UUID Generator

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit identifier standardised by RFC 4122 that is practically guaranteed to be unique without any central coordination. It is represented as 32 hexadecimal digits grouped into five blocks separated by hyphens, for example 550e8400-e29b-41d4-a716-446655440000. Because 128 bits offer about 3.4 × 10^38 possible values, the chance that two independently generated UUIDs collide is astronomically small — you would need to generate billions of UUIDs per second for millions of years to see a single duplicate.

UUIDs are the backbone of distributed systems, databases and APIs everywhere. They let independent machines create identifiers without phoning home to a central authority, which makes them ideal for offline-first apps, multi-region databases, message queues and any scenario where a globally unique key is needed without the latency of a coordination round-trip.

UUID versions explained

RFC 4122 defines several UUID versions, each generated from a different source of uniqueness. The most widely used today is version 4, which this tool generates:

• Version 1 (time-based). Built from the current timestamp and the machine's MAC address. Sequential but leaks the host's network identity.
• Version 3 (name + MD5). Deterministic: the same namespace and name always produce the same UUID using MD5 hashing.
• Version 4 (random). 122 of the 128 bits are filled with cryptographically secure random data. This is what most developers mean by "a UUID".
• Version 5 (name + SHA-1). Like version 3 but uses SHA-1 instead of MD5; preferred over v3 when security matters.
• Version 7 (time-ordered, 2022). Combines a millisecond timestamp with random bits so UUIDs stay sortable by creation time — useful for database indexes.

This generator produces version 4 UUIDs because they are the safest default: they require no network access, reveal no host information, and are random enough to be used as primary keys, request IDs and session tokens out of the box.

When to use a UUID generator

UUIDs show up in an enormous range of practical situations. The most common ones include:

• Database primary keys. Use UUIDs instead of auto-increment integers so that rows created on different shards never collide.
• API request IDs. Attach a UUID to each request so clients and servers can trace a transaction across logs and services.
• Session and token generation. Issue random UUIDs as session IDs, password-reset tokens and one-time links.
• File and asset naming. Give uploaded files a UUID-based name to avoid collisions and path guessing.
• Distributed messaging. Tag events in a queue or event bus with a UUID so consumers can deduplicate reliably.
• Testing fixtures. Quickly produce identifiers when seeding a test database or mocking API responses.

Anywhere you need a globally unique label without a central authority, a UUID is the standard answer.

UUID vs GUID

UUID and GUID are two names for the same concept. GUID (Globally Unique Identifier) is Microsoft's term, popularised by the Windows COM ecosystem and the .NET framework, while UUID (Universally Unique Identifier) is the name used by the IETF in RFC 4122. The binary layout is identical: 128 bits with the same version and variant fields. A GUID generated on Windows and a UUID generated on Linux can be compared directly and will follow the same string format of 32 hex digits separated by hyphens.

The only practical differences are cosmetic. Microsoft tooling sometimes wraps a GUID in curly braces (e.g. {550e8400-e29b-41d4-a716-446655440000}) and may use uppercase letters, while the RFC and most Unix tooling prefer lowercase without braces. If you need to match a Microsoft format, switch this generator to uppercase and wrap the output in braces yourself — the underlying bytes are identical.

How to generate a UUID

Generating a UUID with this tool takes only a second and happens entirely inside your browser. No upload, no sign-up, and no installation are required. Follow these three steps:

1. Choose how many and which case. Pick a count from 1 to 10 and select lowercase or uppercase output.
2. Generate. Click "Generate" to produce fresh UUIDs. Each click creates brand-new random values.
3. Copy. Click "Copy" to copy the UUIDs to your clipboard, or "Clear" to wipe the output and start again.

Because every UUID is generated locally with JavaScript on your own device, using the browser's cryptographic random source, your identifiers never leave your browser. This makes the tool completely private and safe to use for session tokens, request IDs and other sensitive values.