ROT5 is a tiny substitution cipher for numbers. It rotates each decimal digit by five places, so 0 swaps with 5, 1 with 6, and so on. It is the numeric sibling of the well-known ROT13 letter cipher and is most useful for puzzles, obfuscating order numbers in screenshots, or teaching modular arithmetic. This tool applies ROT5 instantly and leaves all non-digit characters untouched.
How it works
For every character, the tool checks whether it is a digit from 0 to 9. If it is, the new value is (digit + 5) mod 10. That gives the pairs 0↔5, 1↔6, 2↔7, 3↔8 and 4↔9. Any character that is not a digit — a letter, space, or punctuation mark — is copied straight to the output with no change.
Because the rotation amount (5) is exactly half the number of digits (10), ROT5 is a self-inverse operation. Running it twice returns the original text, which is why a single button both encodes and decodes.
Example
The string Order 1234 ships in 7 days becomes Order 6789 ships in 2 days: the digits 1, 2, 3, 4 rotate to 6, 7, 8, 9 and the lone 7 rotates to 2, while every letter and space is preserved.
Notes
ROT5 has no key and a trivially small key space, so it is not encryption — treat it as a puzzle or obfuscation toy. Everything runs locally in your browser; your text is never uploaded.