Why Switch from UUID to ULID? Exploring Benefits and Features

ULID Features

128‑bit compatibility with UUID

1.21 × 10²⁴ unique values per millisecond

Lexicographically sortable (alphabetical order)

Encoded as 26 characters instead of UUID’s 36

Uses Crockford’s Base32 for efficiency and readability (5 bits per character)

Case‑insensitive and URL‑safe (no special characters)

Monotonic ordering that correctly handles identical timestamps

Timestamp

UNIX time in milliseconds

Space sufficient until year 10889

48‑bit integer component

The leftmost characters represent the most significant part, ensuring lexical order; the rightmost characters are the least significant. Within the same millisecond, ordering cannot be guaranteed.

Encoding

ULID uses Crockford’s Base32 alphabet, which excludes I, L, O, and U to avoid confusion and misuse.

Binary Layout and Byte Order

Components are encoded as 16 octets, each in network byte order (most‑significant byte first).

Randomness

80 bits of randomness

Cryptographically strong techniques are used to ensure randomness

Use Cases

Replace UUID in distributed environments for globally unique, millisecond‑precision ordered IDs

Embed timestamps for sharding or partitioning databases by date

When millisecond precision is acceptable, ULID ordering can be used

Serve as a drop‑in replacement for auto‑increment primary keys to reduce database key generation dependency

The article concludes with an invitation for discussion.