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UUID Generator
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Generate random UUIDs (v4) online
This UUID generator creates version 4 UUIDs - also called GUIDs in the Microsoft world - using the browser's cryptographically secure random number generator (crypto.randomUUID / crypto.getRandomValues). Generate a single ID or up to a thousand at once, in lowercase, uppercase, or without hyphens for systems that store them compactly.
What is a UUID v4?
A UUID (Universally Unique Identifier) is a 128-bit value written as 36 characters:xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx. Version 4 UUIDs are generated from random data - 122 random bits after the fixed version and variant bits. The chance of two v4 UUIDs colliding is so astronomically small (you'd need to generate billions per second for decades to reach a 50% chance) that they are safely treated as unique without any central coordination.
Where UUIDs are used
- Database primary keys - IDs that can be created on any client or shard without conflicts.
- Distributed systems - correlation IDs, request tracing, message deduplication.
- File and resource names - collision-free names for uploads and temp files.
- API keys and references - opaque, unguessable public identifiers (though for secrets, use longer random tokens).
UUID v4 vs v1 vs v7
v1 embeds a timestamp and MAC address (a privacy leak); v4 is pure randomness; the newer v7 combines a timestamp prefix with randomness so IDs sort by creation time - great for database index locality. For general use, v4 remains the safe default and is what this tool generates. Need other random values? Try the hash generator.