Question 1

What is a UUID and why should I use one?

Accepted Answer

A UUID (Universally Unique Identifier) is a 128-bit value designed to uniquely identify information in distributed systems without central coordination. UUIDs are practically unique, with extremely low probability of duplication, making them perfect for database keys, distributed systems, transaction IDs, and any situation requiring unique identifiers without a central authority.

Question 2

What's the difference between UUID versions?

Accepted Answer

UUID v1 uses timestamp and MAC address, making it traceable and chronologically sortable. UUID v4 uses random numbers, offering the best security and privacy. UUID v5 creates deterministic IDs by hashing a namespace and name, useful when you need consistent IDs for the same input. For most applications, UUID v4 is recommended as it provides the best balance of uniqueness and security.

Question 3

How unique are UUIDs? Can there be collisions?

Accepted Answer

UUIDs have 2^128 (approximately 3.4 × 10^38) possible values. The probability of generating a duplicate UUID v4 is incredibly small. To put it in perspective, you would need to generate about 2.71 quintillion UUIDs to have a 50% chance of finding a single duplicate. This makes UUIDs practically unique for virtually all applications.

Question 4

Can I use UUIDs as database keys?

Accepted Answer

Yes, UUIDs are excellent for database primary keys, especially in distributed systems or applications that need to generate IDs without consulting a central database first. While UUIDs take more storage space than sequential integers, they offer advantages like being globally unique without coordination, secure (v4), and allowing client-side ID generation before database insertion.

Version	Generation Method	Best Used For
Version 1	Based on timestamp and MAC address	When you need chronological ordering or want to trace origin
Version 4	Generated using random or pseudo-random numbers	Most common usage, perfect for general-purpose identification needs
Version 5	Generated by hashing a namespace identifier and name	When you need deterministic UUIDs derived from existing identifiers

Random UUID Generator

Understanding UUID Versions

UUID Format Structure

Common Uses for UUIDs