UUID v4 & UUID Generator Online - Cryptographically Random RFC 9562 Identifiers
Generate cryptographically random UUID v4 (RFC 9562 / RFC 4122) identifiers in single or bulk batches right in your browser, for collision-free database primary keys and idempotency tokens.
Runs in your browser
This tool processes your input on your device.
Developer tools
Loading tool…
Processed in your browserTry another tool
Instructions
How to use it
Follow these steps in the workspace above.
- Choose how many UUIDs you need (from 1 to bulk batches) and select your formatting preference.
- Click Generate to mint fresh 128-bit cryptographically random UUIDs in your browser.
- Copy an individual UUID or the entire batch list for SQL migrations, JSON fixtures, or API test payloads.
Guide
How it works
A Universally Unique Identifier (UUID), standardized in RFC 9562 (which updated RFC 4122), is a 128-bit number formatted as 36 characters in an 8-4-4-4-12 hexadecimal layout (for example, 550e8400-e29b-41d4-a716-446655440000). Because UUIDs can be generated independently across distributed microservices, mobile clients, and edge workers without coordinating with a central database sequence, they prevent primary-key collisions.
Anatomy of a Version 4 UUID
- 122 Bits of Random Entropy: In a Version 4 UUID, the third group starts with 4 (identifying version 4) and the fourth group starts with 8, 9, a, or b (identifying the RFC variant), leaving 122 random bits.
- Astronomically Low Collision Risk: With 5.3 undecillion possible values, you would need to generate 1 billion UUIDs per second for 85 years to reach a 50% probability of a single collision.
- Browser WebCrypto Generation: Generated locally via the browser native
crypto.randomUUID()API.
Yes. Every UUID is generated inside your browser using the Web Cryptography API and is never logged or transmitted to any server.
Per RFC 9562 / RFC 4122, bits 48 through 51 of the 128-bit structure encode the 4-bit version number (0100 in binary = 4 in hex), allowing parsers to verify it is a random v4 UUID.
Always prefer PostgreSQL’s native UUID type (16 bytes) or MySQL’s BINARY(16) over VARCHAR(36) to cut index storage by more than 50% and speed up B-tree joins.
