Real Random Number Generator

Pick a real physical phenomenon from the world around you, and watch a number get pulled out of it, live.

How the generator works

Each request gathers fresh entropy from the chosen source, mixes it with a secret server-side key, and then maps it into your requested range with rejection sampling so every value is equally likely.

  • Raw entropy: live quantum data, server timing noise, or your mouse movement.
  • Mixing: the backend combines the bytes with an HMAC-SHA-512 hash using a secret key.
  • Range mapping: it draws the minimum needed bits, rejects values that would bias the distribution, and redraws until the result is fair.