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ROT13 Encoder / Decoder

Encode text to ROT13 quickly and privately. The conversion runs in your browser.

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What is ROT13?

ROT13 is a reversible letter substitution cipher that shifts each letter 13 positions forward in the alphabet, making decryption identical to encryption. This free, browser-based ROT13 Encoder/Decoder lets you instantly convert text to and from ROT13 cipher without uploading anything—everything runs locally on your device for complete privacy. Perfect for hiding spoilers, puzzle answers, sensitive jokes, or learning encryption basics, ROT13 offers simplicity over security and works on any device with a web browser.

How ROT13 works

ROT13 replaces each letter with the letter exactly 13 positions ahead in the alphabet, wrapping around when necessary. Since the alphabet has 26 letters, applying ROT13 twice returns the original text—making encoding and decoding the same operation.

The Mapping:

A→N, B→O, C→P, D→Q, E→R, F→S, G→T, H→U, I→V, J→W, K→X, L→Y, M→Z, N→A, O→B, P→C, Q→D, R→E, S→F, T→G, U→H, V→I, W→J, X→K, Y→L, Z→M

Worked Example:

Input: "Hello World"

Apply ROT13 to each letter:

  • H (position 8) → U (position 21)
  • e (position 5) → r (position 18)
  • l (position 12) → y (position 25)
  • l (position 12) → y (position 25)
  • o (position 15) → b (position 2)
  • W (position 23) → J (position 10)
  • o (position 15) → b (position 2)
  • r (position 18) → e (position 5)
  • l (position 12) → y (position 25)
  • d (position 4) → q (position 17)

Output: "Uryyb Jbeyq"

Numbers and special characters remain unchanged. Apply ROT13 again to "Uryyb Jbeyq" and you get "Hello World" back.

How to use

  1. Enter or paste your text in the input box.
  2. The ROT13-encoded result appears instantly in the output.
  3. Click Copy to use the encoded value.

Common uses

  • Hide spoilers and puzzle answers in online forums and discussions without spoiling others
  • Obscure mildly sensitive jokes and content from casual viewing in comment sections
  • Teach encryption fundamentals and understand how substitution ciphers work
  • Decode ROT13 messages received from friends or online communities using the same tool
  • Preserve text formatting while converting between encoded and readable formats instantly
  • Process unlimited text with no length restrictions or account requirements

Frequently asked questions

Is my text secure with ROT13?
No. ROT13 provides no real cryptographic security and is trivially easy to break. Use it only to lightly obscure content, not to protect sensitive information. For actual security, use proper encryption like AES.
Do you store my data?
No. This tool runs entirely in your browser—nothing is uploaded to our servers. Your text never leaves your device, ensuring complete privacy.
Can I encode numbers and special characters?
ROT13 only rotates the 26 letters of the alphabet (A-Z). Numbers, spaces, punctuation, and symbols remain unchanged. Variants like ROT5 exist for numbers specifically.
Why is it called ROT13 if it shifts by 13?
ROT stands for 'rotation' and 13 refers to the number of positions each letter shifts forward in the 26-letter alphabet. 13 is special because shifting twice (26 total positions) returns the original text.
What are common uses for ROT13?
ROT13 is commonly used on forums to hide joke punchlines, spoilers for movies and books, puzzle solutions, and offensive material from casual glance. It's also used educationally to teach cipher basics.
Is ROT13 the same as a Caesar cipher?
ROT13 is a special case of the Caesar cipher with a fixed shift of 13. A Caesar cipher can use any shift value (1-25), while ROT13 uses specifically 13.