About RandomNumber

RandomNumber makes random choices for the everyday situations that need one: a number between 1 and 100, a winner from a list of giveaway entries, a fair split of a class into teams, a roll of three dice or a password nobody else could guess. Each tool shows what it drew and what the chances were, and each page explains how the result was made, so you can judge for yourself whether it is fair.

The tools

Numbers, letters and dates

• Random number generator: Whole numbers or decimals between any two values, one at a time or as a list, with or without repeats.
• Lottery number generator: Up to 20 lines at a time for six major games or a game you set up, with the main numbers sorted and the bonus balls kept apart.
• Random letter generator: One letter or a row of them, from the whole alphabet, the vowels or the consonants, each with the same chance.
• Random date generator: One date or a list between any two days, both ends included, with every day in the range equally likely.

Dice, coins and cards

• Dice roller: Any number of dice with any number of sides, written as fields or as notation, with the exact chance of the total.
• Coin flip: Heads or tails for one coin, a handful or 10,000, or a best-of-three series, with the odds of what came up.
• Random card generator: Cards dealt from a shuffled standard deck, one at a time or as a hand, with no card repeated.

Names, lists and teams

• Random name picker: Paste the names, choose how many winners, and draw. Every entry has the same chance, and the list never leaves your browser.
• List randomizer: Paste names, tasks or anything else, one per line, and get them back in a random order where every arrangement has the same chance.
• Random team generator: Paste the names, choose how many teams or how many people in each, and get random teams whose sizes differ by at most one.

Passwords and identifiers

• Password generator: Random passwords of any length from 8 to 128 characters, or passphrases of 3 to 10 words, with the strength of each worked out exactly.
• PIN generator: Random PINs of 3 to 12 digits, one or up to 100 at a time, with the most guessable patterns left out if you wish.
• UUID generator: Version 4 (random) and version 7 (time-ordered) UUIDs, one or up to 1,000 at a time, in the format your code expects.

The guides explain the ideas behind them, from how computers make random numbers to how to run a draw that entrants can trust.

Where the randomness comes from

Every tool draws from the cryptographic random number generator built into your browser, the Web Crypto API’s getRandomValues(). Browsers use it for encryption keys, and it is seeded by your device’s operating system from unpredictable hardware events. We do not use Math.random(), which browsers are not required to make unpredictable.

Turning random bits into a number from 1 to 6 or a winner from 250 names is where many generators go subtly wrong. Our tools use rejection sampling, which discards the few random values that would make some outcomes more likely than others, and the Fisher–Yates method for shuffles, so every number, card, name and order has exactly the same chance. The guide to fair shuffling and modulo bias shows why this matters with worked examples.

Your privacy

Everything is generated on your device. The numbers you draw, the names you paste and the passwords you create are not sent to us or stored by us. Some tools put their settings in the address bar so that you can share or bookmark them; they never put your results, names or passwords there. The privacy policy describes the analytics and advertising that the site itself uses.

How the tools are checked

The shared random number code is tested statistically: millions of draws for ranges such as 1 to 2, 1 to 6, 1 to 7, 1 to 100 and 1 to 1,000 are checked with a chi-squared test, and every ordering of a shuffled list is counted to confirm that each comes up equally often. The odds shown on each page are calculated exactly from the number of possible outcomes, and the worked examples are checked against the tool’s output. Facts from outside sources, such as lottery rules and password guidance, are checked against the organisation that publishes them, and each guide lists its sources.

Corrections

If a result or an explanation looks wrong, tell us the page, the settings you used and what you expected. We check every report, fix the tool or the text when we have made a mistake, and reply with what we found.

The company that publishes RandomNumber is identified in our privacy policy. You can reach us at [email protected].