Developer

UUID Generator — Free 2026

Generate cryptographically random UUID v4 values in bulk. Choose your format and copy instantly.

Quantity Enter a number between 1 and 500.

Format

Generated UUIDs

How It Works

Set the quantity
Choose a format
Generate and copy

Understanding UUIDs

A Universally Unique Identifier (UUID) is a 128-bit label used to uniquely identify resources in computing systems. Standardized by RFC 4122, UUIDs are designed to be globally unique without requiring a central registration authority. This makes them ideal for distributed systems where multiple nodes need to create identifiers independently without risk of collision. The standard UUID format is 32 hexadecimal characters arranged in five groups separated by hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.

There are five official UUID versions, each using a different generation strategy. Version 1 uses the host's MAC address and current timestamp. Version 3 and version 5 generate deterministic UUIDs from a namespace and a name using MD5 and SHA-1 hashing respectively. Version 4, which this tool generates, uses random or pseudo-random numbers for all bits except the version and variant markers. Version 4 is by far the most commonly used in modern software development because it is simple, does not leak hardware information, and has an astronomically low collision probability.

UUID v4 and Cryptographic Randomness

This tool uses the browser's native crypto.randomUUID() method when available, which generates UUIDs using a cryptographically secure random number generator. In browsers that do not support this method, it falls back to crypto.getRandomValues() to fill random bytes and manually applies the version 4 and variant bits. Either way, the UUIDs produced are suitable for security-sensitive applications where predictability would be a vulnerability.

With 122 random bits, UUID v4 provides approximately 5.3 × 10³⁶ possible values. To put this in perspective, you could generate one billion UUIDs per second for 100 years and the probability of a single duplicate would still be vanishingly small. This is why UUIDs are trusted as primary keys in databases, distributed message queues, session identifiers, and file naming systems across the technology industry.

Choosing the Right Format

The standard UUID format with hyphens (550e8400-e29b-41d4-a716-446655440000) is the most recognizable and is required by most database UUID column types. The no-dash format removes hyphens for contexts where hyphens are inconvenient, such as file names or URL parameters. Uppercase formatting is sometimes required by legacy systems or specific API specifications. For other developer tools, check out our JSON formatter for prettifying API responses, or our regex tester for validating UUID patterns in your code.

Frequently Asked Questions

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit value used to uniquely identify information in computer systems. The standard format is 32 hexadecimal digits displayed in five groups separated by hyphens: 8-4-4-4-12. UUIDs are designed to be unique across all systems without a central authority.

What is UUID version 4?

UUID v4 is generated using random or pseudo-random numbers. Of the 128 bits, 6 are fixed (4 bits for version and 2 bits for variant), leaving 122 random bits. This gives approximately 5.3 x 10^36 possible UUIDs, making collisions virtually impossible. This tool uses crypto.randomUUID() for cryptographically secure generation.

Can two UUIDs ever be the same?

While theoretically possible, the probability of generating two identical UUID v4 values is astronomically small — about 1 in 2^122 (approximately 5.3 x 10^36). You would need to generate about 2.71 quintillion UUIDs to have a 50% chance of a single collision. In practice, UUID collisions are not a concern.

When should I use UUIDs instead of auto-increment IDs?

UUIDs are preferred when you need IDs generated on the client side, in distributed systems without a central database, when merging data from multiple sources, or when sequential IDs would expose business information (like order volume). Auto-increment IDs are simpler and more storage-efficient for single-database applications.