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UUID Generator

Generate random version 4 UUIDs — the 128-bit identifiers used for database keys and unique IDs — in bulk, from the browser's cryptographically secure randomness. Up to 500 at once.

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Quick Answer

Generate version 4 (random) UUIDs — 128-bit identifiers like the ones used for database primary keys — one per line, up to 500 at a time. Each is built from the browser's cryptographically secure random generator, with 122 random bits and 6 fixed bits marking it as version 4. The odds of two ever colliding are astronomically small. It runs entirely in your browser, so the IDs never leave your device.

What the UUID Generator Does

Choose how many you need and the tool prints that many random UUIDs, each in the standard 8-4-4-4-12 hexadecimal layout with the version digit fixed at 4. They are ready to paste into code, a database seed, a config file or a test fixture.

Every UUID is independent and random — there is no counter, timestamp or machine address in a version 4 UUID, so they reveal nothing about when or where they were made. That is the trade-off versus the newer time-ordered versions: maximum unpredictability, no built-in ordering.

How It Works

The tool calls the browser's built-in crypto.randomUUID where available, and otherwise fills the pattern from crypto.getRandomValues — both draw from the same cryptographically secure random source, not the ordinary Math.random. It then fixes the six bits that mark the identifier as version 4, variant 1.

A version 4 UUID has 122 random bits. That is the source of its uniqueness: with so many possibilities, you could generate a billion a second for decades and still not expect a single collision, which is why UUIDs can be created independently on many machines without coordination.

Generation algorithm

  1. Take the count. Read how many UUIDs you asked for, capped at 500.
  2. Draw secure random bits. Use the browser's cryptographic random generator (crypto.randomUUID or getRandomValues), not Math.random.
  3. Set the version and variant. Fix the six bits that mark the value as version 4, variant 1, leaving 122 bits random.
  4. Format and list. Write each as the 8-4-4-4-12 hex string, one per line.

Anatomy of a version 4 UUID

xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx 4 = version (always 4) y = variant (8, 9, a or b) x = random hex digit 122 random bits in total

Only the version and variant positions are fixed; everything else is cryptographically random.

Privacy

The UUIDs are generated in your browser from its own secure random source; nothing is requested from or sent to a server, so the values are yours alone.

A version 4 UUID contains no personal data, timestamp or device identifier — it is pure randomness — so it does not leak when or where it was created, unlike the time-based UUID versions.

Technical Details

Version4 (random)
Format8-4-4-4-12 hex, 36 characters
Random bits122 of 128
Randomnessbrowser crypto (not Math.random)
Batch size1 to 500
Caselowercase hex
Where it runsIn your browser — nothing uploaded

Standards & references

  • UUID version 4 (RFC 9562) — the current UUID standard, which superseded RFC 4122 in 2024; version 4 is the fully random variant, 128 bits with 122 of them random.
  • Cryptographic randomness — the IDs come from the browser's secure random generator (the Web Crypto source), not Math.random, so they are unpredictable as well as unique.
  • Collision odds — with 122 random bits a clash is about one in 2 to the power 122; you would need to generate billions per second for decades to expect even one.

Accuracy & Limitations

These are version 4 (random) UUIDs. They are unpredictable and great as opaque keys, but they carry no time ordering, so rows keyed by them are not sortable by creation time. If you need ordering, a time-based version (such as version 7) is a better fit.

Uniqueness is overwhelmingly likely, not mathematically guaranteed. The collision odds are about one in 2 to the power 122 — negligible — but if your system cannot tolerate even a theoretical clash, add a database unique constraint as a backstop.

Randomness quality depends on the browser's crypto generator, which is designed to be cryptographically secure. The fallback path used in older browsers draws from the same secure source, so the IDs are not the weak, predictable kind that Math.random would produce.

The values are lowercase. UUIDs are case-insensitive by the standard, but some systems compare them as plain strings; pick one case convention and stick to it to avoid mismatches.

There is a 500-per-batch cap. For a larger set, run it again — each batch is fully independent, so combining batches does not raise the collision risk in any meaningful way.

Real-World Use Cases

Database keys

Generate primary keys that can be created without a central counter.

Test data

Seed fixtures and mock records with realistic unique IDs.

Correlation IDs

Tag requests or log entries so they can be traced across services.

File and resource names

Create collision-free names for uploads or temporary objects.

When to use it — and when not to

Good for

  • Random, unguessable unique identifiers
  • Keys created independently on many machines
  • Test and seed data
  • Correlation or request IDs

Not the best choice for

  • IDs that need to sort by creation time
  • Short, human-friendly codes
  • Cryptographic secrets or tokens by themselves
  • Guaranteed-unique without a database constraint

Need time-ordered IDs for database locality? A version 7 UUID embeds a timestamp. Want a short shareable code? A nanoid or a custom short-ID scheme is more compact. Need a secret token? Use a dedicated token generator.

Frequently Asked Questions

What is a version 4 UUID?
A 128-bit identifier that is almost entirely random — 122 random bits, with 6 bits fixed to mark it as version 4. It is the most common UUID type, used wherever you need a unique ID with no central coordination.
Are these UUIDs really unique?
Effectively yes. With 122 random bits the chance of two matching is about one in 2 to the power 122. You would need to generate a billion per second for decades to expect a single collision, so for real systems they are treated as unique.
Is the randomness secure?
Yes. The tool uses the browser's cryptographic random generator (the same source as crypto.randomUUID), not Math.random, so the IDs are unpredictable as well as unique.
Why does every UUID have a 4 in it?
The 4 marks the version. In the third group, the first digit is always 4 for a version 4 UUID, and the fourth group starts with 8, 9, a or b for the variant. Those are the only fixed positions.
Can I sort records by their UUID?
Not by time. Version 4 UUIDs are random, so they have no creation order. If you need time-sortable IDs, use a version 7 UUID, which puts a timestamp at the front.
How many can I generate at once?
Up to 500 per batch. For more, run it again — the batches are independent, so combining them does not increase the collision risk.
Are UUIDs case-sensitive?
The standard says no — they are case-insensitive — but some systems compare them as plain strings. These come out lowercase; keep one convention to avoid mismatches.
Can I use a UUID as a password or token?
Not on its own. A version 4 UUID is random, but it is meant as an identifier, not a secret, and it is often stored or logged in plain sight. Use a dedicated token generator for secrets.
Do these UUIDs contain a timestamp or my device info?
No. Version 4 is pure randomness, so it reveals nothing about when or where it was made — unlike the older time- and address-based versions.
What standard defines them?
RFC 9562, published in 2024, which updated and replaced the long-standing RFC 4122. Version 4 itself is unchanged: 122 random bits with fixed version and variant markers.
Are the IDs sent to a server?
No. They are generated entirely in your browser, so they never leave your device.
What does the 8-4-4-4-12 mean?
It is the number of hex digits in each hyphen-separated group: eight, four, four, four, then twelve, for 32 hex digits and 36 characters in all.

References

Generates version 4 UUIDs (122 random bits) from the browser's cryptographic random source — crypto.randomUUID, not Math.random — and is explicit that they carry no timestamp or ordering and that collision odds (about one in 2 to the power 122) are negligible but not a mathematical guarantee.

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