UUID Generator
Generate RFC 4122 compliant unique identifiers
Click "Generate UUID" to start
What is UUID?
UUID (Universally Unique Identifier) is a 128-bit identifier used to identify information in distributed systems. The standard form of UUID consists of 32 hexadecimal digits, divided into 5 groups by hyphens in the format 8-4-4-4-12, totaling 36 characters.
UUID was developed by the Open Software Foundation (OSF) and standardized as RFC 4122. The design goal of UUID is to allow all elements in a distributed system to have a unique identifier without a central coordination authority.
Usage Guide
Format Examples
- With hyphens (Standard format):
550e8400-e29b-41d4-a716-446655440000 - No hyphens (Compact format):
550e8400e29b41d4a716446655440000 - With braces (Microsoft GUID format):
{550e8400-e29b-41d4-a716-446655440000}
Keyboard Shortcuts
Ctrl + G- Generate UUIDCtrl + Shift + C- Copy All
UUID Structure
Example: 550e8400-e29b-41d4-a716-446655440000
└───┘ └─┘ └─┘ └─┘ └──────┘
Timestamp Version Variant NodeID
Format: xxxxxxxx-xxxx-Vxxx-Nxxx-xxxxxxxxxxxx
V = Version number (1, 4, 5, etc.)
N = Variant identifierFAQ
Are UUIDs really unique?
UUID v4 uses 122 random bits. While theoretically possible to have duplicates, the probability is extremely low. Generating 1 billion UUIDs, the collision probability is about 0.00000000006%. In practice, they can be considered unique.
What is the difference between UUID and GUID?
GUID is Microsoft's implementation of UUID. They are essentially the same thing. GUID typically refers to Microsoft's implementation, while UUID is the general standard. Technically, GUID is just a form of UUID.
Should I choose UUID v1 or v4?
Most scenarios recommend v4 (random) because it's simple and doesn't expose any information. v1 is timestamp-based and suitable for scenarios requiring time-based sorting, but it exposes generation time and MAC address.
Can UUID be used as a database primary key?
Yes. Advantages of UUID as primary key include global uniqueness, no need for central coordination, and can be generated client-side. Disadvantages are 36 characters take more space than auto-increment IDs, and unordered v4 may affect index performance.
Why are there letters in UUID?
UUID is a 128-bit binary number, typically represented as 32 hexadecimal digits. Hexadecimal uses 16 characters (0-9 and a-f), so UUIDs contain letters a-f.
What is Nil UUID?
Nil UUID is an all-zeros UUID: 00000000-0000-0000-0000-000000000000. It is used as a special value or placeholder to indicate "no UUID".