What is UUID?
Short answer: A UUID (Universally Unique Identifier) is a 128-bit identifier expressed as 32 hexadecimal characters in 5 groups separated by hyphens (8-4-4-4-12).
Detailed explanation
UUIDs guarantee uniqueness without central coordination: any system can generate one and the probability of collision with another UUID anywhere in the world is practically zero (1 in 5.3 × 10^36 for UUID v4). 5 versions exist: v1 based on MAC + timestamp, v3 MD5 hash of namespace+name, v4 random (most used), v5 SHA-1 hash, v7 time-orderable (new).
Example
550e8400-e29b-41d4-a716-446655440000 (UUID v4)
Common use cases
- ▸Primary keys in distributed databases
- ▸Transaction IDs in APIs
- ▸File upload IDs
- ▸Session identifiers
- ▸Tracking IDs in analytics
Frequently asked questions
What does UUID stand for?
Universally Unique Identifier: a 128-bit value written as 36 characters, designed so separate systems can generate IDs without coordinating.
Which version should I use?
Version 4, the random one, covers almost every case. Version 7 is worth knowing about because it sorts by time, which helps database indexes.
Can I use a UUID as a database primary key?
Yes, and it is common in distributed systems. The trade-off is size and index fragmentation compared with an auto-incrementing integer.
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