Are these UUIDs truly random?

Yes. They use the browser's window.crypto.getRandomValues() API, which provides cryptographically secure random numbers — the same source used for TLS and encryption.

Can I generate thousands of UUIDs at once?

Yes! The generator handles large batches efficiently without blocking the browser. A loading indicator appears for very large counts.

UUID v4 is a version of UUID that is generated using 122 bits of cryptographically secure random data. It has the format xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where '4' indicates the version and 'y' is one of 8, 9, a, or b.

Will I ever get a duplicate UUID?

It is statistically virtually impossible. The probability of a collision is approximately 1 in 5.3 × 10^36 — you could generate a billion UUIDs per second for 100 years and the chance of a single duplicate would still be vanishingly small.

UUID v4 Generator

Generate standard cryptographically secure random UUIDs instantly in bulk.

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Need unique identifiers for database records, API keys, or distributed systems? Generate single or bulk UUID v4 identifiers using the browser's cryptographic random number generator — no patterns, no collisions.

Last Updated: April 28, 2025Privacy: 100% Local Browser Processing

What is the Uuid?

A UUID (Universally Unique Identifier) Generator creates random 128-bit identifiers in the standard version 4 format (xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx). UUID v4 uses cryptographically secure random numbers to ensure statistical uniqueness — the probability of generating a duplicate is so low (1 in 2^122) that it is effectively impossible even across billions of generations. UUIDs are used as database primary keys, session tokens, tracking identifiers, and unique resource names in distributed systems.

Pro Tips & Best Practices

UUIDs are designed for uniqueness, not secrecy. If you need an unguessable token (like an API key), combine a UUID with additional entropy or use a dedicated secret generation tool.
In PostgreSQL, use the 'uuid' column type instead of storing UUIDs as strings — it uses 16 bytes instead of 36 characters and supports indexing optimized for UUID comparisons.
If you need ordered/sortable UUIDs for database performance, consider UUID v7 (time-ordered) instead of v4. This tool generates v4 (fully random).
When generating UUIDs in bulk, download the result as a text file rather than copying — clipboard operations can be slow for very large lists.

Technical Deep Dive

UUID v4 generates identifiers using 122 bits of random data (the remaining 6 bits encode the version and variant). The '4' in the third group indicates version 4, and the first character of the fourth group (8, 9, a, or b) indicates the RFC 4122 variant. This tool uses the Web Crypto API's crypto.getRandomValues() method to generate the random bytes — this is the same cryptographic random number generator used for TLS key generation, ensuring that the UUIDs are not predictable or guessable. This is a critical distinction from Math.random()-based implementations, which use a pseudo-random number generator that can be seeded and predicted. For bulk generation, the tool generates UUIDs in batches using requestAnimationFrame to prevent blocking the browser's main thread, ensuring the UI remains responsive even when generating thousands of UUIDs. The output can be copied as a newline-separated list or downloaded as a text file for import into databases, configuration files, or seeding scripts.

How to Use

1Click Generate to create a single UUID v4.
2Set a count to generate UUIDs in bulk (up to thousands).
3Click Copy All to copy the entire list to your clipboard.
4Download the list as a text file for batch processing.
5Each UUID uses window.crypto for cryptographic security.

Real-World Use Cases

Database primary keys — use UUIDs as primary keys in PostgreSQL, MySQL, or MongoDB to enable distributed ID generation without a central sequence.
Session management — generate unique session tokens for authentication systems where sequential IDs would be a security risk.
File naming — create unique filenames for uploads to S3, GCS, or local storage to prevent collisions without maintaining a name registry.
Distributed systems — generate unique identifiers across multiple microservices without coordination, enabling eventual consistency architectures.