What is the difference between UUID v4 and UUID v7?

UUID v4 is entirely random (122 bits of entropy), whereas UUID v7 (RFC 9562) embeds a 48-bit millisecond timestamp in the leading bytes followed by 74 bits of randomness. UUID v7 is naturally sortable by time and significantly improves database index performance.

Can I generate thousands of UUIDs safely here?

Yes, all UUID generation runs locally on your browser via crypto.getRandomValues(). It is extremely fast and entirely private.

Dev Tools · Identifiers

UUID / GUID Generator

Generate RFC-compliant UUID v4 (random), UUID v7 (time-sorted), and decode existing UUIDs. 100% in-browser.

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Bulk Generator Count: 5

Quantity 5

Why UUID v7 is Better for Databases

Traditional UUID v4 is completely random, causing index fragmentation and heavy random I/O writes in relational database B-Trees (PostgreSQL, MySQL, SQLite).

UUID v7 (RFC 9562) fixes this by placing a 48-bit millisecond Unix timestamp at the front of the identifier. This makes records naturally sequential in time while preserving collision resistance with 74 bits of entropy.

What is the structure of a UUID v7?

UUID v7 consists of 32 hexadecimal characters divided into 5 groups (8-4-4-4-12). The first 12 hex characters represent the Unix millisecond timestamp, followed by version 7 and random bits.

Can I decode the creation date from a UUID v7?

Yes! Switch to the Inspect / Decode tab above and paste any UUID v7 to extract the exact date, time, and millisecond when it was generated.