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About this tool
Encodes or decodes text using the ROT13 substitution cipher, which shifts each letter by 13 positions in the alphabet.
ROT13 replaces every letter with the one 13 places further along the alphabet, so A becomes N, N becomes A, and 'Hello World' becomes 'Uryyb Jbeyq'. This tool applies that substitution live as you type and copies the result in one click, keeping case and leaving digits, spaces and punctuation untouched. Because 13 is exactly half of 26, encoding and decoding are the same operation — run any text through twice and you get the original back.
Open ROT13 Encoder/Decoder on AltFTool — it loads instantly in your browser.
Paste or type the text you're working with.
Choose how it should be transformed or analyzed.
Copy the finished text into your document or post.
One transform handles encoding and decoding, so you never have to work out which direction you are going.
Numbers, punctuation, emoji and line breaks pass through unaltered, so code snippets and formatting survive the round trip.
Uppercase stays uppercase and lowercase stays lowercase, so names and sentence casing read normally after decoding.
It rotates each letter 13 positions through the 26-letter alphabet: A to N, B to O, and so on, wrapping Z back around to M. Anything that is not an A-Z or a-z letter is left exactly as it was.
Apply ROT13 again. Since 13 + 13 = 26, a second pass returns every letter to where it started, which is why this tool needs no separate decode algorithm.
No. ROT13 is a fixed substitution with no key, so anyone can reverse it instantly and it offers zero protection for passwords, personal data or anything confidential. It exists to hide text from casual glances — spoilers, punchlines, puzzle answers — not from anyone actually looking.
ROT13 is a Caesar cipher with the shift fixed at 13. A general Caesar cipher can use any shift from 1 to 25, and only the shift of 13 has the property that encryption and decryption are the identical operation.