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UUID Generator

A UUID generator — or GUID generator, Microsoft’s name for the same thing — for cryptographically random UUIDs (version 4), one at a time or a hundred at once.

Loading UUID Generator…

Runs entirely in your browser. What you enter stays on your device — nothing is sent to a server. Verify it yourself

Can two UUIDs be the same?

In principle yes, in practice no. A version 4 UUID carries 122 random bits, so you would need to generate a billion per second for about 85 years to reach a one-in-a-billion chance of a single collision — provided the random source is genuinely random.

Cost
Free, no limits
Upload
None — runs on your device
Sign-up
Not required
Works offline
Yes, once loaded

How to generate a UUID

  1. Choose how many

    1, 5, 10, 25, 50 or 100 at a time.

  2. Set the format

    Tick Uppercase if your system wants capitals, and untick Hyphens for the 32-character form.

  3. Generate and copy

    Press Generate for a fresh set, then copy one UUID, or every one with Copy all.

Examples

  • Generate3f2504e0-4f89-41d3-9a0c-0305e82c3301

    Thirty-two hex digits in five hyphen-separated groups.

  • A batch of tenTen independent identifiers

    For seeding test data or pre-allocating IDs.

Key features of the UUID Generator

  • Version 4 (random) UUIDs
  • Generates several at once
  • One-click copy
  • Uses the browser's cryptographic random source

Supported formats

Version

  • UUID v4 (random)

At a time

  • 1
  • 5
  • 10
  • 25
  • 50
  • 100

Format

  • Lowercase or uppercase
  • With or without hyphens

When should you use this?

  • Primary keys that can be generated without asking a database.
  • Correlation IDs for tracing a request across services.
  • File names guaranteed not to collide.
  • Test fixtures needing realistic unique values.

Limitations

  • Version 4 UUIDs are random, so they do not sort meaningfully and cluster badly as database index keys. On large tables that costs real write performance, which is why UUIDv7 and similar time-ordered schemes exist.
  • A UUID is not a secret. It is unguessable in practice, but it is not authorisation, and treating it as one is a recurring source of vulnerabilities.
  • They are long. As a public URL identifier they are unwieldy compared with a short slug or a compact ID.
  • Uniqueness is probabilistic rather than guaranteed. The probability of a collision is negligible, but it is not zero.

Troubleshooting

I need a deterministic UUID from a name

That is version 5, which hashes a namespace and a name. This tool generates version 4, which is purely random and deliberately not reproducible.

My database rejects the value

Some expect the hyphens and some expect them stripped. Check the column type — a CHAR(32) will not accept a 36-character hyphenated form.

Common mistakes to avoid

  • Using a UUID in a URL as though it were an access control. Unguessable is not the same as authorised.
  • Making a v4 UUID the clustered primary key of a large, write-heavy table.

Pro tips

Tips for better results

  • Sortable IDs

    Use UUIDv7 or a ULID when order matters

    If you need identifiers that sort by creation time, look at UUIDv7 or a ULID rather than v4.

  • Storage

    Store them as UUID or binary, not as 36-character strings

    Store UUIDs as a native UUID or binary column where your database has one. Storing them as 36-character strings wastes a great deal of space on a large table.

Standards and terms behind the UUID Generator

The named things this tool works with, and the documents that define them.

UUID (RFC 9562)Specification
The IETF specification for universally unique identifiers, including the random version 4 and the time-ordered version 7. Reference: UUID (RFC 9562)
IETFWho made it
The body that publishes RFCs, including those defining WebP, FLAC, Opus, Matroska and JSON.
Positional notationHow it works
Writing a number in a base — binary, octal, decimal or hexadecimal — where each column is worth a power of that base.

Also searched as: generate a v4 uuid, random guid, bulk uuids.

What a v4 UUID is

A version 4 UUID is 122 random bits plus 6 fixed bits that identify the version and variant, formatted as 32 hexadecimal digits in five hyphen-separated groups. Those 122 bits give around 5.3 × 10³⁶ possible values.

The practical consequence is that two independent systems can generate UUIDs forever without coordinating and never collide. You would need to produce a billion UUIDs per second for about 85 years to reach a one-in-a-billion chance of a single duplicate.

Why the random source still matters

UUIDs routinely end up as session identifiers, password-reset tokens and unguessable object keys. Uniqueness alone is not enough for those jobs — they must also be unpredictable. A UUID generated from a non-cryptographic PRNG is unique and guessable, which is the worst combination. This tool uses crypto.randomUUID, falling back to crypto.getRandomValues, never Math.random.

UUIDs make poor primary keys

v4 UUIDs are random, so inserting them into a clustered index writes to random points in the B-tree rather than appending. On a large table that fragments the index and hurts insert throughput noticeably.

If you want both global uniqueness and insert locality, look at UUIDv7 or ULID — both put a timestamp in the high bits so values sort roughly by creation time while staying unique.

Privacy

The UUID Generator runs entirely in your browser. What you enter and the result it produces stay on your own device — nothing is sent anywhere, because nothing needs to be.

You can confirm this rather than take our word for it: open your browser’s developer tools, watch the Network tab, and use the tool. No request carries your input. It also keeps working with the connection off.

Details are in the privacy policy.

More generators

What next?

When you need an unguessable credential rather than an identifier.

Generate a random secret

UUID Generator — questions

Can two UUIDs be the same?

In principle yes, in practice no. With 122 random bits you would need to generate a billion per second for 85 years to reach a one-in-a-billion chance of a single collision — provided the random source is genuinely random, which is why the source matters.

What is the difference between UUID v1 and v4?

v1 derives from a timestamp and the machine's MAC address, so it is sortable but leaks where and when it was made. v4 is random, revealing nothing. v4 is the right default unless you specifically need the ordering.

Should I use a UUID as a database primary key?

It depends on scale. v4 UUIDs are random, so they fragment a clustered index and slow inserts on large tables. UUIDv7 or ULID keep global uniqueness while sorting by creation time, which avoids that problem.

Is a UUID safe to use as a secret token?

A v4 UUID from a cryptographic source has 122 bits of entropy, which is ample. A UUID from a weak random source is not — and v1 UUIDs are predictable by design. This generator uses the browser's cryptographic source.

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