UUID Generator (v4)
Generate cryptographically random UUID v4 identifiers in bulk, ready to copy.
A UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 4122. Version 4 uses random numbers, giving 122 bits of entropy—enough that collisions are practically impossible.
This generator uses the browser's crypto.getRandomValues, a CSPRNG seeded by the operating system, so the output is suitable for security-sensitive identifiers such as session tokens or request IDs.
Generated with crypto.getRandomValues, the operating system's CSPRNG. The output is suitable for session tokens, request IDs, and other security-sensitive identifiers.
Common uses
- Generating a primary key for a database row before the record is created, avoiding a round-trip to the server.
- Creating unique filenames, trace IDs, or idempotency keys for distributed systems.
Frequently asked questions
- Are UUID v4 truly unique?
- For practical purposes yes. With 122 random bits, you would need to generate about 2.7 quintillion UUIDs to have a 50% chance of one collision.
- What is the difference between v1, v4 and v7?
- v1 uses MAC address + timestamp; v4 is purely random; v7 is time-ordered and sortable, which is better for database indexes. v4 remains the most common general-purpose choice.
- Should I use Math.random() for UUIDs?
- No. Math.random is not cryptographically secure and its state can be predicted. This tool only uses crypto.getRandomValues.
- Can I get v7 instead?
- v7 is time-ordered and sortable. This tool generates v4, which is the most widely compatible general-purpose version.
- Why not use auto-increment IDs?
- Auto-increment IDs reveal record counts and are guessable. UUID v4 is random, unguessable, and can be generated anywhere without coordination.