ROT13 Converter — Free Online Tool
What is ROT13 Converter?
The ROT13 Converter is a specialized text processor that applies a classic substitution cipher, replacing every letter in your text with the 13th letter after it in the alphabet. Because the English alphabet possesses exactly 26 letters, ROT13 is brilliantly symmetric: applying the cipher a second time completely undoes the encryption, restoring your original text.
While offering zero actual cryptographic security, it has served as the internet's standard 'spoiler warning' mechanism for decades, safely obfuscating movie endings, puzzle solutions, and punchlines.
When to use ROT13 Converter?
Use this tool to obscure text on public forums, Discord channels, or social media pages to prevent casual readers from accidentally seeing a movie spoiler or puzzle solution. They must consciously choose to decode it.
Because the same code handles both encoding and decoding, you don't need a separate tool to read a message you received. If you want a more complex cipher approach, consider using the Hex to Text Converter to serialize your data into machine language.
How to use this tool
- 1Paste your text
- 2Click 'Convert' (works for both encoding and decoding)
- 3Copy the ROT13 output
There is no 'encode' or 'decode' toggle. Just paste the text. If you paste English, it becomes a cipher. If you paste a cipher, it becomes English.
Examples
| Input | Output |
|---|---|
| Hello World | Uryyb Jbeyq |
| Uryyb Jbeyq | Hello World (decoded) |
| ROT13 is fun | EBG13 vf sha |
| ABCDEFGHIJKLM | NOPQRSTUVWXYZ |
| Spoiler: character dies | Fcbvyre: punenpgre qvrf |
Rules & Behavior
- The tool shifts each alphabetical letter exactly 13 positions forward. An 'A' becomes an 'N', a 'B' becomes an 'O', and a 'Z' wraps around to become an 'M'.
- Because 13 + 13 = 26, the function is entirely reciprocal. Running the result back through the tool reverses the translation perfectly.
- Numbers, whitespace, and punctuation symbols are completely ignored and preserved exactly as they were in the original text.
Related Tools
Frequently Asked Questions
What is ROT13?
ROT13 (Rotate by 13 places) is a simple substitution cipher. It replaces a letter with the 13th letter after it in the alphabet. It was historically used on early internet message boards (Usenet) to hide punchlines, offensive content, or movie spoilers so people didn't read them by accident.
How do I decode ROT13?
You use the exact same tool! Because the alphabet has 26 letters, moving forward 13 spaces twice brings you back to exactly where you started. To decode a ROT13 message, simply paste it into the converter and click the button to reverse it back to English.
Is ROT13 a secure form of encryption?
Absolutely not. ROT13 provides zero real security. It has no password, no secret key, and can be broken instantly by a human or a computer. It is strictly for casual obfuscation (like hiding a puzzle answer), never for protecting personal data or passwords.
Does it change numbers or punctuation?
No. The ROT13 algorithm specifically targets the 26 letters of the English alphabet. All numbers (0-9), spaces, commas, emojis, and special symbols are completely ignored and remain perfectly legible in the output string.
Does ROT13 preserve capital letters?
Yes. The algorithm respects the original casing. If you input a capital 'A', it shifts to a capital 'N'. If you input a lowercase 'a', it shifts to a lowercase 'n'. You can safely use the Title Case Converter beforehand knowing the formatting won't be ruined.