotates letters only (A–Z). ROT5 rotates digits only (0–9). ROT18 rotates both letters and digits simultaneously. ROT47 rotates all 94 printable ASCII characters (letters, digits, symbols).

What was ROT13 historically used for?

ROT13 was widely used on Usenet newsgroups in the 1980s and 90s to hide spoilers, offensive jokes, or puzzle answers. It obscures text just enough to prevent casual reading, without any encryption overhead.

Is ROT13 a secure encryption method?

No. ROT13 provides zero security — any basic cipher tool can decode it immediately. It is useful only for casual text obfuscation, hiding spoilers, or puzzles where the goal is not secrecy but a mild barrier to casual reading.