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UUID Generator

Generate random UUID v4 identifiers for databases, APIs, and distributed systems.

UUID Generator

Generate random UUID v4 identifiers for your projects.

What Is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit value used to uniquely identify information in computer systems. Also known as a GUID (Globally Unique Identifier) in Microsoft ecosystems, UUIDs are formatted as 32 hexadecimal digits displayed in five groups separated by hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.

UUID Versions

There are several UUID versions, each with a different generation method:

  • Version 1: Based on the current timestamp and the MAC address of the computer. Guarantees uniqueness but reveals hardware and time information.
  • Version 3: Generated by hashing a namespace and name with MD5. Deterministic: the same input always produces the same UUID.
  • Version 4: Generated from random or pseudo-random numbers. This is the most commonly used version and what this tool generates. The probability of collision is astronomically low (about 1 in 5.3 x 10^36 for the first collision after generating 103 trillion UUIDs).
  • Version 5: Like version 3 but uses SHA-1 instead of MD5. Preferred over v3 for new applications.
  • Version 7: A newer format (RFC 9562) that combines a Unix timestamp with random data, making UUIDs sortable by creation time while maintaining uniqueness.

Common Use Cases for UUIDs

  • Database primary keys: UUIDs allow generating unique IDs without coordinating with a central database, essential for distributed systems.
  • API request tracking: Assign a UUID to each API request for logging and debugging across microservices.
  • Session identifiers: Web applications use UUIDs to track user sessions securely.
  • File naming: Prevent filename collisions when multiple users upload files simultaneously.
  • Message queues: Ensure each message has a unique identifier for deduplication and tracking.

UUIDs vs. Auto-Increment IDs

Traditional auto-incrementing integer IDs (1, 2, 3...) are simple and compact, but they have limitations. They require a single authority to assign the next number, which creates a bottleneck in distributed systems. They also leak information: if your user ID is 1547, an attacker knows there are at least 1,547 users and can enumerate other records. UUIDs solve both problems at the cost of being larger (128 bits vs. 32-64 bits) and less human-readable.

Frequently Asked Questions

Are UUID v4 values truly unique?
While not mathematically guaranteed to be unique, UUID v4 values are unique for all practical purposes. With 122 random bits, there are 5.3 x 10^36 possible values. The probability of generating a duplicate after creating 1 billion UUIDs is about 0.00000000000000005%. You would need to generate 103 trillion UUIDs to have a 50% chance of a single collision.
How can I identify a UUID version?
The version number is encoded in the UUID itself. Look at the first digit of the third group (after the second hyphen). For example, in "550e8400-e29b-41d4-a716-446655440000", the "4" at position 13 indicates this is a version 4 UUID. Similarly, version 1 UUIDs have a "1" in that position, version 7 has a "7", and so on.
Should I use UUIDs or auto-increment IDs for my database?
It depends on your needs. Use auto-increment IDs when you have a single database server, need compact storage, or want human-readable references. Use UUIDs when building distributed systems, merging data from multiple sources, generating IDs client-side, or when you need to prevent enumeration attacks. Many modern applications use UUIDv7 as a compromise since it is sortable like auto-increment but globally unique like UUIDs.
Are UUIDs generated in the browser secure?
This tool uses crypto.randomUUID() when available, which relies on the Web Crypto API and a cryptographically secure random number generator. This is suitable for most applications. However, for high-security use cases like cryptographic key generation or authentication tokens, generate UUIDs server-side using a well-audited library.

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