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Free Online UUID Generator

Generate secure, random UUIDs (v4) instantly in your browser.

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Understanding UUIDs

A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. The probability that a UUID will be duplicated is not zero, but it is close enough to zero to be negligible.

UUIDs are standardized by the Open Software Foundation (OSF) as part of the Distributed Computing Environment (DCE). They are also documented in RFC 4122.

UUID Structure

A standard UUID is a 32-character hexadecimal string, displayed in five groups separated by hyphens, in the form 8-4-4-4-12 for a total of 36 characters (32 alphanumeric characters and 4 hyphens).

xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx
  • The M position indicates the UUID version (for v4, this is always '4').
  • The N position indicates the variant (for v4, this is one of '8', '9', 'a', or 'b').

Why Use Version 4?

Version 4 UUIDs are completely random. Unlike Version 1 (which includes a timestamp and MAC address), v4 UUIDs do not reveal any information about the time they were created or the machine that created them. This makes them ideal for:

  • Privacy: No hardware address or timestamp is encoded.
  • Simplicity: Can be generated anywhere without coordination.
  • Performance: Fast to generate with modern cryptographic libraries.

Common Use Cases

  • Database Keys: Primary keys in distributed databases (like Cassandra or DynamoDB) or when using ORMs.
  • Session IDs: Unique tokens for user sessions in web applications.
  • File Names: Preventing filename collisions in uploaded files.
  • API Keys: Generating unique access tokens (though specialized formats are often preferred).
  • Transaction IDs: Tracking requests across microservices.

Frequently Asked Questions

What is a UUID?

UUID stands for Universally Unique Identifier. It is a 128-bit label used for information in computer systems. The term GUID (Globally Unique Identifier) is also used, typically in Microsoft technologies.

Are generated UUIDs truly unique?

For all practical purposes, yes. The probability of a collision (generating the same UUID twice) is so astronomically low that it can be ignored for most applications. A collision would require generating billions of UUIDs per second for years.

Which UUID version does this tool generate?

This tool generates Version 4 (random) UUIDs, which are created using random numbers. This is the most common version used in modern applications.

Can I use these UUIDs for database primary keys?

Yes, UUIDs are excellent for primary keys in distributed systems where you need to generate IDs without checking a central database. They prevent ID conflicts when merging data from different sources.

Is the generation secure?

Yes. This tool uses the browser's cryptographic API (crypto.randomUUID) to generate cryptographically strong random values locally on your device. No data is sent to any server.

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