Hello World
Before
Hello World
After
Uryyb Jbeyq
ROT13 Converter
Rotate the alphabet thirteen places—a symmetric cipher where encoding and decoding use the same button.
ROT13 Converter
Letters A–Z rotate 13 places; numbers and symbols stay unchanged.
Plain text or ROT13-encoded text
Encoded or decoded result
Input: 0 chars
Output: 0 chars
Letters transformed: 0
Digits unchanged: 0
Symbols unchanged: 0
Spaces unchanged: 0
Your text stays in your browser — nothing is uploaded.
How to Use
- Paste plain text or already-encoded ROT13 into the input box.
- Choose Encode ROT13 or Decode ROT13 — both apply the same symmetric cipher.
- Toggle Preserve case, Show changed letters, or Highlight transformed characters as needed.
- Use Swap ↔ to move output back to input, then copy, download, or apply ROT13 again to restore the original.
Example
Plain text
Hello World
ROT13
Uryyb Jbeyq
Before and After Examples
Secret Message
Before
Secret Message
After
Frperg Zrffntr
ROT13
Before
ROT13
After
EBG13
Room 101
Before
Room 101
After
Ebbz 101
Apply twice
Step 1
Hello
Step 2 (ROT13)
Uryyb
Step 3 (ROT13 again)
Hello
What This Tool Does
ROT13 Converter rotates each Latin letter thirteen positions in the alphabet. Because thirteen is half of twenty-six, encoding and decoding use the same operation — apply ROT13 twice and the original text returns. Numbers, punctuation, and spaces stay unchanged.
How ROT13 Works
A ↔ N
Each letter maps to the letter thirteen places away in the alphabet.
B ↔ O
The mapping is fixed — no key or password is required.
C ↔ P
Only A–Z and a–z letters are rotated; everything else passes through.
M ↔ Z
The alphabet wraps: after Z comes A again at the thirteenth step.
Lowercase letters are preserved
Uppercase stays uppercase and lowercase stays lowercase in the output.
Numbers and punctuation stay unchanged
Digits, symbols, emoji, and whitespace are copied exactly as typed.
ROT13 Alphabet Reference
Each letter maps to its partner thirteen positions away. Lowercase follows the same pattern: a ↔ n, b ↔ o, and so on.
A–M ↔ N–Z
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
Lowercase
Apply the same pairs to lowercase letters: a ↔ n, b ↔ o, c ↔ p, … m ↔ z.
ROT13 vs Caesar Cipher
ROT13 is a Caesar cipher with a fixed shift of 13. Use this converter for the standard ROT13 alphabet; use the Caesar Cipher Converter when you need a custom shift amount.
| Task | Best tool |
|---|---|
| ROT13 fixed alphabet shift | ROT13 Converter |
| Custom shift amount | Caesar Cipher Converter |
| Puzzle hints | ROT13 Converter |
| Learning substitution ciphers | Caesar Cipher Converter |
Common Uses
Puzzle hints
Spoiler hiding
Forum posts
Classroom cipher demos
Lightweight obfuscation
Word games
CTF warmups
Teaching substitution ciphers
Security Note
ROT13 is not encryption and should not be used for passwords, private data, tokens, or sensitive messages. It is only a simple reversible text transformation.
Popular Workflows
Notes & Limitations
All conversion runs locally in your browser. ROT13 only transforms basic Latin letters A–Z and a–z. Accented letters, Cyrillic, CJK characters, and emoji pass through unchanged.
Frequently Asked Questions
Why is ROT13 its own inverse?
Shifting each letter by 13 twice equals 26 — a full alphabet rotation — so every letter returns to its starting position. That is why encode and decode are the same operation.
Does ROT13 change numbers?
No. Digits 0–9 are copied exactly as typed and never rotated.
Does ROT13 change punctuation?
No. Punctuation, symbols, and special characters pass through unchanged.
Does ROT13 preserve uppercase and lowercase?
Yes. Uppercase letters stay uppercase and lowercase letters stay lowercase in the output when Preserve case is enabled.
Is ROT13 secure?
No. ROT13 is trivial to reverse and provides no real confidentiality. Use it only for casual obfuscation, puzzles, or demos — never for secrets.
How is ROT13 different from Caesar cipher?
ROT13 is a Caesar cipher with a fixed shift of 13. The Caesar Cipher Converter lets you choose any shift amount and explicit encode/decode modes for learning and puzzles.
Can I decode ROT13 with the same tool?
Yes. Paste encoded text and choose Decode ROT13 — or keep Encode ROT13; both apply the same symmetric transformation.
What happens if I apply ROT13 twice?
You get the original text back. Two shifts of 13 restore every letter to its starting position.
Does ROT13 support non-English letters?
Only basic Latin A–Z and a–z are rotated. Accented letters, Cyrillic, Greek, Arabic, CJK, and emoji are left unchanged.
Is my text uploaded?
No. All ROT13 conversion runs entirely in your browser — nothing is sent to a server.
Can I download the result?
Yes. Click Download .txt to save the output as a plain-text file on your device.