ROT13, the involutive Caesar shift
ROT13 is a special case of the Caesar cipher with a fixed shift of 13. Each letter a-z and A-Z moves forward 13 positions through the 26-letter Latin alphabet, wrapping at the end. Because 13 + 13 = 26, applying ROT13 twice gets you back to where you started. That property (involutive) is what makes ROT13 useful as a one-button "spoiler hide" on forums and Usenet: same encode and decode operation.
Only ASCII letters move. Digits 0-9, ASCII punctuation, whitespace, accented Latin characters (café, résumé), and any non-Latin script (Cyrillic, Greek, CJK, emoji) all pass through unchanged. So Café 4821 becomes Pnsé 4821 (the é stays put because it is not in the a-z A-Z range).
ROT13 is not encryption. It is trivially reversible by anyone who knows what ROT13 is, and Google search literally previews ROT13 text. Use it for spoilers, Easter eggs, light obfuscation in puzzle text, and as a teaching example of substitution ciphers. For an arbitrary shift, use Caesar cipher; for the alphabet-reversal cipher, see Atbash.
How to use rot13 cipher
- 1Paste or type your text into the input panel on the left.
- 2The ROT13 result appears in the output panel on the right as you type.
- 3Apply ROT13 again to decode (the cipher is its own inverse).
- 4Click Copy in the output header to copy the result.
- 5For a different shift, use Caesar cipher with a custom Shift value.
Keyboard shortcuts
Drive TextResult without touching the mouse.
| Shortcut | Action |
|---|---|
| Ctrl F | Open the find & replace panel inside the input Plus |
| Ctrl Z | Undo the last input change |
| Ctrl Shift Z | Redo |
| Ctrl Shift Enter | Toggle fullscreen focus on the editor Plus |
| Esc | Close find & replace, or exit fullscreen |
| Ctrl K | Open the command palette to jump to any tool Plus |
| Ctrl S | Save current workflow draft Plus |
| Ctrl P | Run a saved workflow Plus |
What this tool actually does
Caesar shift of 13 on ASCII letters
Each a-z and A-Z letter shifts forward 13 positions, wrapping at the end of the alphabet. a -> n, n -> a, m -> z, z -> m. Case is preserved.
Self-inverse: encode and decode are the same
Because 13 + 13 = 26, applying ROT13 twice returns the original. There is no separate decode button. This is the cipher's defining feature and the reason it exists as a single named function.
Non-letters pass through unchanged
Digits 0-9, punctuation, whitespace, accented Latin characters (é, ñ), and non-Latin scripts (Greek, Cyrillic, CJK, emoji) are not transformed. Only the ASCII a-z A-Z range moves.
No options, no configuration
ROT13 has no settings. The shift is locked at 13. For variable shifts, switch to Caesar cipher, which exposes a Shift field with range -25 to 25.
Not encryption
ROT13 is reversible by anyone who knows the algorithm. It hides text from a casual eye but offers no security. Use it for spoilers, puzzles, and as an introduction to how substitution ciphers work, not for anything that needs to stay secret.
Worked example
Letters shift 13 places; the . and the spaces pass through. Apply ROT13 to the output and you get the input back. For arbitrary shifts, see Caesar cipher.
The quick brown fox jumps over the lazy dog.
Gur dhvpx oebja sbk whzcf bire gur ynml qbt.
Settings reference
| Behaviour | Effect on output |
|---|---|
ASCII a-z letters |
Shift forward 13 positions. a -> n, z -> m. |
ASCII A-Z letters |
Shift forward 13 positions, case preserved. |
Digits 0-9 |
Pass through unchanged. |
| Punctuation and whitespace | Pass through unchanged. |
| Accented Latin characters | é, ñ, ü pass through unchanged. ROT13 is ASCII-only. |
| Non-Latin scripts | Cyrillic, Greek, CJK, emoji all pass through unchanged. |
| Self-inverse | Apply ROT13 twice to get the original input back. |
FAQ
How do I decode ROT13?
Does ROT13 affect numbers or punctuation?
a-z and A-Z shift. Digits, punctuation, whitespace, and accented characters all pass through unchanged. So ORDER #4821 becomes BEQRE #4821.