Random Number Generator

What the Random Number Generator Does

This tool generates one or more random whole numbers between a minimum and maximum you choose, both ends included. You can ask for many at once, and optionally require them all to be different, drawing without replacement.

It is the quick way to pick a winner, roll a number, sample from a list by index, or seed a decision — anywhere you want a fair, unpredictable number rather than a guessable one.

How It Works

For each number, the tool takes a value from the browser's cryptographic random generator and maps it into your range, so every value from the minimum to the maximum is equally likely. This is a secure source, unlike ordinary random functions, which means the results cannot be predicted or reproduced.

With the unique option on, it draws from a pool of the possible values and removes each one as it is picked, so no number repeats. That works as long as the range is at least as large as the count you ask for; otherwise repeats are unavoidable.

Generation algorithm

1. Read the range and count. Take the minimum, maximum and how many numbers you want.
2. Draw secure randomness. Get a value from the browser's cryptographic random generator for each pick.
3. Map into the range. Scale each value to a whole number between the minimum and maximum, inclusive.
4. Apply unique if set. If unique is on, draw without replacement so no number repeats.

Random pick in a range

The range is inclusive of both min and max. Unique mode needs the range to hold at least as many values as you request, or numbers will have to repeat.

Standards & references

• Cryptographically secure randomness — The numbers come from the browser's CSPRNG (crypto.getRandomValues), a secure source. Ordinary pseudo-random functions like Math.random are predictable and unsuitable where fairness or unpredictability matters.
• Uniform distribution — Each value in the range is equally likely, so the draw is fair. Over many picks the spread is even, with no bias toward any part of the range.
• Drawing without replacement — The unique option models drawing from a pool and removing each pick, like a raffle, so no number repeats — provided the range is large enough for the count.

Accuracy & Limitations

Because the randomness is cryptographically secure, the numbers are unpredictable and the draw is genuinely fair — a real advantage over tools built on ordinary random functions, which can be predicted or repeated.

The range is inclusive of both ends, so a range of 1 to 100 can return 1 or 100. Make sure the bounds are the ones you intend, as off-by-one expectations are the most common surprise.

Unique mode requires the range to hold at least as many distinct values as you ask for. Request more numbers than the range allows and repeats become unavoidable, so widen the range or lower the count.

It generates whole numbers. For decimals, fractional outcomes or weighted choices, a different setup is needed — this tool draws evenly across the integers in your range.

Real-World Use Cases

When to use it — and when not to

For a secret key or token, use a random token generator that outputs bytes in hex or Base64. For decimals or weighted picks, a custom calculation is needed. This tool draws whole numbers evenly across a range.

Frequently Asked Questions

References

• Crypto.getRandomValues (MDN Web Docs)
• Cryptographically secure pseudorandom number generator (Wikipedia)
• Discrete uniform distribution (Wikipedia)

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