Random Number Generator

How Do Random Number Generators Work?

Computers use pseudorandom number generators (PRNGs) to produce sequences of numbers that appear random. JavaScript’s Math.random() generates a decimal number between 0 (inclusive) and 1 (exclusive). By multiplying and flooring this value, we can produce random integers in any desired range. For example, to get a random number between 1 and 100:Math.floor(Math.random() * 100) + 1.

Pseudorandom numbers are not truly random—they are generated by deterministic algorithms using a seed value. However, for most practical purposes such as games, sampling, and general use, the quality of modern PRNGs is more than sufficient. For cryptographic applications or security-sensitive use cases, cryptographically secure random number generators (CSPRNGs) such as the Web Crypto API should be used instead.

Common Uses for Random Numbers

Random numbers are used extensively across many fields. In gaming, they determine dice rolls, card shuffles, loot drops, and procedural world generation. In statistics and research, random sampling ensures unbiased data collection. In education, random number generators are used to randomly assign students to groups or select quiz questions.

Other common uses include lottery number generation, password generation (when combined with other character sets), A/B testing sample selection, Monte Carlo simulations, and randomized algorithms in computer science. The option to disallow duplicates is useful for lottery-style draws and random selection without replacement, while sorting results makes it easy to verify that the expected range of values was generated.