Free UUID Generator, Create Version 4 UUIDs Instantly

A UUID is a 128-bit identifier written as 36 characters - 32 hex digits split into five groups by hyphens. The point of it is coordination-free uniqueness: any machine can generate one at any time, without asking a central server, and be confident nobody else will ever produce the same value. That property is what makes UUIDs the default for distributed systems, where waiting on a database to allocate the next sequential id is either a bottleneck or impossible. Version 4 - what this tool generates - takes 122 of those bits from a random source, leaving about 5.3 undecillion possibilities. The practical meaning of that number is that you would need to generate roughly a billion UUIDs per second for 85 years before a 50% chance of a single collision. This uses the browser's crypto.randomUUID(), a cryptographically secure source, not the ordinary random function. Nothing is transmitted.

Key benefits

• Cryptographically secure randomness via crypto.randomUUID(), not a predictable pseudo-random source.
• Batch generation, so seeding test data is one operation.
• Runs in your browser - no request, no logging, no rate limit.
• Standards-compliant version 4 output that any language and database will accept.
• Instant, with no account.

How to use it, step by step

1. Choose how many you need. Generate one, or a batch when seeding test data or creating several records at once.
2. Generate. Values come from your browser's crypto.randomUUID(), the same class of randomness used for security keys.
3. Copy the result. Copy a single value or the whole batch straight into your code, migration or spreadsheet.

Common use cases

• Primary keys in a distributed system where sequential ids would need central coordination.
• Correlation ids that follow a request across multiple services in logs.
• Seeding a test database with realistic unique identifiers.
• Idempotency keys so a retried API call cannot create a duplicate record.
• Filenames for uploads, avoiding collisions without checking what already exists.

Pro tips

• Do not treat a UUID as a secret. It is unguessable in practice, but it is an identifier, not an access token.
• Store UUIDs in a native uuid column where your database has one - Postgres uses 16 bytes, while storing the text form costs 36.
• Be aware that random v4 UUIDs as a clustered primary key hurt insert performance in some databases, because each write lands at a random point in the index. UUID v7 exists to solve exactly that.
• They are case-insensitive by convention and usually written lowercase. Compare them consistently or normalise on the way in.
• To check whether an existing UUID is well-formed and which version it is, use the UUID Validator.

Common mistakes to avoid

• Using a UUID as a security token. Unpredictable is not the same as secret - anything that leaks it grants access.
• Storing them as VARCHAR(36) at scale, which more than doubles the storage and index size versus a native uuid type.
• Assuming a v4 UUID encodes a timestamp or ordering. It carries no information at all - it is pure randomness.
• Generating them with Math.random() in your own code, which is not cryptographically secure and can produce collisions.
• Exposing UUID primary keys in URLs and assuming that makes records private. It obscures them; it does not protect them.

Frequently asked questions

How do I generate a UUID?

Click generate above. Values are produced by your browser's crypto.randomUUID() and can be copied straight out - nothing is sent to a server.

Is this UUID generator free?

Yes. No account, no limit on how many you generate and no server involved.

What UUID version does this generate?

Version 4, the random-based variant, which is the standard choice for general-purpose identifiers and the one most libraries default to.

Could two UUIDs ever collide?

In theory yes, in practice no. Version 4 has 122 random bits, about 5.3 undecillion values. You would need roughly a billion per second for 85 years to reach a 50% chance of one collision - which is why they are trusted without central coordination.

Can I generate multiple UUIDs at once?

Yes. Choose a count and generate them as a batch, which is the usual need when seeding test data or creating several records.

Are these UUIDs cryptographically secure?

The randomness is - crypto.randomUUID() uses the same secure source as cryptographic key generation. But a UUID is still an identifier, not a secret, so do not use one as an authentication token.

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Ready to get started? Open the UUID Generator and try it now - completely free.