UUID Standard Architecture
Universally Unique Identifier engineering. From legacy RFC 4122 to the modern RFC 9562 timestamp-ordered specifications.
UUID Version Standards5
Select the appropriate version based on your architectural requirements.
Version 7
The modern standard. Timestamp-sorted for optimal database performance (RFC 9562).
Version 4
Completely random identifiers. The most popular version for general-purpose tokens.
Version 5
Deterministic identifiers generated using SHA-1 hashing with a namespace.
Version 3
Deterministic identifiers generated using MD5 hashing with a namespace.
Version 1
Time-based identifiers that incorporate the hardware MAC address.
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The Engineering of Unique Identifiers
UUIDs are 128-bit values structured to ensure global uniqueness. The evolution of the standard from RFC 4122 to RFC 9562 has introduced optimizations for modern distributed systems and database storage engines.
Database Monotonicity
The primary advantage of Version 7 is its time-ordered prefix. In B-Tree indexes, this ensures that new rows are appended sequentially, eliminating the index fragmentation common with random Version 4 UUIDs.
Collision Probability
With $2^122$ possible random values, the chance of a UUID collision is practically zero. Even generating billions per second, it would take centuries to encounter a duplicate in a global system.
Why Standards Matter
Choosing the right UUID version is an architectural decision. While v4 is perfect for UI tokens and session IDs, v7 is the superior choice for primary keys in high-scale Postgres or MySQL instances. Deterministic versions like v3 and v5 are essential when you need to map existing strings (like URLs or account names) to a 128-bit space consistently.
Choose Your Intent
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Frequently Asked Questions
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems without significant central coordination.
Which UUID version should I use?
For most modern database applications, Version 7 is recommended due to its sortability. For simple unique tokens, Version 4 is the industry standard.
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