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UUID Generator

Generate v4 and v7 UUIDs in bulk.

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Questions
Should I use v4 or v7?
Use v7 for database primary keys. Its leading 48 bits are a millisecond timestamp, so generated values sort chronologically and insert sequentially into a B-tree index instead of scattering writes across it. Use v4 when you specifically want values that reveal nothing about when they were created.
Can two v4 UUIDs collide?
In principle yes, in practice no. A v4 UUID carries 122 random bits. You would need to generate roughly 2.7 × 10^18 of them before reaching a 50% chance of a single collision.
Are these generated securely?
Yes, using crypto.getRandomValues() in your browser. Nothing is requested from or sent to a server.