How it works
Rotate ASCII A–Z and a–z by the signed shift modulo 26; preserve other characters.
Input definitions
- Text
- Plain text; maximum 200,000 characters.
- Signed shift (whole number)
- Enter the value in the labeled unit.
A worked example
- Text
- Hello, World!
- Signed shift (whole number)
- 13
Assumptions & limits
Educational substitution cipher; not secure encryption. Apply the negative shift to decode. ROT13 is its own inverse.
Sources & review
Maintained by AnsRio. Methods and examples use automated checks; this does not imply independent professional certification.
Method updated 2026-10-17. Content checked against the stated method and examples. Our verification approach.
Common questions
Is ROT13 secure encryption?
No. ROT13 and Caesar shifts are reversible substitutions with very few possibilities. They are suitable for puzzles and obfuscation, not secrets or passwords.
Can I paste formatted documents into this text tool?
The tool processes plain text. Styling, document structure and rich-text metadata are not preserved. Copy the result before closing the page.
How does the Caesar cipher and ROT13 tool work?
Rotate ASCII A–Z and a–z by the signed shift modulo 26; preserve other characters.
What are the assumptions and limits of Caesar cipher and ROT13?
Educational substitution cipher; not secure encryption. Apply the negative shift to decode. ROT13 is its own inverse.