Random Number Generator

Generate cryptographically secure random numbers with ThisDevTool's Random Number Generator.

Last reviewed: April 2026
Reviewed by , software engineer Β· last updated April 2026

New to this tool? Click here for instructions

Click Generate to create random numbers.
Configure options and click Generate.

How to Use the Random Number Generator

To use the Random Number Generator, follow these steps:

1. Choose a mode: Numbers, Dice Roller, Coin Flipper, or Lottery Picker.

2. Configure the settings: set your range, count, decimals, and unique options.

3. Click Generate (or Roll/Flip/Pick for the specialized modes).

4. View, copy, or download the results.

  • Numbers: Generate random numbers in any range with any number of decimal places.
  • Dice Roller: Roll up to 20 dice simultaneously using cryptographic randomness.
  • Coin Flipper: Flip a fair coin one to 100 times and see the distribution.
  • Lottery Picker: Pick a set of unique numbers from any range.

When to Use the Tool in Real Workflows

Use the Random Number Generator when you need cryptographically secure random numbers for various purposes, including:

1. Games and simulations where true randomness is crucial.

2. Security-sensitive tasks like generating secure passwords or tokens.

3. Statistical analysis and probability demonstrations.

4. Creating randomized test datasets or sampling without replacement.

How It Works

The Random Number Generator uses the Web Crypto API's crypto.getRandomValues() method to generate cryptographically secure random numbers. This method draws entropy from your operating system's cryptographically secure random source, ensuring that the numbers produced are statistically indistinguishable from true randomness. Unlike Math.random(), which is a pseudo-random number generator (PRNG), crypto.getRandomValues() is designed to be secure and suitable for use in security-sensitive contexts.

Tips, Edge Cases, or Limitations

1. Security: Always use the Random Number Generator for security-sensitive tasks as it provides cryptographically secure random numbers.

2. Range and Count: Be mindful of the range and count settings to avoid generating too many numbers, which could lead to performance issues.

3. Unique Numbers: Enable the Unique mode when you need to ensure no number appears twice, which is useful for drawing lots or creating randomized test datasets.

4. Browser Compatibility: The Random Number Generator works in all modern browsers, including Chrome, Firefox, Safari, and Edge.

5. Offline Use: The tool requires an internet connection to function as it relies on external services for code beautification and other features.

Frequently Asked Questions

Yes, the Random Number Generator uses the Web Crypto API's crypto.getRandomValues() method, which draws entropy from your operating system's cryptographically secure random source. This ensures that the numbers produced are statistically indistinguishable from true randomness.
Unique mode ensures that no number appears twice, making it suitable for drawing lots, sampling without replacement, or creating randomized test datasets. Non-unique mode allows for repeated numbers.
The dice roller supports all standard tabletop RPG dice (d4, d6, d8, d10, d12, and d20) and rolls up to 20 dice simultaneously. Each roll is independent and uses cryptographic randomness, making the results far more unpredictable than physical dice.
The lottery picker allows you to pick a set of unique numbers from any range. It ensures that numbers are always unique (no repeats) and drawn without replacement, mimicking a real lottery machine.
The histogram shows the distribution of the generated numbers, making it easy to verify uniformity across your range. This is particularly useful for statistical analysis and probability demonstrations.

Quick reference

Random Number Generator Parameters
Range Distribution Seed Example
1-100 Uniform 42 73
1-1000 Normal 1337 543
0-1 Uniform 999 0.34
1-1000000 Poisson 7 421
0-100 Uniform 12345 87
1-10 Exponential 666 3