Cryptographic randomness
Every UUID draws from crypto.getRandomValues / crypto.randomUUID — the browser's CSPRNG — so identifiers are unpredictable and collision-resistant by design.
Developer Tools
UUID Generator (v4 & v7)
Random v4 or sortable, time-ordered v7 — generated in bulk with your browser's secure random source, formatted exactly how your codebase wants them.
In short
Generate cryptographically secure UUIDs online: random v4 or time-ordered v7, up to 1000 at once, with uppercase, braces and no-hyphen formats. Free, private.
By NaveenKumar T · Updated
Learn: UUID v4 vs UUID v7: Which Should You Use for Database Keys?
- v4 (random) & v7 (time-ordered)
- Bulk generate up to 1000
- UPPERCASE, braces, no-hyphens
Runs entirely in your browser — nothing you paste or open here is uploaded, logged, or stored.How we handle data →
Why this tool
The right UUID version, properly random
Not all UUIDs are equal: v4 maximizes entropy, v7 adds database-friendly time ordering. Both come from your browser's CSPRNG — not Math.random().
v7 for databases
UUIDv7 (RFC 9562) leads with a 48-bit Unix timestamp, so values sort by creation time — B-tree indexes stay compact where random v4 keys fragment them.
Your codebase's format
Uppercase for .NET, braces for COM/registry style, hyphen-less for compact storage — formatting toggles apply instantly to the whole batch.
Inspector included
Paste any UUID to read its version and variant bits — and for v1/v7, the embedded creation timestamp, decoded to your local time.
Learn more
UUIDs in 60 seconds
A UUID is a 128-bit identifier written as 32 hex digits in a 8-4-4-4-12 pattern. Its promise is uniqueness without coordination: any machine can mint one with effectively zero collision risk, which is why UUIDs anchor distributed systems, event streams, and offline-first apps where a central ID sequence is impossible.
Version 4 fills 122 bits with randomness. Version 7 — standardized in RFC 9562 (2024) — spends the first 48 bits on a millisecond Unix timestamp and the rest on randomness, making values time-sortable. If you've ever watched a Postgres index bloat under random v4 primary keys, v7 is the fix that keeps UUID ergonomics.
Worked example
Two identifiers produced by this generator — one v4, one v7 — split group by group so the version and variant bits stop being folklore. Both are 32 hex digits in the same 8-4-4-4-12 layout; what differs is how much of that space is random and how much is structure.
Read the v7 value's first two groups as one 48-bit big-endian integer: 0x01a08b506495 is 1,789,043,696,789 milliseconds since the Unix epoch, which is 2026-09-10T12:34:56.789Z. That prefix is why a column of v7 keys sorts chronologically as plain text, while v4 keys land in random index pages.
| Segment | v4 example | v7 example |
|---|---|---|
| Group 1 — 32 bits: pure randomness in v4; the high 32 bits of the 48-bit millisecond timestamp in v7 | 68986dd7 | 01a08b50 |
| Group 2 — 16 bits: pure randomness in v4; the low 16 bits of that same timestamp in v7 | cad4 | 6495 |
| Group 3 — 16 bits: the first hex digit is the version (4 or 7); the remaining 12 bits are random in v4 and a per-millisecond monotonic counter in v7 (here 0x0d8) | 4b4a | 70d8 |
| Group 4 — 16 bits: the top two bits are the variant — hex a is 1010 and hex b is 1011, both starting 10, the RFC 4122/9562 family — and the remaining 14 bits are random | a1fd | bbba |
| Group 5 — 48 bits: random in both versions | 3b10b06805e5 | f55254a0e387 |
Help
Frequently asked questions
Everything you need to know about the UUID Generator.
01Should I use UUID v4 or v7?
v4 when identifiers must be unguessable and unordered (tokens, public IDs). v7 when they're database primary keys: the leading timestamp keeps inserts roughly sequential, which dramatically reduces index fragmentation versus v4. v7 does reveal creation time — don't use it where that's sensitive.
02How likely is a collision?
v4 carries 122 random bits. You'd need to generate about 2.7×10¹⁸ UUIDs for a 50% chance of one collision — billions per second for a century. For practical purposes, treat them as unique without checking.
03What do the inspector's 'version' and 'variant' mean?
Four bits in the third group encode the version (the generation algorithm: 4 = random, 7 = Unix-time-ordered, 1 = legacy MAC+time), and two-three bits in the fourth group encode the variant (the layout family — modern UUIDs are all RFC 4122/9562). The inspector also decodes the embedded timestamp for v1 and v7.
04Are these UUIDs safe to use in production?
These UUIDs are generated by your browser's cryptographically secure random source, the same quality your server runtime provides, and v7 follows RFC 9562 bit-for-bit. Nothing is logged or transmitted, so the values exist only on your machine.
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