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
Q: Are UUIDs really unique?
A: 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.
Q: What is the difference between UUID and GUID?
A: 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.
Q: Should I choose UUID v1 or v4?
A: 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.
Q: Can UUID be used as a database primary key?
A: 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.
Q: Why are there letters in UUID?
A: 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.
Q: What is Nil UUID?
A: 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".