Last updated: March 2026
How Random Number Generators Work
Not all randomness is created equal. Most programming languages include a basic random function — JavaScript's Math.random() — but these generate pseudo-random numbers. They use mathematical formulas (like linear congruential generators) that produce sequences that look random but are actually deterministic. If you know the seed, you can predict every number.
True random number generation relies on physical phenomena like atmospheric noise. Pseudorandom generators used in software can produce sequences that pass statistical randomness tests.
Our generator uses crypto.getRandomValues(), the Web Cryptography API built into every modern browser. This pulls entropy from hardware sources — mouse movements, keyboard timings, system interrupts, and dedicated hardware random number generators found in modern CPUs. The result is cryptographically secure randomness that's suitable for security-sensitive applications.
The difference matters for anything beyond casual use. Raffles and giveaways need provably fair randomness that participants can trust. Generating passwords or tokens requires unpredictable output. Even games and simulations benefit from better randomness — pseudo-random generators can produce subtle patterns that affect outcomes.
For most everyday uses — picking a random number for a game, deciding who goes first, or generating a lottery pick — both types of randomness work fine. But since cryptographic randomness costs nothing extra in performance, there's no reason not to use it. Our generator gives you the best available randomness your browser can produce.
Frequently Asked Questions
How random are the numbers?
We use crypto.getRandomValues(), a cryptographically secure random number generator built into your browser. It's significantly better than Math.random() and suitable for applications requiring true randomness.
Can I generate numbers without duplicates?
Yes. Uncheck 'Allow duplicates' and the generator will ensure every number in your result is unique. Note: the range must be large enough to accommodate the quantity of unique numbers requested.
What's the maximum range?
You can set any integer range. For practical purposes, we recommend keeping the range reasonable (up to millions). The generator handles large ranges efficiently using cryptographic randomness.
Can I generate decimal numbers?
Yes. Uncheck 'Integers only' to generate random decimal numbers with two decimal places within your specified range.
What dice types are available?
d4, d6, d8, d10, d12, d20, and d100. You can roll up to 20 dice at once. The d6 shows traditional dot faces.
Is the coin flip fair?
Yes. Each flip uses crypto.getRandomValues() for a true 50/50 chance. The cumulative statistics will approach 50% over many flips.