UUID Generator

UUIDs (Universally Unique Identifiers) are 128-bit labels designed to be globally unique without a central authority. They're the default choice for distributed system primary keys, session IDs, and correlation IDs.

UUID versions

- **v1**: Timestamp + MAC address. Sortable and traceable, but leaks the generating machine's MAC address. Largely replaced by v7. - **v4**: 122 bits of random data from a cryptographically secure random number generator. The most commonly used variant. Not sortable. - **v7**: Timestamp (millisecond precision) in the high bits, random in the low bits. Sortable by creation time, making them ideal for database primary keys that need efficient B-tree indexes.

Why UUID v7 for database primary keys?

Random UUIDs (v4) cause index fragmentation in relational databases. Each insert goes to a random position in the B-tree index, causing frequent page splits and poor cache locality. UUID v7's time-sorted prefix means new rows append near the end of the index, just like auto-increment integers — with all the distributed-uniqueness benefits of UUIDs.

Bulk generation

This tool lets you generate up to 10,000 UUIDs at once. Use the copy-all or download-as-text buttons to export them for seeding test databases, generating batch job IDs, or producing test fixtures.