**Universally Unique Identifier - a 128-bit identifier** UUID stands for "Universally Unique Identifier". The idea is that it's a [[Surrogate Keys]] that function for _any_ element of _any_ table, resource, system, or whatever. It's **universal**. It was developed my Microsoft, and is typically 128-bits. They are supported by Microsoft SQL Server, MySQL, PostgreSQL, MongoDB, and others. # Format There are 5 Versions of UUIDs. Some are random. Some are time-indexed. They generally are broken into 5 groups of **hexadecimal** characters, delimited by hyphens. Like so: `123e4567-e89b-12d3-a456-426614174000` What each of those hyphen-delimited groups _means_ depends on the version of the UUID. **** # More ## Source - [Universally unique identifier - Wikipedia](https://en.wikipedia.org/wiki/Universally_unique_identifier) ## Related - [[SysML]] - [[Primary Key]] - [[Surrogate Keys]] - [[UUIDs in the Wild]]