UUID vs CUID vs NanoID: Choosing an ID Generator

Comparing ID Generation Strategies

Choosing the right ID format affects database performance, URL readability, and system scalability. Each approach makes different trade-offs between uniqueness guarantees, sortability, and string length.

UUID v4

UUID v4 generates 128-bit random identifiers formatted as 36-character strings (e.g., 550e8400-e29b-41d4-a716-446655440000). They're universally supported and virtually guaranteed unique, but they're long, not sortable by creation time, and can cause B-tree index fragmentation in databases due to random ordering.

UUID v7 and ULID

UUID v7 (RFC 9562) and ULID both embed a timestamp prefix, making them naturally sortable by creation time. This dramatically improves database insert performance since new records always append to the end of B-tree indexes. ULID uses Crockford Base32 encoding, producing 26-character strings that are URL-safe and case-insensitive.

NanoID and CUID2

NanoID generates compact 21-character IDs using a customizable alphabet. CUID2 produces collision-resistant IDs optimized for horizontal scaling. Both are shorter than UUIDs, making them better for URLs and client-side storage. NanoID is particularly popular in frontend applications where bundle size matters — the library is only 130 bytes.

Selection Guide

Use UUID v7 or ULID for database primary keys where sort order matters. Choose NanoID for URL slugs and client-facing identifiers where brevity is valued. Stick with UUID v4 when you need maximum interoperability with existing systems. Avoid sequential integers for public-facing IDs, as they leak information about your system's scale and growth rate.