Random Number Generator

True Random vs Pseudo-Random

This generator uses your browser's built-in pseudo-random number generator (PRNG) — specifically Math.random(), which implements an algorithm like xorshift or a similar fast PRNG. PRNGs produce sequences that look random but are deterministic given a starting seed. For raffles, games, demos, and homework, that's more than enough. For cryptography or unpredictability-critical use, switch to crypto.getRandomValues(), which pulls from operating-system entropy sources.

For true physically-random numbers (from atmospheric noise or quantum sources), random.org is the standard reference — they generate true randomness from atmospheric radio noise and have been operating since 1998.

Common Uses

• Lottery number picker — set count to the number of balls, range to the maximum number
• Raffle / draw winner — set count to 1, range to total entries
• Decision maker — set range 1-2 and let chance decide
• Statistical sampling — generate N unique values across a population
• Random group assignment — shuffle a list, split into groups
• Dice replacement — range 1-6 (or 1-20 for D&D)
• Password generation — better to use the dedicated password generator which uses crypto-strength randomness

The Math of Randomness

With n equally likely outcomes, each has probability 1/n. Multiple independent draws follow combinatorial probability. The Wikipedia article on probability theory covers the foundations.

Frequently Asked Questions