UUID v4 generator

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About UUID v4 Generator

UUID v4 Generator produces version-4 universally unique identifiers. It uses cryptographically secure randomness so collisions are astronomically unlikely.

How to use it

Pick how many UUIDs to generate. The list is ready to copy or download.

Common use cases

Generating primary keys. Tracking anonymous users. Building request IDs.

What is a UUID v4?

A UUID (Universally Unique IDentifier) is a 128-bit number formatted as 36 characters in the canonical form 8-4-4-4-12, such as 123e4567-e89b-42d3-a456-426614174000. A version 4 UUID is generated from random or pseudo-random data rather than from a timestamp or MAC address, which makes it statistically safe to create many of them with a vanishingly small chance of collision. The version is indicated by the fourth block starting with a 4, and the variant by the fifth block beginning with 8, 9, A or B, exactly as this tool produces.

How to Use the UUID v4 Generator

Open the tool and a fresh random UUID v4 is generated automatically. Use the options to copy it to the clipboard, switch between uppercase and lowercase, and include or remove the separating hyphens for the compact 32-character form. Each time you press the Generate button a new value is created from the random source, so every identifier is independent of the last. Paste the result directly into your code, database or configuration.

Common Use Cases

Developers use UUIDs as primary keys in databases and as identifiers in distributed systems where a single auto-increment counter cannot be shared safely. They serve as request and trace IDs in logs, as tokens for public API resources, and as filenames for uploaded files where collisions would overwrite data. Because a UUID carries no sequential information, it also avoids leaking the volume of records in a system.

Limitations

A UUID v4 relies on the quality of the random source: on the web it draws from the browser's cryptographically secure random number generator, which is strong. Mathematically the collision risk is minuscule, but it is not zero; UUIDs are not guarantees. And because they are random, databases should use a UUID-aware generation strategy to avoid index fragmentation from non-sequential keys.

Frequently asked questions

What does the 4 in the version block mean?

The 4 in the third group of a UUID v4 indicates the version, which is the random-based scheme. That digit is fixed for all v4 UUIDs, and tools that validate UUIDs check it to confirm the version.

Is it safe to use UUIDs as database primary keys?

Yes, UUIDs are safe and common as primary keys, especially in distributed or merged systems. One trade-off is that random UUIDs are not sequential, which can fragment B-tree indexes, so many databases offer a storage-optimized or version 7 time-ordered scheme when ordering matters.

What is the difference between UUID with and without hyphens?

The canonical form includes hyphens for readability (36 characters); removing them yields the compact 32-character form with the same value. Both represent the identical identifier, and many systems accept either format.