How to use the ROT13 Encoder / Decoder
1. Type or paste your text in the left panel.
2. The ROT13 encoded (or decoded) text appears instantly on the right.
3. ROT13 is self-reversing — apply it twice to recover the original. Click Copy to save the result.
What is it?
ROT13 (Rotate by 13) is a simple letter substitution cipher that shifts each letter 13 positions forward in the alphabet. Because the alphabet has 26 letters, applying ROT13 twice returns to the original text — making the same operation work for both encoding and decoding. A becomes N, B becomes O, Z becomes M, and so on. Non-letter characters (numbers, punctuation, spaces) pass through unchanged.
ROT13 is not cryptographically secure and should never be used for actual security. It is used on the internet to obscure spoilers, punchlines, and puzzle answers so readers can choose whether to reveal them. It's also used in some simple obfuscation scenarios and is commonly seen in developer forums and bulletin boards.
Example
Gur ohgyre qvq vg va gur xvgpura.
The butler did it in the kitchen.
ROT13 is self-reversing — encode and decode use the exact same operation. Apply twice to recover original text.
Benefits
Hide spoilers, puzzle answers, and solutions in text
ROT13 is the standard format for obscuring text that readers can choose to reveal — used across forums, FAQs, and puzzle sites.
Encode and decode in a single step
Applying ROT13 twice returns the original text — the same tool and the same operation works in both directions.
Reveal ROT13-wrapped content from Reddit, forums, and FAQs
Decode ROT13-obscured spoiler text from any site that uses it for optional content protection.
Explore Caesar cipher mechanics interactively
ROT13 demonstrates the fundamental substitution cipher concept in the simplest possible form — no key management, no setup.
Frequently asked questions
Is ROT13 the same as encoding and decoding?
Yes — ROT13 is self-reversing. Encoding with ROT13 produces the cipher text; applying ROT13 again to the cipher text recovers the original. This is why the same operation works for both encoding and decoding. You never need to switch modes.
Are numbers and punctuation affected?
No — ROT13 only affects ASCII letters (A–Z and a–z). Digits (0–9), spaces, punctuation, and non-ASCII characters (emoji, accented letters) pass through completely unchanged. This makes ROT13 safe to apply to most text without losing structure.
What is the difference between ROT13 and Caesar cipher?
Caesar cipher is a generalization of ROT-N where N can be any number 1–25. ROT13 is specifically the Caesar cipher with N=13. The special property of ROT13 (self-reversing) comes only from N=13, because 13+13=26 (the alphabet length). No other Caesar shift has this property.