Blog · 2026-03-16

UUIDs vs ULIDs: randomness, sortability, and database indexes

Pick identifiers that match your storage engine and observability needs — random v4 blobs fragment indexes differently than time-ordered strings.

uuididentitydatabases

Lexicographic time ordering

ULIDs embed a timestamp prefix, which helps humans scan logs chronologically when IDs appear as plain text. UUIDv7 offers similar benefits with standard formatting.

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Generate identifiers with vetted libraries in production. Online generators are ideal for mock data, load tests, and UI scaffolding.

Try these tools next

  • UUID Generator — Generate RFC-4122 v4 UUIDs instantly.
  • ULID Generator — Client-side ulid generator — runs locally in your browser for speed and privacy.
  • NanoID Generator — Client-side nanoid generator — runs locally in your browser for speed and privacy.

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