Online UUID Generator

By Daniel DeGroff

Online UUID Generator

UUID generator

UUID (Universally Unique Identifier) is a 128-bit identifier that is used to uniquely identify information in computer systems. Version 4 UUIDs, also known as random UUIDs, are generated using random or pseudo-random numbers. Use this tool to generate random version 4 UUIDs online.


Use cases for generating UUIDs

Here are some common use cases for generating a version 4 UUID:

UUID Frequently Asked Questions

What is a UUID?

A UUID (Universally Unique Identifier) is a string of characters that is used to uniquely identify an object. You may also see the term GUID (Globally Unique Identifier) which is also commonly used. Both UUIDs and GUIDs are generated according to a standard, using a combination of random numbers, timestamps and algorithms, all of which makes it extremely unlikely that two values will be equal. It is based on the RFC 4122 standard.

What version UUID generator is this tool?

This UUID generator generates a version 4 universally unique identifier. A version 4 UUID is made up of 32 hexadecimal characters (128 bits), divided into five groups separated by hyphens in this format: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. You may also see this written as 8-4-4-4-12.

Why generate UUID version 4?

The main advantage of version 4 UUIDs is that they are generated using random numbers, which makes it extremely unlikely that two UUIDs will be the same.

How unlikely? To be specific, a UUID is 16 bytes or 128 bits. Out of these 128 bits, 4 are used to indicate the version, and another 2 indicate the variant. This leaves us with 122 bits, and as a result we have 2^122 possible combinations, or 5.3 undecillion, or 5.31x10^36 (or a 5 with 36 zeros behind it). That is a lot. When we begin talking about numbers in this range - the probability that a duplicate value will be generated is essentially zero.

This makes UUIDs perfect for use as a unique object identifier in software programs, database records, and other situations where a unique identifier is needed.

One way to think about a version 4 UUID collision is like this:

Only after generating 1 billion UUIDs every second for the next 100 years, the probability of creating just one duplicate would be about 50%. Or, to put it another way, the probability of one duplicate would be about 50% if every person on earth owned 600 million UUIDs.

How does FusionAuth use UUIDs?

In FusionAuth, UUIDs are used to identify users, applications, and other objects such as roles and groups. For example, when a new user or role is created, a UUID is generated and assigned to that user or role. This UUID can then be used to uniquely identify the user within the system, grant them appropriate resources, and it is used as a primary key in the database to store and retrieve user information. For almost every resource, FusionAuth can either generate a UUID on creation or use one supplied to the API, allowing for easier migrations of existing users, roles and other entities.