UUID Generator

A UUID is a 128-bit identifier written as 32 hex digits in the familiar 8-4-4-4-12 pattern. They're used as database keys, request and trace IDs, idempotency keys, and filenames — anywhere you need a value that's unique without a central authority handing out numbers. This tool generates them locally with your browser's cryptographic random source.

Which version should you pick?

The version changes how the bits are filled, and it's a real decision, not cosmetic:

• v4 — random. 122 of the 128 bits are random, the rest fixed by the spec. The odds of a collision are astronomically low, so v4 is the safe default whenever you just need a unique value and don't care about ordering.
• v7 — time-ordered. The high bits hold a 48-bit Unix millisecond timestamp, with the rest random. That means v7 IDs sort by creation time. As a database primary key this is a big win over v4: sequential-ish keys keep new rows landing at the end of the B-tree index instead of scattering random inserts across it, which reduces page splits and index fragmentation. Reach for v7 for new primary keys.
• v1 — timestamp + node. The classic time-based UUID: a 100-nanosecond timestamp plus a clock sequence and a node ID. Be aware it embeds the creation time in the value, which can leak when a record was made.

Formatting for whatever consumes it

Three toggles reshape the output, and they combine:

• Uppercase — A1B2… instead of a1b2…; some legacy systems expect it.
• No hyphens — the bare 32-character form, handy for URLs, filenames, or compact columns.
• Braces — wraps each in {…}, the form Microsoft/COM GUIDs use in registry entries and C# code.

The hyphens are purely presentational — the same 128-bit value with or without them — so strip or keep them to match the field you're pasting into.

Bulk generation

Set the count to make up to 500 at once. Copy all grabs the whole list (one per line) for seeding a table, a fixture file, or a test data set; each row also has its own copy button for grabbing a single value.

Things worth knowing

• Every UUID uses crypto.getRandomValues, the browser's cryptographically strong random source — not the weaker Math.random — so the values are suitable as unpredictable identifiers.
• Generation is entirely on-device; nothing about the request leaves your browser.
• The canonical form is 36 characters (32 hex digits plus 4 hyphens); the no-hyphens toggle gives the compact 32-character version. Both encode the identical value.
• A UUID is an identifier, not a secret. Even a random v4 isn't an authorization token — don't rely on it being unguessable to protect a resource; use a real session token or signed URL for that.
• If you're choosing for a fresh database schema, v7 is usually the best default today; keep v4 for tokens and IDs where you specifically don't want the time embedded or inferable.