HesapHanem

ROT13 Cipher

What is ROT13?

Result

Uryyb, Jbeyq!

How it is calculated

ROT13 replaces each letter with the letter 13 places later in the 26-letter English alphabet, wrapping around from Z to A: new = (position + 13) mod 26. Because 13 is exactly half of 26, applying the same operation twice returns the original text, so one tool both encodes and decodes. Uppercase stays uppercase and lowercase stays lowercase. Digits, spaces, punctuation and any letters outside A to Z, such as Turkish ç, ğ, ı, ö, ş, ü or accented letters, are left unchanged. ROT13 is a simple obfuscation, not encryption: it is used to hide spoilers or punchlines from a casual glance, and anyone can reverse it.

Worked example

Enter Hello, World! Take each letter in turn: H moves 13 places to U, e to r, l to y, l to y, o to b. The comma and space stay as they are. W becomes J, o becomes b, r becomes e, l becomes y, d becomes q, and the exclamation mark is untouched. The tool outputs Uryyb, Jbeyq!. Paste that back in and you get Hello, World! again.

Try this example →

Common mistakes

  • Treating ROT13 as secure. It has no key and can be undone by anyone in seconds; never use it for passwords or private data.
  • Expecting Turkish or other non-English letters to be shifted. Only the 26 letters A to Z change, so ç, ğ, ı, ö, ş and ü pass through unchanged.
  • Expecting digits to change. ROT13 does not touch numbers; the ROT47 variant handles those.
  • Running it twice and thinking nothing happened. A second pass restores the original text by design.
  • Confusing ROT13 with a Caesar cipher of any shift. ROT13 is a fixed shift of 13 only.

About this calculator

This tool applies ROT13, a simple substitution cipher that shifts every letter 13 positions through the alphabet, wrapping from Z back to A. Because the alphabet has 26 letters, applying the same 13-position shift a second time reverses the first, which is why the identical operation both encodes and decodes any message — there's no separate decrypt step or key to manage.

ROT13 provides no real security since it is trivial to break, so it was never intended to protect sensitive information; instead it is traditionally used on forums and newsgroups to obscure spoilers, puzzle answers, or offensive jokes from someone's screen so readers have to actively choose to decode the text before seeing it. Programmers also use it informally as a lightweight obfuscation for test data, throwaway examples, or hiding an answer key in a document where casual glancing shouldn't reveal it immediately.

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Comments (1)

  • Editorial team

    Once you read a little ROT13 you can decode common words by eye. The becomes gur and and becomes naq, so a short forum spoiler is often legible after a few tries. That also shows why it only hides text from a casual glance. If you hide spoilers or puzzle answers with it, add a plain-language warning above the encoded text. Where do you use ROT13, forums, puzzles or something else?

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