UUIDv4 vs ULID: Which ID Format Should You Use?
Choosing the right identifier format impacts database performance, URL readability, and ordering. UUIDv4 is purely random, while ULID includes a timestamp for natural ordering.
Quick comparison
- UUIDv4: Random, widely supported, no natural ordering.
- ULID: Time-ordered, URL-safe, better for sortable indexes.
- Collision risk: Both are extremely low when generated correctly.
When to use UUIDv4
Use UUIDv4 for simplicity, interoperability, and when ordering is not required. It’s a safe default for identifiers in APIs and event tracking.
When ULID is a better fit
ULIDs are lexicographically sortable, which helps with time-series data and ordered indexes. That can speed up database reads for recent records.
Validation and generation tips
Always validate incoming IDs and avoid generating IDs on client devices without proper randomness. For consistent generation, use UUID & ULID Lab to generate and validate IDs in bulk.
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