How to Generate UUID Online — Free UUID v4 & v7 Generator

What a UUID is

A UUID (Universally Unique Identifier) is a 128-bit number that's effectively guaranteed not to collide with any other UUID ever generated, anywhere. That makes UUIDs a drop-in replacement for database auto-increment IDs when you need to generate IDs on the client, merge datasets from different systems, or expose IDs in URLs without leaking count information. The UUID generator produces RFC 4122 UUIDs in multiple versions.

The versions, and when to use each

Version	Source	Sortable?	Use when
v1	Time + MAC address	Yes (barely)	Rare; legacy systems only — leaks MAC
v4	Cryptographic randomness	No	Default choice — anything where ID must be unpredictable
v7	Timestamp + randomness	Yes	Modern default for DB keys; preserves insert order

Why v7 matters for databases

v4 UUIDs are random, which is great for security but terrible for database index locality. Inserting v4 keys into a B-tree hits random pages — write amplification goes up, cache hit rate goes down. v7 UUIDs embed a millisecond timestamp as the high bits, so inserts append to the tip of the index instead of scattering. Same size, same uniqueness guarantees, dramatically better DB performance.

Collision probability (spoiler: you'll never hit it)

For v4 UUIDs to hit even a 50% chance of one collision, you'd need to generate about 2.71 quintillion of them. That's 1 billion UUIDs per second for 85 years. You can safely treat collisions as impossible for any realistic workload.

Formatting quirks

• Standard form: xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx (hyphens required by RFC)
• Compact form: no hyphens — saves 4 bytes but breaks RFC-aware parsers
• Braces: {xxxxxxxx-...-xxxxxxxxxxxx} — Microsoft GUID convention, same 128-bit value
• Base64-encoded UUID: 22 characters instead of 36 — useful in URLs where size matters

Bulk generation

Need 10,000 UUIDs for seeding a test database? The generator does batch output in one click. Every UUID uses crypto.getRandomValues(), so the batch is as random as a single draw — no weaker PRNG when you ask for more.

Related generators

For non-UUID random strings with custom alphabets (useful for short URL slugs), use the random string generator. For secure passwords, the password generator uses the same crypto source but produces human-typeable output. For one-way hashes (when you need a deterministic ID from input), use the hash generator.