UUID v4 Generator
Generate cryptographically random universally unique identifiers
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UUID v4
Random UUIDs. Most commonly used for general purposes.
UUID v7
Time-ordered and random. Best for databases and sorting.
ULID
Sortable 26-char IDs. Perfect for distributed systems.
NanoID
Compact 21-char URL-safe IDs. Great for frontend use.
550e8400-e29b-41d4-a716-446655440000What is UUID v4?
UUID v4 is the most widely used UUID version, generating identifiers using random or pseudo-random numbers. Each UUID v4 has 122 random bits, making collisions practically impossible—you'd need to generate 1 billion UUIDs per second for 85 years to have a 50% chance of collision.
The "4" in UUID v4 indicates version 4, which appears in the 13th character of the UUID. The format follows the standard 8-4-4-4-12 pattern: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where y is one of 8, 9, a, or b.
Why Use UUID v4?
UUID v4 is the default choice for most applications because it requires no coordination or central authority. Any system can generate UUIDs independently without risk of collision. This makes v4 perfect for distributed systems, microservices, and offline-capable applications.
Unlike auto-incrementing integers, UUID v4 reveals no information about creation order or count. This provides security through obscurity—attackers can't enumerate IDs or predict next values.
How UUID v4 Works
UUID v4 generation follows RFC 4122:
1. Generate 128 random bits 2. Set version bits (4) at position 12-15 of time_hi_and_version 3. Set variant bits (10) at position 6-7 of clock_seq_hi_and_reserved 4. Format as 32 hex digits with hyphens
Modern implementations use cryptographically secure random number generators (CSPRNG) to ensure unpredictability.
Common Use Cases
- Database primary keys
- API resource identifiers
- Session tokens and correlation IDs
- Distributed systems without coordination
Pro Tip
Store UUIDs as binary(16) in databases for better performance and smaller storage compared to varchar(36).
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