What are UUIDs and ULIDs?
UUIDs (Universally Unique Identifiers) and ULIDs (Universally Unique Lexicographically Sortable Identifiers) are both 128-bit identifiers used to uniquely identify information in computer systems. While UUIDs have been the industry standard for decades, ULIDs offer additional benefits like time-based sorting and a more compact representation.
When to Use UUID
UUIDs are ideal when you need widely recognized, standardized identifiers. They're perfect for distributed systems where coordination isn't possible, database primary keys, API resources, and session tokens. UUID v4 uses random numbers, making them unpredictable and suitable for security-sensitive applications.
When to Use ULID
ULIDs are excellent when you need time-ordered identifiers. They're perfect for event sourcing, message queues, log entries, and any system where chronological ordering matters. The sortable nature of ULIDs makes them more efficient for database indexing compared to random UUIDs.
Key Differences
The main difference is sortability: UUIDs are random and don't sort meaningfully, while ULIDs sort chronologically. ULIDs also use a more URL-friendly character set (Crockford's Base32) and are slightly shorter (26 vs 36 characters). Both provide the same level of uniqueness and can be used interchangeably in most applications.