UUID & ID Generator

Which ID should I use?

• UUID v4 is the safe default: 122 random bits, supported everywhere. Its only downside is that random keys scatter writes across a database index.
• UUID v7 (RFC 9562) puts a millisecond timestamp first, so new IDs sort after old ones. Use it for primary keys in Postgres, MySQL or SQLite when you want UUIDs that are also roughly chronological.
• ULID is the same idea as v7 in a shorter, case-insensitive, 26-character form. It converts losslessly to and from a UUID.
• UUID v5 and v3 are deterministic: hash a namespace and a name and you get the same UUID every time. Handy for idempotency keys or mapping external IDs.
• NanoID is for short IDs in URLs. Pick the alphabet and length and the tool tells you how many bits of entropy that gives.
• Random tokens are plain random bytes for API keys, session secrets and salts. 32 bytes (256 bits) is plenty.

Everything is generated with the browser's cryptographic random number generator and never leaves your machine. IDs created in the same millisecond are kept strictly increasing for UUID v7 and ULID.