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Uuid Generator

UUIDs (Universally Unique Identifiers) are 128-bit identifiers designed to be globally unique without central coordination. Version 4 UUIDs use random bits and are the most common; Version 7 (2022) adds a timestamp prefix for database-friendly sorting. Our generator produces RFC 4122 compliant UUIDs in bulk with format options.

Generated UUIDs

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information.

UUID v4 is randomly generated and has virtually no chance of collision.

Format: 8-4-4-4-12 hexadecimal characters

Example: 550e8400-e29b-41d4-a716-446655440000

Uses: databases, APIs, microservices, distributed systems

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About the UUID Generator

UUIDs (Universally Unique Identifiers) are 128-bit identifiers designed to be globally unique without central coordination. Version 4 UUIDs use random bits and are the most common; Version 7 (2022) adds a timestamp prefix for database-friendly sorting. Our generator produces RFC 4122 compliant UUIDs in bulk with format options.

How to use it

  1. Click Generate for one UUID v4 (random).
  2. Set quantity to generate up to 1,000 UUIDs at once.
  3. Choose version: v1 (time-based), v4 (random), v5 (namespace+name SHA-1), v7 (time-ordered).
  4. Select format: standard (8-4-4-4-12), no hyphens, uppercase, or braces.

Formula & methodology

UUID v4: 128 random bits with version (4) and variant (10) bits set. Format: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where y ∈ {8,9,a,b}. Total unique v4 UUIDs: 2^122 ≈ 5.3 × 10^36. Birthday attack collision at 50% probability: after 2.71 × 10^18 UUIDs generated. In practice: collision probability is negligible for any realistic system.

Common use cases

  • Database primary keys: UUID vs auto-increment for distributed systems
  • API identifiers: resource IDs that don't reveal record count
  • Session tokens: UUID v4 for unpredictable session IDs
  • File naming: generated filenames for uploaded user content
  • Distributed systems: UUID v7 for time-ordered keys in Cassandra, DynamoDB

Frequently asked questions

Auto-increment: simpler, smaller (4–8 bytes vs 16), better index performance, easier debugging. UUID: works across distributed systems without coordination, doesn't expose record counts, safe to expose in URLs. UUID v7 (time-ordered) solves the index fragmentation problem of v4 by keeping inserts sequential. Rule of thumb: use auto-increment for single-database apps; use UUID v7 for distributed systems or public-facing IDs.
In practice, yes. With 2^122 possible values, you'd need to generate 1 billion UUIDs per second for 86 years to have a 50% chance of one collision. Real-world UUID generators use cryptographically secure random number generators (CSPRNG), making accidental collision essentially impossible. The larger concern is using weak random number generators (Math.random() in JS) — always use crypto.randomUUID() or equivalent.

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