UUID Generator

UUID Version

All zeros — the null UUID Timestamp + random node MD5 hash of namespace + name Cryptographically random SHA-1 hash of namespace + name

Namespace

Name

Quantity

Generated UUIDs ()

Click Generate to create UUIDs

UUID Validator Paste any UUID to check its validity and detect its version

Invalid UUID

Valid UUID

Version
Variant
Normalized

NIL UUID (all zeros)

What is UUID v4?

UUID v4 generates 122 bits of random data using a cryptographically secure random number generator. It is the most common UUID version and the best choice when you don't need deterministic IDs.

Name-Based UUIDs (v3 & v5)

v3 uses MD5 and v5 uses SHA-1 to hash a namespace UUID + a name. Given the same inputs, they always produce the same UUID — making them ideal for reproducible IDs like resource identifiers.

When to use UUIDs?

UUIDs are used as primary keys in databases, unique file names, session tokens, API resource identifiers, and distributed system IDs. Unlike auto-increment integers, UUIDs work across multiple databases without coordination.

Frequently Asked Questions

Everything you need to know about UUIDs and their versions

A UUID (Universally Unique Identifier) is a 128-bit number formatted as 32 hexadecimal characters in the pattern xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. UUIDs are used wherever you need unique IDs without a central authority — database primary keys, file names, session tokens, API resources, and distributed system IDs. The probability of generating the same UUID v4 twice is astronomically small: about 1 in 5.3 × 10^36.

UUID v1 uses the current timestamp + a random node identifier, making it partially sortable but revealing generation time. UUID v3 uses MD5 to hash a namespace + name — deterministic but MD5 is considered weak. UUID v4 is fully random and the most commonly used. UUID v5 uses SHA-1 to hash namespace + name — deterministic and stronger than v3. NIL is all zeros, used as a null/empty value.

For most applications, UUID v4 is the best choice — it is random, collision-resistant, and doesn't leak information. Use v5 when you need reproducible IDs from the same input (e.g. converting usernames to UUIDs deterministically). Use v1 only if you need time-sortable IDs and understand the timestamp information it encodes. Avoid v3 (MD5) in new systems.

UUID v4 has 122 random bits, giving 2^122 possible values (~5.3 × 10^36). At 1 billion UUIDs per second, you would need about 85 years to have a 50% probability of a single collision. For practical purposes, UUIDs are unique. UUID v3/v5 are deterministic — the same namespace+name always gives the same UUID, which is both a feature and a constraint.

Yes. This tool uses window.crypto.getRandomValues(), the same cryptographically secure random number generator used by browsers for TLS and other security functions. However, for session tokens or secrets, consider using the Token Generator tool instead — tokens are purely random, while UUIDs include version and variant bits that slightly reduce entropy.

Generate UUIDs online – v1, v3, v4 and v5

A UUID generator creates Universally Unique Identifiers: 128-bit values that are practically guaranteed to be unique without any central authority. This tool supports every common version – random v4, timestamp-based v1 and the name-based variants v3 (MD5) and v5 (SHA-1) – and produces them entirely in your browser. That makes it a fit for developers who need to label records, messages or resources without collisions.

Common use cases

Database primary keys: Assign unique IDs to table rows without depending on a server-side sequential counter.
Distributed systems: Tag messages, events or files across microservices that generate IDs independently of each other.
Name-based IDs: Use v3 or v5 to create reproducible UUIDs from a namespace and a name, ideal for deterministic keys.
Idempotent requests: Attach a UUID to API requests to reliably avoid duplicate processing on retries.

How to generate a UUID

1 Choose the UUID version you need (usually v4 for random IDs).
2 Optionally set the quantity to create several UUIDs at once.
3 For v3 or v5, also provide a namespace and a name.
4 Copy individual values or the entire list with one click.

Benefits of this UUID generator

The tool covers the full range of versions, validates existing UUIDs and handles bulk generation for test data – all without a server. For most applications v4 is the right choice because it relies on pure randomness and reveals nothing about the time or machine that created it. If you need sortable, time-based identifiers, take a look at the related ULID generator. In databases a sequential key can improve index performance depending on the engine, so weigh both options.

Free tools that pair well with this one – right in your browser, no sign-up.

Token Generator Generate secure tokens & passwords Hash Generator Calculate MD5, SHA-256 & more Bcrypt Generator Hash & verify passwords securely ULID Generator Time-sortable unique identifiers