A 128-bit universally unique identifier. Format: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.

v4 (random) is recommended. v1 includes timestamp and MAC address which may be a privacy concern.

Practically impossible. You'd need 1 billion/second for 86 years for 50% collision chance.

When should I use UUID v4 vs UUID v7?

Use UUID v4 for general-purpose unique IDs where order does not matter. Use UUID v7 (time-based) for database primary keys, as its timestamp prefix enables chronological sorting and better index performance.

Can I use UUIDs as database primary keys?

Yes, but random UUIDs (v4) cause index fragmentation in B-tree databases. Use UUID v7 (time-ordered) or ULID for better insert performance. Alternatively, use sequential integer IDs with UUIDs as public-facing identifiers.

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What is UUID?

UUID (Universally Unique Identifier) is a 128-bit identifier that is unique across all devices and time. It's commonly used for database primary keys, session IDs, and distributed systems.

Format: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx (Version 4 - Random)

UUID Versions

Version 1: Based on timestamp and MAC address

Version 4: Randomly generated (most common)

Version 5: Based on namespace and name using SHA-1

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What is UUID?

UUID Versions

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