UUID Generator

About this tool

A UUID — Universally Unique Identifier — is a 128-bit value formatted as 32 hexadecimal digits split into five groups, like 3f2504e0-4f89-11d3-9a0c-0305e82c3301. The point of a UUID is right there in the name: it is designed so that two independently generated UUIDs, created on different machines with no coordination between them, are astronomically unlikely to collide. That property is what makes UUIDs useful as primary keys, request IDs, session identifiers, and file names across distributed systems — you can generate an ID locally, with no round trip to a central authority to check it's unique, and trust that it will be.

This generator supports the two UUID versions developers actually reach for. Version 4 is the one you'll use for almost everything: it's built from 122 random bits (the remaining 6 bits encode the version and variant), generated using your browser's cryptographically secure random number source. There's no information encoded in a v4 UUID beyond its own bits — it reveals nothing about when or where it was created, which is exactly the point when you want an opaque, unguessable identifier for a database row, an API resource, or a tracking token. Version 1 takes a different approach: it encodes the current timestamp (to 100-nanosecond precision) and a node identifier into the UUID itself, which means v1 UUIDs are sortable by creation time and — historically — traceable back to the generating machine's MAC address. This tool generates the node identifier randomly rather than using your actual hardware address, which is the modern, privacy-conscious approach recommended when a real MAC address isn't required.

The practical difference in choosing between them: reach for v4 by default, since it's simpler, carries no metadata, and is what most frameworks and databases expect when they say "UUID." Reach for v1 specifically when you want IDs that sort roughly in creation order — useful for some database indexing strategies where monotonically-increasing keys reduce write amplification, or for debugging scenarios where being able to eyeball an approximate creation time from the ID itself is genuinely useful.

Bulk generation exists because the single-UUID case is rarely the real use case in development — seeding a test database with a thousand fake user IDs, generating placeholder keys for a migration script, or producing a batch of unique tokens for a load test are all one-off tasks that are tedious to script by hand for a quick check. Generate up to a thousand at once, then copy the whole list or download it as a plain text file, one UUID per line.