BrowserTools

ROT13 Encoder / Decoder

Classic ROT13 letter rotation cipher

By Guga — BrowserTools maintainer, Tbilisi, Georgia Updated 2026-09-01
Free Private No uploads
What is ROT13 Encoder / Decoder?

ROT13 rotates every English letter thirteen places through the alphabet, wrapping Z round to A. The property that makes it unusual is that thirteen is exactly half of twenty-six, so running the text through twice returns the original — the encode button and the decode button are the same button. It was invented to hide plot spoilers and puzzle answers on forums where a reader could choose to look, which is exactly the scale of security it offers: none at all. Anyone can reverse it instantly, and automated tools do so without being asked. The mapping touches ASCII letters only, so Cyrillic, Greek, accented characters and emoji pass through untouched, while digits, spaces and punctuation are left alone.

Apply the classic ROT13 cipher — each letter is shifted 13 places, so encoding and decoding are the same operation. The original spoiler-hider of early internet forums.

Private ROT13 Encoder / Decoder In Your Browser

ROT13 Encoder / Decoder is processed locally with client-side JavaScript. Your files never touch a server, and there is no queue to wait in.

Step-by-Step

How to use ROT13 Encoder / Decoder

1

Paste the text you want to obscure into the input box.

2

Click Apply ROT13 — the result appears in the panel below immediately.

3

Read the transformed text, which is safe to post publicly as a spoiler.

4

Paste the ROT13 text back in and apply it again to recover the original.

Key Capabilities
  • Single transform that both encodes and decodes, since two passes are the identity
  • Applies only to English letters, leaving digits, spaces and punctuation unchanged
  • Non-Latin scripts, accents and emoji pass through without alteration
  • Result refreshes as you type, with a copy control on the output
Common Use Cases
  • A forum moderator obfuscating a plot twist so a reader has to choose to reveal it.
  • A puzzle setter posting an answer that casual readers will not see by accident.
  • A developer testing whether a system correctly decodes ROT13 in a legacy text protocol.
Clear Answers

Frequently Asked Questions

Is ROT13 encryption?
No, and the difference matters if you are relying on it. Encryption requires a key and is designed to resist someone who knows the algorithm was used. ROT13 has no key, is public knowledge, and reverses with the same operation that produced it. It hides a spoiler from an inattentive reader; it protects nothing from anyone who is actually curious.
Why does the same button do both jobs?
Because thirteen is half of twenty-six. Every letter moves to the opposite side of the alphabet, so moving it thirteen more places lands it back where it started. Apply it twice and the text is identical, which is a property of the alphabet length rather than of this implementation.
What happens to non-English characters?
They are left exactly as they were. The rotation is defined over a to z and A to Z, so Cyrillic, Greek, accented letters and emoji all pass through untouched while the English letters around them shift. A mixed message is therefore partly hidden and partly readable, which is a limitation worth knowing about.
How strong is the obfuscation on a mixed message?
Weak, in a specific way. Digits, punctuation and any non-Latin characters survive unchanged, so a message can often be guessed from its shape even when the letters are scrambled. If you need something genuinely private, use a real cipher or put it behind a login.