UUID Generator

The UUID Generator creates universally unique identifiers instantly — random v4 UUIDs for general use, or time-sortable v7 UUIDs ideal for database keys. Generate one or thousands at once, copy them into your code, tests, or database, and rely on them being unique. Generated in your browser using cryptographic randomness, free, with no tracking.

What a UUID Is

A UUID (Universally Unique Identifier) is a 128-bit value built to be unique across space and time without any central coordinator. It's written as 36 characters — 32 hexadecimal digits in five hyphenated groups following an 8-4-4-4-12 pattern, like 550e8400-e29b-41d4-a716-446655440000. Standardized in RFC 9562 (which replaced RFC 4122 in 2024), it's the standard way to label a database row, file, event, session, or message when sequential integers won't do. If you've seen the term GUID, that's Microsoft's name for exactly the same thing.

How to Use It

1. Choose a version — v4 for most uses, v7 for sortable keys.
2. Generate one or many at once.
3. Copy and use in your code, database, or API.

The UUID Versions

v4 vs. v7: The Modern Choice

These two cover almost every real need. v4 is fully random — simple, supported everywhere, and revealing nothing about where it came from, which makes it the safe default for general identifiers. v7 puts a millisecond timestamp at the front followed by random bits, so its values are time-sortable. The practical rule: reach for v4 for ordinary unique IDs, and choose v7 when the UUID will be a database primary key.

How Unique Is "Unique"?

Astonishingly so. A v4 UUID has about 2^122 possible values — roughly 5.3 × 10^36. To have even a 50% chance of a single collision you'd need to generate around 2.7 quintillion of them; generating a billion every second for a century still wouldn't meaningfully risk a duplicate. For every practical purpose, you can treat UUIDs as guaranteed unique.

An Honest Note: UUIDs Aren't Security Tokens

This catches people out, so it's worth stating plainly. A UUID is an identifier, not a secret. Even random v4 UUIDs end up logged, sitting in URLs, and stored unencrypted, so they should never be your sole authentication mechanism — use signed JWTs or proper API keys for that. And avoid v1 for anything externally visible, because it can embed the generating machine's MAC address and exact creation time, leaking infrastructure details.

Why Version Matters for Databases

Here's the performance insight behind v7's popularity. Using random v4 UUIDs as primary keys means every insert lands at a random position in the database's B-tree index, causing page splits and cache misses that slow writes as your table grows. Time-ordered UUIDs (v6 and v7) insert sequentially, keeping the index compact and writes fast. If your IDs are primary keys, v7 can make a real difference at scale.

Where UUIDs Are Used

• Database primary keys — unique rows without a central sequence.
• API & resource IDs — identify objects across services.
• Distributed systems — generate IDs independently with no coordination.
• Test data & seeds — quick unique values for development.

Free, Private, and Instant

UUIDs are generated in your browser with cryptographic randomness — nothing is transmitted, stored, or tracked. Create a single UUID or generate many in bulk, then copy them straight into your work. Free, with no signup.

UUID Generator FAQs

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit value designed to be unique across space and time without any central authority. It's written as 36 characters — 32 hexadecimal digits in five hyphen-separated groups (8-4-4-4-12), like 550e8400-e29b-41d4-a716-446655440000. Because anyone can generate one independently and still avoid collisions, UUIDs are ideal for databases, APIs, and distributed systems.

Is a UUID the same as a GUID?

Yes. GUID (Globally Unique Identifier) is Microsoft's term for the same thing, used across .NET, Windows, and SQL Server. UUID is the term in the IETF standard (RFC 9562, which replaced RFC 4122 in 2024). The format and structure are identical, so the words are interchangeable.

What's the difference between UUID v4 and v7?

UUID v4 is fully random (122 random bits), simple, widely supported, and reveals nothing about its origin — the go-to choice for general-purpose IDs. UUID v7 embeds a millisecond timestamp followed by random bits, making it time-sortable. v7 is the better choice for database primary keys because its values insert in order, while random v4 values scatter across the index.

Which UUID version should I use?

For most purposes, v4 — it's random, universally supported, and safe to expose. For new database primary keys, prefer v7, which is time-ordered and far kinder to database indexes. Use v5 (or v3) when you need a deterministic ID that's always the same for a given input, and avoid v1 for anything public since it can embed your machine's MAC address.

How unique are UUIDs really? Can they collide?

For practical purposes they're unique. UUID v4 has about 2^122 possible values — roughly 5.3 × 10^36. You'd need to generate around 2.7 quintillion UUIDs to reach even a 50% chance of a single collision. Generating a billion per second for a century wouldn't meaningfully risk a duplicate, so you can safely treat them as unique.

Are UUIDs secure enough to use as passwords or tokens?

No. UUIDs are identifiers, not security tokens. Even random v4 UUIDs are routinely logged, placed in URLs, and stored unencrypted, so they shouldn't be your sole authentication mechanism. Use purpose-built tokens like signed JWTs or API keys for security. Also avoid v1 for external IDs, since it can leak the generating machine's MAC address and creation time.

Why do random UUIDs hurt database performance?

When you use random v4 UUIDs as primary keys, each insert lands at a random spot in the database's B-tree index, causing page splits and reducing cache efficiency — which slows writes at scale. Time-ordered UUIDs (v6 and especially v7) insert sequentially, keeping the index tidy and writes fast. That's the main reason v7 exists.

Is the UUID generator free and private?

Yes. UUIDs are generated in your browser using cryptographic randomness — nothing is sent to a server, stored, or tracked. Generate one or many, free and instantly, and copy them straight into your work.