Random number generator

A short history of random numbers

Generating fair random numbers is an old problem. Dice carved from bone were used for games and divination over 4,000 years ago, and lotteries funded public works from the Han dynasty's Great Wall to the early American colonies. The modern era began in 1955 when the RAND Corporation published A Million Random Digits — an entire book of random numbers that scientists used for statistical sampling before computers made generation instant. Today's computers produce randomness either with fast mathematical formulas (pseudo-random) or by drawing on unpredictable physical sources (cryptographically secure), which is what this tool uses.

Cryptographically secure randomness

TextlyPop uses the Web Crypto API's crypto.getRandomValues() function when available in your browser. This provides cryptographically secure random numbers — significantly more unpredictable than the standard Math.random() used by most online tools. Cryptographic randomness means the numbers cannot be predicted even if you know the previous results. This matters for any use case where true fairness is important, such as lotteries, giveaways, or statistical sampling.

Picking a random number from a range

Set a minimum and a maximum, press Generate, and you have your number. Both ends are inclusive, so a range of 1 to 10 can return 1 or 10 as readily as anything between them. Negative minimums are allowed, and so is a range of one number, which will simply return that number every time.

Two settings do most of the work beyond that. Count asks for several numbers at once rather than one, which is what you want when drawing multiple raffle winners or generating a set of test values. No repeats makes those numbers unique, turning the generator into a randomizer that draws without replacement — the right mode for picking 6 lottery numbers from 49, or 5 winners from 200 entries, where the same result appearing twice would be a bug rather than luck. With repeats allowed, each draw is independent and duplicates are entirely normal: in a set of ten numbers from 1 to 10, a repeat is more likely than not.

Common random number ranges

Common uses for random number generation

Teachers use random number generators to call on students fairly, assign seats, or create randomized quizzes. Developers use them to test applications with random data inputs. Game players roll virtual dice for board games, tabletop RPGs, and decision making. Researchers and statisticians use random sampling to select participants from a population. Contest organizers pick winners fairly from a numbered list of entries. Anyone who needs to make a fair unbiased decision between numbered options benefits from a random number generator.

Dice rolling with this tool

Each standard dice type has a quick preset button. Click d6 and Generate for a standard six-sided die. Click d20 for a twenty-sided die used in tabletop RPGs. Set Count to match the number of dice you want to roll simultaneously — set Count to 3 and click d6 to roll 3d6. Enable Show sum to see the total roll value, which is how most dice games work. Enable No repeats when you need each die value to be different.

RNG, randomizer and generator

RNG is simply the abbreviation of random number generator, borrowed from gaming and programming, and a number randomizer is the same device described by what it does to a set rather than how it produces a value. The distinction that actually matters is not the name but the source of the randomness. A pseudo-random generator runs a formula from a starting seed: give it the same seed and it replays the identical sequence, which is useful for reproducible simulations and useless for anything that needs to be unguessable. A cryptographically secure generator draws on unpredictable system entropy instead, so knowing every previous result tells you nothing about the next one. This tool uses the second kind wherever the browser provides it.

For randomness in other shapes, the password generator applies the same secure source to characters rather than digits, the UUID generator produces random version 4 identifiers, and the text line sorter has a shuffle mode for putting a list of names or items into random order.

Frequently asked questions