Rechnerpilot tool

UUID Generator

Generate UUID v4 locally with correct version and variant bits.

Developer Tools

With hyphensUppercase

Explanation

How UUID Generator works

The UUID generator creates Universally Unique Identifiers directly in the browser. UUID v4 is based on 122 bits of cryptographic randomness and is the most widely used UUID type for applications without a time reference.

The standard format uses hyphens: 8-4-4-4-12 hexadecimal characters (e.g. 550e8400-e29b-41d4-a716-446655440000). Bits 48-51 encode the version (4), bits 64-65 the variant (10). You can also generate compact UUIDs without hyphens or in uppercase.

Generation uses the browser's Web Crypto API (crypto.randomUUID or crypto.getRandomValues) for cryptographically secure random values.

Common mistakes

Using a UUID as a security feature: UUIDs are unique, but not secret. They are not suitable as access tokens or password substitutes.
Treating uniqueness as guaranteed: UUIDs are unique with astronomically high probability, but offer no mathematical guarantee. Absolute uniqueness requires central registration.
Using UUID v4 for sortable records: UUID v4 has no temporal order. For sortable IDs, UUID v7 (RFC 9562) or ULID are better suited.
Using UUIDs as a database index without considering performance: Random UUIDs can cause fragmentation in B-tree indexes. UUID v7 or sequential IDs perform better as primary keys.

Limits of this tool

UUID v4 only — no support for v1 (time-based), v5 (name-based) or v7 (time-ordered).
Generated locally, no central registration or duplicate check.
Not suitable as a security token — use dedicated crypto tokens for that.
No validation of entered UUIDs — generation only.

Sources

RFC 9562: Universally Unique IDentifiers (UUIDs). IETF, 2024. Defines UUID v7 and updates UUID v4.
RFC 4122: A Universally Unique IDentifier (UUID) URN Namespace. IETF, 2005. Original definition of UUID v4.
Web Crypto API: crypto.randomUUID() — W3C/MDN. Native browser API for UUID v4 generation.

Practice

Practical examples

A single UUID v4

Generate a single UUID in the standard format with hyphens.

IDs for test data

Generate several UUIDs without hyphens for compact test data.

Uppercase UUIDs

Use uppercase when a target system expects this format.

FAQ

Frequently asked questions

Which UUID version is generated?

The generator creates UUID v4 (RFC 4122/RFC 9562), which is based on cryptographic random values and suitable for IDs in tests and applications.

Are the UUIDs stored?

No. The UUIDs are generated locally in the browser and not sent to a server. After closing the page they cannot be recovered.

Can I copy UUIDs without hyphens?

Yes. Disable the 'With hyphens' option and the UUIDs are output as compact 32-character strings.

How likely is a UUID collision?

UUID v4 has 122 random bits and thus a very large space. With a correct random source, collisions are practically very unlikely, but neither mathematically ruled out nor centrally checked.

Can I use a UUID as a security feature?

No. Although UUID v4 is based on randomness, they are not intended as security tokens. They are publicly visible and not secret. For security purposes, use dedicated token generators with sufficient entropy.

What is the difference between UUID v4 and UUID v7?

UUID v4 (RFC 4122) uses random values only. UUID v7 (RFC 9562) combines a timestamp with randomness and is sortable — better for database primary keys. This generator creates UUID v4.

Are UUIDs globally unique?

UUIDs are unique with extremely high probability, but not guaranteed. There is no central registry. Uniqueness is based on the enormous size of the random space (2¹²² possibilities).

Which systems accept UUIDs?

UUIDs are universally usable: databases (PostgreSQL UUID type, MySQL), APIs, distributed systems, message queues, microservices, configuration files and anywhere unique identifiers are needed.

Why does the generator use crypto.randomUUID?

crypto.randomUUID() is the native browser API for UUID v4 generation and uses the operating system's cryptographic random generator. As a fallback, crypto.getRandomValues() with manual UUID formatting is used.

Can I use the generated UUIDs in production systems?

They conform to the UUID v4 layout per RFC 9562. Whether they fit in the target system depends on its format, uniqueness and security requirements.

Tips

Good to know

UUID v4 uses 122 random bits; there is no collision guarantee.
The format is standardised: 8-4-4-4-12 characters with hyphens.
Generation uses crypto.randomUUID or crypto.getRandomValues.

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