UUID Generator

Generate random UUID v4 strings instantly. Bulk generate unique identifiers for databases, APIs, and testing. Free online UUID/GUID generator.

Last updated: June 1, 2026

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What is UUID Generator?

A UUID (Universally Unique Identifier) is a 128-bit identifier that is guaranteed to be unique across all devices and all time without requiring a central authority. UUID v4 specifically uses cryptographically strong random numbers to generate identifiers in the format xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where x is a random hex digit and y is one of 8, 9, a, or b. UUIDs are the standard way to create unique identifiers in distributed systems, databases, APIs, and software applications. With 2^122 possible values (over 5 undecillion combinations), the probability of generating a duplicate is astronomically small — you'd need to generate 1 billion UUIDs per second for 85 years to have a 50% chance of a single collision.

How It Works

This tool uses the Web Crypto API (crypto.randomUUID() or crypto.getRandomValues()) to generate cryptographically secure random numbers. These random bytes are formatted into the standard UUID v4 format: 8-4-4-4-12 hex characters separated by hyphens. The '4' in the third group indicates this is a version 4 (random) UUID. You can generate a single UUID or bulk generate up to 1000 at once. All generation happens locally in your browser using your operating system's secure random number generator — no network requests are made.

Examples

Single UUID v4 generation

Input

Generate 1 UUID

Output

f47ac10b-58cc-4372-a567-0e02b2c3d479

Tips & Best Practices

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UUID v4 has 122 bits of randomness. You'd need to generate 2.71 quintillion UUIDs to have a 50% chance of one collision.

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For database performance, consider UUID v7 (time-ordered) over v4 (random). Random UUIDs cause B-tree index fragmentation.

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UUIDs are 128 bits (16 bytes). If storage is critical, consider using the binary format instead of the 36-character string representation.

Common Use Cases

•Creating primary keys for database records in PostgreSQL, MongoDB, or DynamoDB
•Generating unique identifiers for API resources and endpoints in REST/GraphQL APIs
•Assigning unique session IDs and correlation IDs for request tracing in microservices
•Creating unique filenames for uploaded files to prevent collisions in cloud storage
•Generating idempotency keys for payment processing and financial transactions
•Assigning unique identifiers to test fixtures, mock data, and automated test cases

Frequently Asked Questions

What is a UUID?▼

A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information. UUID v4 uses cryptographically strong random numbers to generate identifiers that are statistically guaranteed to be unique without any coordination between systems.

Can I generate multiple UUIDs at once?▼

Yes, you can generate up to 1000 UUIDs in bulk with a single click. All are generated using cryptographically secure random numbers and can be copied together.

Are generated UUIDs truly unique?▼

UUID v4 uses cryptographically strong random numbers with 122 bits of randomness. The probability of collision is approximately 1 in 2^61 after generating 1 billion UUIDs — effectively impossible in any practical application.

What's the difference between UUID and GUID?▼

They're the same thing. UUID is the standard term used in RFC 4122 and most programming languages. GUID (Globally Unique Identifier) is Microsoft's name for the same concept, used in .NET and Windows APIs.

Should I use UUIDs as database primary keys?▼

UUIDs work well as primary keys in distributed systems where auto-increment isn't practical. The trade-off is slightly larger storage (16 bytes vs 4-8 for integers) and potential index fragmentation. Many databases like PostgreSQL have native UUID types that handle this efficiently.

Are UUIDs sequential or random?▼

UUID v4 is fully random. If you need time-ordered UUIDs (for better database index performance), consider UUID v7 which embeds a timestamp while maintaining uniqueness. This tool generates v4 (random) UUIDs.