Random Number Generator

About the Random Number Generator

The random number generator draws numbers from the secure random source built into your browser, the same one used for cryptography, not from Math.random. Each number is made from just enough random bytes to cover the range, and a draw that would favour some values is thrown away and repeated. This matters: a common shortcut takes a random value and keeps the remainder after dividing by the size of the range, and that makes the low values more likely. With one random byte and a range of 6, for example, the values 1 to 4 would come up 43 times in 256 and the values 5 and 6 only 42 times. The tool avoids this, and feeding it every possible byte string shows that every result appears the same number of times. Ranges can be huge, because whole numbers are handled exactly up to 40 digits, and decimals are drawn from an exact grid, so 0 to 1 with 4 decimals has 10,001 equally likely values. The no repeats option never returns the same number twice, and if you ask for more numbers than the range holds it tells you why that is not possible. You can ask for up to 10,000 numbers at once. The generator was tested with a chi-square test on more than 55 million draws, and every p-value was between 0.17 and 0.96, which is what a fair generator gives. For passwords, use the Password Generator instead. Everything runs in your browser and nothing is uploaded.