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uuid 2025-01-18

UUID vs ULID: Understanding the Differences

Compare UUID and ULID to choose the right identifier for your application.

Unique identifiers are essential in distributed systems. Let's compare UUID and ULID.

What is UUID?

UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 4122.

UUID Versions:

  • v1: Based on timestamp and MAC address
  • v4: Random (most commonly used)
  • v7: Time-ordered with random component (newest)

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

What is ULID?

ULID (Universally Unique Lexicographically Sortable Identifier) is a 128-bit identifier that is:

  • Lexicographically sortable
  • Canonically encoded as 26 characters
  • Uses Crockford's Base32

Example: 01ARZ3NDEKTSV4RRFFQ69G5FAV

Key Differences

FeatureUUID v4ULID

|---------|---------|------|

SortableNoYes Length36 chars26 chars Character setHex + dashesCrockford Base32 Time componentNoYes (48-bit)

When to Use Each

Use UUID when:

  • You need RFC compliance
  • Compatibility with existing systems
  • No sorting requirement

Use ULID when:

  • You need chronological sorting
  • Database index performance matters
  • You want shorter IDs

Database Considerations

ULIDs improve database performance because:

  • Sequential inserts are faster
  • Better index locality
  • Reduced page splits in B-trees

Use our UUID Generator to create UUIDs of any version.