v1 — Based on timestamp + MAC address (node). Includes time, clock sequence, and node fields.
v4 — Randomly generated. 122 bits of randomness. Most commonly used.
v7 — Unix timestamp (ms) + random. Sortable by creation time. Modern replacement for v1.
ULID — 128-bit ID. 48-bit timestamp + 80-bit random. Crockford Base32 encoded. Lexicographically sortable.
Nano ID — URL-friendly unique string (A-Za-z0-9_-). Configurable length, default 21 chars.