Free Online UUID Generator (v1, v3, v4, v5, v6, v7 and more)

What Is a UUID?

A UUID is a 128 bit number written as 32 hex characters in five groups, like 6ec83519-7a47-4874-a1c6-3c7a30a8e079. A machine can generate random v4 values without a central counter. With independent uniform randomness, the collision probability is small but not zero. UUIDs can identify database rows, files and sessions across systems, with uniqueness constraints where duplicates would cause a problem.

What makes a UUID different from a plain number

• 128 bits. About 340 undecillion possible values, which is 340 followed by 36 zeros.
• One fixed layout. 32 hex digits in groups of 8, 4, 4, 4 and 12, the same in every language and database. The first digit of the third group is the version.
• No central counter. Separate devices can generate random UUIDs without asking a shared service for the next number. This does not guarantee that duplicates are impossible.
• Nothing to count. A random v4 UUID does not reveal how many records exist or which one came first, unlike an auto increment id. A time ordered v7 does carry its creation time, and that is the point of it.
• Same thing as a GUID. Microsoft calls them GUIDs. The format and the values are identical.

Where you will meet them

• Database keys. As primary keys, especially when rows are created on more than one machine or before they reach the database.
• Files, sessions and devices. Naming uploads, tagging a login session, identifying a device without using its hardware address.
• APIs and events. Request ids in logs, message ids in queues, anything you need to trace across services.

UUID versions explained

The version digit is the first character of the third group in an RFC variant UUID. It describes the layout and generation method. Nil and max are special values. This generator supports v1, v3, v4, v5, v6 and v7, plus nil and max. For the other layouts, read all UUID versions explained. To compare random and timestamp based identifiers, read UUID v4 vs v7.

Which version should I use?

• You need a random identifier: v4. It needs no central counter and does not encode a timestamp or record count.
• It will be a primary key: consider v7. Timestamp grouping can improve locality compared with random v4 keys. Benchmark your workload and read our guide to UUIDs as primary keys for storage and ordering trade offs.
• The same input must always give the same id: v5, for example to turn a customer number or a URL into a UUID on any machine without a lookup.
• An existing system requires it: v1 or v3, matching what is already there.

Why there is no v2 or v8 generator

Two versions are missing from the dropdown on purpose, for different reasons.

• v2 uses DCE security identifiers. Its layout includes a local user or group identifier and reduces timestamp precision. Libraries such as Google's Go UUID library implement it. Our browser generator does not generate v2. Our validator recognises its version number without decoding its DCE fields.
• v8 requires an application specific layout. RFC 9562 defines UUID v8 with fixed version and variant bits, leaving 122 bits for the application. A timestamp, shard identifier or hash only has meaning when the producer and reader agree on that layout. This generator provides defined v1, v3, v4, v5, v6 and v7 formats instead.

Format options

A UUID is 128 bits. How it is written is a habit of the platform, and the checkboxes above cover the common ones.

• Standard: b076e3c8-fe3c-4475-bad6-bb9dfcc13c0c, lowercase hex with hyphens in the RFC text layout.
• Uppercase: B076E3C8-FE3C-4475-BAD6-BB9DFCC13C0C, the same UUID with uppercase hex digits. Check which text formats your receiving parser accepts.
• Braces: {b076e3c8-fe3c-4475-bad6-bb9dfcc13c0c}, the Windows registry and COM style.
• No hyphens: b076e3c8fe3c4475bad6bb9dfcc13c0c, 32 hex characters, used when a system stores the value as text but wants it compact.
• Quotes: wrap the result in double quotes for a JSON string or a string literal in your code.
• Base64: the 16 bytes encoded as 22 characters without padding, shorter than the 36 character hyphenated form. Your receiving system must support this encoding.

UUID example and anatomy

UUID text uses this 8-4-4-4-12 layout. This example is v4: the 4 that opens the third group is the version, and the a that opens the fourth group contains the RFC variant bits. Six bits are fixed by the version and variant; the other 122 bits are random. A v7 such as 01a0fa69-6c6a-776c-86f2-c9be3e2b7392 opens with its timestamp instead, which the validator decodes to 2 October 2026, the day it was generated. New to the idea? Start with what a UUID is, in plain English. To see what is inside any UUID, paste it into the validator and decoder.

Generate a UUID in your language

UUID support depends on the language, library and runtime version. Our guides show generation calls, validation and limitations for JavaScript, Python, Java, Go, C#, PHP, Ruby, Rust, PostgreSQL and MySQL.

How this generator works and what it keeps

The page uses the open source uuid package from npm, running on your browser's cryptographic random source. Random values come from crypto.getRandomValues, time based ones from your clock, name based ones from hashing in JavaScript. No request is made to our server when you click Generate, and we never see, store or log a value. You can confirm that in your browser's network tab. The 1000 per batch limit is only there to keep the page responsive. For the design decisions behind each option, read Inside our UUID generator.

Frequently asked questions

Is a UUID really unique?

For random v4 there are 2 to the power 122 possible values. Assuming independent uniform random choices, generating about 103 trillion gives roughly a one in a billion chance of a duplicate. The chance is small, but it is not zero. Keep a uniqueness constraint where duplicate identifiers would cause a problem. The maths is in our post on UUID collision probability.

What is the difference between UUID and GUID?

None in the value. GUID is Microsoft's name for the same 128 bit identifier, and Guid.NewGuid() in .NET makes a standard v4 UUID. GUIDs are often shown uppercase or in braces, which are just formats. More in UUID vs GUID.

Which version is best for a database primary key?

v7 groups keys by their encoded timestamp, which can improve index locality compared with random v4 keys. It does not guarantee append order across clock changes or concurrent writers. Check your generator and benchmark your database workload before choosing a key type.

Can I generate UUIDs in bulk?

Yes, up to 1000 per click here, and you can download the batch as a text file, a JSON array or a CSV. Run it again for more. For millions, generate them in your own code, our language pages show how.

Are the UUIDs made here safe to use in production?

Yes. They come from the browser's cryptographic random source through a standard library, which is the same quality you get from a server side generator. They are not stored or transmitted, so nobody else has them. That said, UUIDs are identifiers, not secrets. Do not use one as a password or an API key.

Why can I not generate v2 or v8 here?

v2 needs DCE security identifier fields that this browser generator does not provide. v8 needs an application specific layout. We generate v1, v3, v4, v5, v6 and v7, plus nil and max. The section above links to the format definitions and a library that supports v2.

Is this generator free?

Yes, with no account and no limits beyond the 1000 per batch. The site is supported by a small number of ads.