Random Number Generator

Generated 5 value(s) in [1, 100] from the reproducible seed.

How it works

• Read the range, count and integer/decimal mode.
• Drew bytes from the selected random source.
• Mapped each draw to a distinct range index with a partial Fisher–Yates shuffle.
• Reported the values and whether the source was the CSPRNG or a reproducible seed.

• A seeded run is reproducible by design and must not be used where unpredictability is required.
• Unique mode can never produce a duplicate because it samples without replacement.

Methodology

1. Resolve the random source: the injected or seeded source for reproducible runs, otherwise the platform CSPRNG.
2. Read a 53-bit uniform double from two 32-bit halves, or a uniform integer with rejection sampling to avoid modulo bias.
3. For unique mode, perform a partial Fisher–Yates shuffle over the range indices so no value repeats.
4. Scale the draws into the requested range and round decimals to the requested precision.

Usage

1. Enter the minimum and maximum of the range.
2. Choose how many values you need, and whether they must be unique.
3. Switch off integer mode for decimal values and set the decimal places.
4. Generate and copy the values.

Examples

These are examples, not current values: they use fixed inputs, while the interactive tool computes live results in your browser.

Five unique integers from 1 to 100

{
  "min": 1,
  "max": 100,
  "count": 5,
  "unique": true,
  "seed": "example"
}

Three dice rolls

{
  "min": 1,
  "max": 6,
  "count": 3,
  "seed": "example"
}

Four decimals between 0 and 1

{
  "min": 0,
  "max": 1,
  "count": 4,
  "integer": false,
  "decimals": 4,
  "seed": "example"
}

Limitations

Uniform, not “random enough”

A naive `random() % n` skews the result toward small numbers whenever n does not divide the generator's range. This tool uses rejection sampling so every value in the range is equally likely.

For unique draws it shuffles range indices rather than retrying collisions, which stays fast and exact even for a small range and a large count.