Random Number Generator
Cryptographically Random Number Tool
Generate a list of random integers or decimals within a custom range, powered by your browser's cryptographically secure random number generator.
Understanding Random Number Generation
Not all "random" numbers are created equal. The source of randomness matters a great deal depending on what you're using the numbers for — from picking a raffle winner to seeding a scientific simulation.
JavaScript's built-in Math.random() is a fast pseudo-random generator — its output is determined by an internal seed and algorithm, so it's not designed to resist prediction. crypto.getRandomValues(), which this tool uses, draws entropy from the operating system's cryptographically secure random number generator, producing values that are unpredictable even to an attacker who has seen previous outputs.
Random number generators are used for raffles and giveaways, drawing a random sample from a larger dataset, generating test data, shuffling game elements, and picking lottery-style numbers. Whenever fairness matters, a cryptographically secure source is the safer choice.
Why crypto.getRandomValues?
Every number this calculator generates is drawn using the browser's crypto.getRandomValues() API — the same cryptographically secure source used for generating encryption keys and session tokens. Unlike Math.random(), which prioritizes speed over unpredictability, crypto.getRandomValues() is built specifically so that its output cannot be feasibly predicted, even by someone who knows the algorithm and has observed prior results. That makes it the right choice whenever the outcome needs to be genuinely fair, such as picking a raffle winner or shuffling a deck for a game with real stakes.
Choosing Your Options
Use Integer mode for whole-number scenarios like dice rolls, lottery numbers, or random IDs. Use Decimal mode when you need fractional precision, such as generating sample measurements or simulated sensor readings. Unchecking Allow Duplicates guarantees every value in the list is distinct — useful for drawing unique raffle tickets or sampling without replacement — but the range must contain at least as many distinct values as the count you request. Sort Output simply reorders the finished list; it has no effect on which numbers are drawn.
Key Takeaways
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Cryptographically secure. Every number is drawn with
crypto.getRandomValues(), not the predictableMath.random(). - Integers or decimals. Switch modes depending on whether you need whole numbers or fractional precision.
- Unique draws are supported. Disable duplicates for sampling without replacement, as long as the range can hold enough distinct values.
- Need the odds instead? Use the Probability Calculator to work out the chance of a specific outcome.
Frequently Asked Questions
- Enter a Minimum and Maximum value for the range.
- Enter How Many numbers you want generated.
- Choose Integer or Decimal for the Number Type. If you pick Decimal, set how many decimal places to round to.
- Optionally uncheck Allow Duplicates to force every generated number to be unique, and choose a Sort Output order.
- Click "Generate" to see your list of random numbers.
Integer mode generates whole numbers only, rounding the range inward to the nearest whole number at each end. Decimal mode generates fractional numbers within the exact range you enter, rounded to the number of decimal places you choose (e.g. 2 decimal places gives values like 4.17).
When checked (the default), the same number can appear more than once in the generated list — like rolling a die multiple times. When unchecked, every number in the list is guaranteed to be unique. Unchecking it requires the range to actually contain enough distinct values for the count you requested; otherwise the calculator shows an error, since it's mathematically impossible to draw more unique numbers than exist in the range.
This generator draws its randomness from the browser's crypto.getRandomValues API instead of JavaScript's built-in Math.random(). Math.random() is a fast pseudo-random generator that is not designed to be unpredictable — its internal state can potentially be inferred from enough outputs. crypto.getRandomValues pulls from the operating system's cryptographically secure random number generator, making it suitable for raffles, giveaways, sampling, and any use case where fairness and unpredictability actually matter.
By default ("None"), numbers are listed in the order they were generated. Choosing "Ascending" sorts the resulting list from smallest to largest before displaying it — useful when you want to read off the lowest or highest draw at a glance, such as picking lottery-style numbers.
Yes. The Minimum and Maximum fields accept any numeric value, including negative numbers and decimals. In Integer mode the range is rounded inward to the nearest whole numbers before drawing; in Decimal mode the exact range you enter is used.