GUID generator
One click, as many GUIDs as you need — random UUID v4 from your browser's crypto API, with formatting options and bulk copy.
Generating…
Inside a UUID v4
Every GUID on this page is produced by your browser's crypto.randomUUID(), which draws from the operating system's secure random source. The layout is fixed by RFC 4122:
- The 13th hex digit is always 4 — the version marker.
- The 17th hex digit is one of 8, 9, a, b — the variant marker.
- The other 30 digits (122 bits) are pure randomness — that's where the uniqueness comes from.
Because uniqueness comes from randomness rather than a central registry, any machine can mint IDs at any time with no coordination — which is exactly why UUIDs are the default primary key in so many distributed systems.
Which format to pick
- Lowercase with hyphens — the canonical RFC form; use it unless a system demands otherwise. Postgres, most APIs, and JSON schemas expect this.
- Braces — the Windows registry / COM style, {3f2b0c4e-…}, still required by some Microsoft tooling and .reg files.
- No hyphens — a compact 32-character form used in URLs, filenames, and systems that store the id as a plain hex string.
- Comparisons should be case-insensitive, but be consistent: mixing cases across a codebase is a classic source of "identical" IDs that fail an equality check.
Frequently asked questions
What is a GUID?
A GUID (globally unique identifier) is a 128-bit value written as 32 hex digits in five groups, like 3f2b0c4e-8a1d-4f6b-9c2e-7d5a1b3c9e0f. GUID and UUID are two names for the same thing — GUID is the Microsoft term, UUID the standards term (RFC 4122).
What does version 4 mean?
UUID version 4 is the random variant: 122 of the 128 bits come straight from a random source, and the remaining 6 encode the version and variant. It's the version you want for IDs in databases, APIs, and distributed systems where no coordination is possible.
Are these GUIDs really unique?
Practically, yes. With 122 random bits there are about 5.3 undecillion possible values, so the chance of two independently generated v4 UUIDs colliding is negligible — you'd need to generate billions per second for centuries to have a meaningful probability of one duplicate.
How random are the GUIDs from this page?
They come from your browser's crypto API (crypto.randomUUID, backed by a cryptographically secure random number generator) — not from Math.random. That's the same quality of randomness your browser uses for TLS.
Can I generate GUIDs in bulk?
Yes — set how many (up to 1000), and copy them all with one click. Formatting options (uppercase, braces, no hyphens) apply to the whole batch without regenerating it.
Does anything leave my browser?
No. Generation happens entirely in your browser, so the GUIDs are never sent to a server, logged, or shared — nobody else ever sees them.
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