A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify objects in software. Version 4 UUIDs are randomly generated, making collisions virtually impossible. They are commonly used as database primary keys, session tokens, and API keys.
Frequently asked questions
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify objects in software systems. Version 4 UUIDs are randomly generated, making collisions virtually impossible.
What is the difference between UUID formats?
Standard format includes hyphens (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx). No-hyphens removes them for compact storage. UPPERCASE converts all letters. Braces wrap the UUID in curly braces, common in Microsoft systems.
Are generated UUIDs truly unique?
v4 UUIDs have 122 bits of randomness. The probability of generating two identical UUIDs is approximately 1 in 5.3 × 10³⁶ — effectively zero for any practical application.
What are UUIDs used for?
UUIDs are commonly used as database primary keys, session tokens, file identifiers, API keys and anywhere a globally unique identifier is needed without a central authority.