UUID Generator
Generate cryptographically-random UUIDs in bulk. v4 (random), v1 (time+MAC), v7 (timestamp+random). Click any UUID to copy.
Text & dev tools
v4 — fully random, 122 bits of entropy. Standard choice for almost everything.
Bulk mode is useful for seeding test databases or generating IDs for fixtures.
Affects the "Copy all" and "Download" output only. On-screen list is always one per line.
v4 for almost everything — databases, API keys, session IDs.
v1 when you need sortability by creation time (but it leaks your MAC address — don't use on public-facing systems).
v7 for new systems needing time-sortable IDs (2024 standard) — sortable by creation time without leaking MAC.
Click "Generate" to produce UUIDs. Click any UUID to copy it.
What is a UUID?
A UUID (Universally Unique Identifier) — also called GUID in Microsoft-land — is a 128-bit identifier that's effectively guaranteed to be unique without any central coordination. The standard format is 32 hex digits laid out in five groups separated by hyphens:
xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx
The M nibble encodes the version (1, 4, 7, etc.) and the N nibble encodes the variant (almost always 8–b for RFC 4122). At 122 bits of entropy for v4, the chance of collision is so astronomically low that generating duplicates by accident is the least of your worries.
- v4 (random) — 122 random bits. Use this by default. Cryptographically random via
window.crypto.getRandomValues. - v1 (time + MAC) — Encodes a 60-bit timestamp (100-nanosecond intervals since 1582-10-15) plus your network card's MAC. Sortable but leaks hardware identity.
- v7 (time + random) — Newer (2024 standard). 48-bit Unix-millisecond timestamp + 74 random bits. Sortable AND random — best of both worlds for new systems.
UUID Generator — FAQ
Are these UUIDs safe to use as database primary keys?
Yes — that's their most common use case. v4 in particular is ideal because it's evenly distributed across hash indexes (no hotspots), unpredictable (so URLs can't be enumerated), and collision-free for any practical dataset size. For PostgreSQL with uuid columns, paste the generated UUID directly. For MySQL with BINARY(16), strip the hyphens first.
How random is v4, really?
This generator uses crypto.getRandomValues, the same Web Crypto API that secures TLS handshakes. It pulls from the operating system's cryptographically-secure random source (e.g., /dev/urandom on Linux, BCryptGenRandom on Windows). That's the same source your browser uses to generate TLS keys — far stronger than Math.random().
What's the difference between UUID and GUID?
Nothing practical. UUID is the IETF standard (RFC 4122); GUID is Microsoft's name for the same thing. The byte layout is identical. The only minor difference: Microsoft tooling sometimes wraps them in curly braces {...} — that's what the "Braces" format option is for.
Why would I want v7 instead of v4?
If you store IDs in a B-tree index (the default for most databases), v4's pure randomness causes page splits and fragmentation. v7 IDs are time-ordered, so new rows append to the end of the index — better cache locality, smaller index size, faster inserts at scale. Use v7 for any new system that needs sortable IDs.
Can I generate the same UUID twice?
Theoretically yes, practically no. The probability of a single v4 collision among 103 trillion generated IDs is about 1 in a billion. To put that in perspective: if you generated 1 billion UUIDs per second for 85 years, you'd still have less than a 50% chance of a single duplicate. Use them without worrying.