Cryptographically random numbers, with filters
Generate one or many random numbers, either within a min/max range or with an exact digit length, with optional filters for even/odd only or no repeated digit within a number. Uses the Web Crypto API for genuine randomness where your browser supports it.
How to use
- Choose range mode or exact-digit-length mode
- Set your range or length, and any filters (parity, no repeated digits)
- Press Generate — repeat for a fresh set any time
Common questions
Where does the randomness actually come from — is it good enough to trust?
It uses the Web Crypto API's cryptographically secure random number generator when available (with rejection sampling to remove any modulo bias), falling back to Math.random() only if Web Crypto isn't present in your browser.
What does "no repeated digits" mean exactly?
It means no digit repeats within a single generated number, not that two numbers in the same batch can't match each other. For example, with this on, 1234 is allowed but 1123 is not.
Why can't I generate a 12-digit number with no repeated digits?
There are only 10 possible digits (0–9), so any number longer than 10 digits is mathematically guaranteed to repeat at least one. The no-repeat option is capped at 10 digits for this reason; length mode itself still allows up to 12 digits with repeats permitted.