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UUID Generator

Generate cryptographically secure UUID v4 or timestamp-based UUID v1. Single or bulk generation up to 100. All generation happens locally in your browser.

Space bar to regenerate

Click Generate or press Space
Bulk generation
x
Uses crypto.randomUUID() when available, falling back to crypto.getRandomValues(). Generated entirely in your browser. Nothing is stored or transmitted.

UUID v1 encodes a timestamp (current time) alongside random bits. It does not use a MAC address (for privacy). Each UUID is unique and time-ordered.

Click Generate

How to Use

1
Choose v4 or v1. Use v4 for most applications. Use v1 if you need time-sortable identifiers.
2
Select format. Standard (with hyphens) works for most uses. No hyphens is useful for database columns or URLs. Uppercase for environments that require it.
3
Generate and copy. Click on the UUID text to copy, or use the Copy button. Use bulk generation for database seeding or test data.

UUID v4 Structure

xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where y = 8, 9, a, or b (variant bits)

122 of the 128 bits are random. The remaining 6 bits encode the version (4) and variant. This gives 2^122 possible values, approximately 5.3 x 10^36.

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Frequently Asked Questions

What is a UUID?

UUID stands for Universally Unique Identifier. It is a 128-bit number formatted as 32 hex characters in the pattern xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. UUIDs are designed to be globally unique without requiring a central authority, making them ideal for distributed systems.

What is the difference between UUID v1 and v4?

UUID v4 uses cryptographically random bits and is the most common choice for new applications. UUID v1 incorporates the current timestamp and is time-sortable, useful for database performance. V4 is preferred for privacy since it reveals nothing about when or where it was generated.

Are UUIDs truly unique?

UUID v4 has 122 random bits, giving about 5.3 x 10^36 possible values. You would need to generate about 2.71 quintillion UUIDs to have a 50% chance of collision. In practice, this is impossible in any real application. UUIDs are safe to treat as unique.

When should I use UUIDs?

Use UUIDs for: database primary keys in distributed or multi-tenant systems, file names for user uploads, session tokens, request correlation IDs, and anywhere you need unique IDs that can be generated on the client side without a central counter. Avoid UUIDs when sequential IDs are important for performance (e.g., MySQL InnoDB clustering).

What is the format of a UUID?

Standard: xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx (36 chars including 4 hyphens). The M digit is the version (4 for v4). The N nibble is 8, 9, a, or b to indicate the RFC 4122 variant. Example: 550e8400-e29b-41d4-a716-446655440000.