Random Number Generator: Generate Secure Random Numbers with Custom Options

Whether you need a random number for a lottery draw, a simulation, a classroom exercise, or a security token, the quality of randomness matters. Our Random Number Generator uses the Web Crypto API for cryptographically secure results and gives you full control over range, quantity, decimal precision, and uniqueness constraints.

How to Use Our Random Number Generator

1. Set the minimum and maximum — define the range for your random numbers
2. Set the count — how many random numbers to generate at once
3. Choose decimal places — generate integers (0 decimals) or numbers with up to several decimal places
4. Toggle unique mode — ensure no duplicates when generating multiple numbers
5. Click Generate and copy the results

Features Explained

Range Control

Set any minimum and maximum value. The generator works with both positive and negative numbers, so you can generate values from -1000 to 1000 or from 1 to 6 to simulate a dice roll.

Count

Generate anywhere from a single number to a large batch. This is useful when you need a set of random values for testing, sampling, or simulations rather than generating them one at a time.

Decimal Precision

• 0 decimals — whole integers like 7, 42, or 256
• 1 decimal — values like 3.8 or 12.4
• 2 decimals — values like 0.73 or 99.15
• More precision — for scientific or statistical applications where fine-grained values are needed

Unique Mode

When unique mode is on, no two numbers in the generated set will be the same. This is essential for:

• Lottery or raffle draws where repeats are not allowed
• Sampling without replacement
• Assigning unique IDs or positions
• Shuffling a sequence of numbers

Note: unique mode requires that the range is large enough to accommodate the requested count. You cannot generate 100 unique integers from a range of 1 to 50.

Security: Web Crypto API

Our generator uses crypto.getRandomValues(), the same cryptographically secure random number generator built into modern browsers. This is the randomness source behind TLS key generation, password managers, and cryptographic libraries.

Unlike Math.random(), which uses a pseudo-random algorithm that can be predicted if the seed is known, the Web Crypto API draws from the operating system’s entropy pool. The results are suitable for security-sensitive applications.

Common Use Cases

Use Case	Suggested Config
Dice roll (D6)	Range 1-6, count 1, 0 decimals
Lottery draw (6 of 49)	Range 1-49, count 6, 0 decimals, unique
Coin flip	Range 0-1, count 1, 0 decimals
Random percentage	Range 0-100, count 1, 2 decimals
Test data IDs	Range 1000-9999, count 20, 0 decimals, unique
Monte Carlo sample	Range 0-1, count 1000, 6 decimals
Random RGB value	Range 0-255, count 3, 0 decimals
Temperature simulation	Range -20 to 45, count 30, 1 decimal

Tips

• For a fair coin flip, use range 0-1 with 0 decimals. Map 0 to heads and 1 to tails.
• To simulate rolling multiple dice (like 2d6 in tabletop games), generate 2 numbers in the range 1-6 and add them together.
• When generating test data, use unique mode to avoid accidentally creating duplicate IDs that could cause primary key conflicts in a database.
• For statistical simulations, higher decimal precision (4-6 places) gives you finer granularity in your distributions.
• All generation happens in your browser. No numbers are sent to a server, so your results remain private.

Frequently Asked Questions

Are these numbers truly random? Yes. They use cryptographic randomness from your browser’s Web Crypto API, which draws from your operating system’s entropy pool. The output is unpredictable and suitable for security-sensitive applications.

Can I generate negative numbers? Yes. Set the minimum to a negative value. For example, a range from -50 to 50 will produce numbers anywhere in that span.

What happens if I request more unique numbers than the range allows? The generator will let you know that the range is too small. For example, you cannot generate 20 unique integers from a range of 1 to 10.

Does this work offline? Yes. Everything runs in your browser using the Web Crypto API. No network requests are made, and your generated numbers are never transmitted anywhere.

What is the difference between this and Math.random()? Math.random() is a pseudo-random number generator (PRNG) that uses an algorithm seeded internally. It is predictable if the seed state is known and is not suitable for security-sensitive tasks. The Web Crypto API provides true cryptographic randomness from hardware entropy sources.

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Try our free Random Number Generator to generate secure random numbers instantly.