UUID Generator

UUID Generator: A Quick Guide

Make UUIDs of versions 4, 7, 1 and 5, one at a time or up to 1000 at once, in lowercase or uppercase, with or without hyphens and braces, and check any UUID to see its version and when it was made. Everything happens in your browser: nothing is sent anywhere or stored.

What is a UUID?

A UUID (universally unique identifier) is a 128-bit number used as an id that anyone can create without asking a central register, with no real risk that someone else ever creates the same one. It is written as 32 hexadecimal digits in five groups, 8-4-4-4-12:

f47ac10b-58cc-4372-a567-0e02b2c3d479

The first digit of the third group is the version (here 4), and the first digit of the fourth group shows the variant: 8, 9, a or b for every UUID made today. Microsoft calls the same thing a GUID (globally unique identifier), often written in capitals and in braces, such as {F47AC10B-58CC-4372-A567-0E02B2C3D479}. UUIDs are defined by RFC 9562, which replaced RFC 4122 in 2024.

How to use the UUID Generator

1. Copy the UUID that is ready when the page opens: a random version 4, the usual choice.
2. Choose a version if you need another one (see below), and set How many for a list, one UUID per line.
3. Set the format: Uppercase, Hyphens and Braces. A new UUID appears with every change, and Generate makes another.
4. Check a UUID by pasting it into the last card: it tells you whether it is valid, its version and variant, and for a time-based UUID when it was made.

Which version should I use?

• Version 4 (random): 122 random bits. The default everywhere, and the right choice when you just need an id.
• Version 7 (time-ordered): the time in milliseconds, then a 12-bit counter and 62 random bits. UUIDs made later sort later, which keeps database indexes compact and fast, so it is the best choice for primary keys. Anyone can read the creation time from it.
• Version 1 (time and node): the time in steps of 100 nanoseconds since 15 October 1582, a clock sequence and a node id. The original version, still found in older systems. The node used to be the computer's network address; this generator uses a random node instead, as RFC 9562 advises.
• Version 5 (name-based): made from a namespace and a name with SHA-1, so the same name always gives the same UUID. Use it to turn a domain, a URL or any key into a stable id, such as 2ed6657d-e927-568b-95e1-2665a8aea6a2 for www.example.com in the DNS namespace.

Two more versions exist and can be checked here: version 3, the same as 5 but with MD5, which RFC 9562 recommends against for new work, and version 6, version 1 with its time reordered so it sorts, which version 7 does better. The nil UUID is all zeros (00000000-0000-0000-0000-000000000000) and the max UUID all ones (every digit f); both mean "no UUID".

The format options

• Uppercase: F47AC10B-… instead of f47ac10b-…. Both are the same UUID; lowercase is the standard form, while Windows and .NET often show capitals.
• Hyphens: turn them off for the 32 digits alone, as some databases and file names store them.
• Braces: {…} around each UUID, the way GUIDs are written in the Windows registry and in C#.

How unique is a UUID?

A version 4 UUID has 122 random bits, so there are 2^122 of them, about 5.3 undecillion. To reach an even chance of a single repeat you would need about 2.71 quintillion of them: making a billion every second, that takes about 86 years. Even 103 trillion UUIDs carry only a one-in-a-billion chance of any repeat. Version 7 puts the time in front of its 62 random bits, so two UUIDs can only clash if they are made in the same millisecond.

That holds only if the random bits are truly random. This generator takes them from crypto.getRandomValues, the generator browsers use for encryption keys, not from the predictable Math.random. In a list of version 7 or version 1 UUIDs made in the same millisecond, the counter or the time counts on by one from UUID to UUID, so the list is unique and already in order.

Frequently asked questions

What is the difference between a UUID and a GUID?

None in practice: GUID is Microsoft's name for a UUID. A GUID made by Windows or .NET today is a version 4 UUID, often shown in uppercase and in braces, which the format options reproduce.

Can a UUID be decoded?

Only the time-based ones carry information: a version 1, 6 or 7 UUID records when it was made, which Check a UUID shows, and a version 1 UUID from an older system may hold the network address of the computer that made it. A version 4 UUID is random and a version 5 UUID is a hash, so neither tells you anything more.

How do I get UUIDs for a Minecraft Bedrock add-on?

A Bedrock pack's manifest.json needs a fresh version 4 UUID for its header and another for each module. Set How many to 2 (or one more for each extra module), copy the list and paste one UUID into each uuid field. Never reuse the UUIDs of another pack, or the game treats the two as the same.

Is the UUID valid if it uses capitals or has no hyphens?

Yes. UUIDs are compared by their digits, so F47AC10B58CC4372A5670E02B2C3D479 and f47ac10b-58cc-4372-a567-0e02b2c3d479 are the same UUID. Check a UUID accepts either, with braces or a urn:uuid: prefix too, and shows the standard form.