Developer Tools
Create standards-compliant version 4 UUIDs using the browser Web Crypto API, with batch generation and one-click copying.
Settings
Simple workflow
How to use UUID Generator
- 1Choose how many UUIDs you need.
- 2Generate them securely in your browser.
- 3Copy an individual UUID or the complete list.
Good to know
Frequently asked questions
Is a UUID v4 guaranteed to be unique?
No mathematical guarantee is possible. A correctly generated UUIDv4 has 122 random bits, making accidental collisions extraordinarily unlikely, but systems should still enforce uniqueness when duplicates would cause harm.
How and where are the random UUIDs generated?
The browser uses crypto.getRandomValues() for 16 random bytes, then sets the RFC 9562 version and variant bits. Generated identifiers are not uploaded or stored by UtilSprout.
Practical guide
Create UUID version 4 identifiers with clear uniqueness boundaries
UUID Generator obtains 16 random bytes from the browser Web Crypto API, then sets the version field to 4 and the RFC 9562 variant field to binary 10. The resulting 128-bit value has 122 random bits and is displayed in the familiar 8-4-4-4-12 hexadecimal layout.
Version and variant bits describe how to interpret the identifier; they do not record a creation time, machine address or user identity. You can generate one UUID or a batch of up to 100 entirely in the current browser tab.
Worked example
Recognize the version and variant fields
- Start with
- Generate a UUID such as 919108f7-52d1-4320-9bac-f847db4148a8.
- Choose
- Read the first character of the third and fourth groups.
- You get
- The third group begins with 4 for UUIDv4. The fourth begins with 8, 9, a or b, which encodes the RFC variant's leading 10 bits. Every other displayed hex digit comes from random data.
Tips for a useful result
- Store UUIDs in a native UUID or fixed 16-byte database type when the system provides one, rather than assuming every textual format sorts the same way.
- Enforce a unique constraint when duplicates would damage data integrity, even though a collision from well-generated UUIDv4 values is extraordinarily unlikely.
- A UUID is an identifier, not proof of authorization. Do not grant access merely because a request contains a difficult-to-guess UUID.
Randomness, collisions and security
UUIDv4 has 122 random bits after reserving the version and variant fields. That makes accidental collisions impractical for ordinary application volumes, but it is a probability statement rather than a mathematical guarantee of uniqueness. A faulty random source, accidental reuse, copying or an import bug can also create duplicates independently of the ideal probability model.
The browser supplies the random bytes through crypto.getRandomValues(). Generated values are not saved by UtilSprout. Treat an exposed UUID like any other public record identifier: pair it with authentication and authorization when the referenced data is private.
Authoritative external sources
- RFC 9562: Universally Unique IDentifiers (external)
The current IETF UUID specification, including the UUIDv4 layout, version and variant fields, and random-data guidance.
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