UUID Generator

Generated UUID
Click "Generate UUID" to create a new UUID

Standard: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

Generated UUIDs

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UUID Generator creates Version 4 UUIDs based on random numbers

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What is a UUID?

A UUID (Universally Unique Identifier), also known as GUID (Globally Unique Identifier), is a 128-bit number used to identify information in computer systems. UUIDs are standardized by the Open Software Foundation (OSF) as part of the Distributed Computing Environment (DCE).

The primary purpose of UUIDs is to generate identifiers that have such a low probability of being duplicated that they can be considered unique for all practical purposes, even when generated on different systems without central coordination.

UUID Format

The canonical representation of a UUID uses 36 characters (32 hexadecimal digits and 4 hyphens):

xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

For example: 550e8400-e29b-41d4-a716-446655440000

UUID Versions

There are several versions of UUIDs, each generated differently:

  • Version 1: Generated from a timestamp and the MAC address of the computer
  • Version 2: Similar to version 1, but includes a local domain number
  • Version 3: Generated by hashing a namespace identifier and name (using MD5)
  • Version 4: Generated using random or pseudo-random numbers
  • Version 5: Similar to version 3, but using SHA-1 hashing

This tool generates Version 4 UUIDs, which are created using random or pseudo-random numbers. Version 4 UUIDs have the form: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where x is any hexadecimal digit and y is one of 8, 9, A, or B.

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Common Uses of UUIDs

UUIDs are widely used in software development and computer systems for various purposes:

1. Database Primary Keys

UUIDs can be used as primary keys in databases, especially in distributed systems where multiple servers might need to generate IDs without coordination.

2. Distributed Systems

In distributed systems, UUIDs help avoid conflicts when identifying resources across multiple systems or locations.

3. Session IDs

Web applications often use UUIDs to create unique session identifiers for users.

4. Transaction IDs

Financial and other transaction systems use UUIDs to uniquely identify each transaction.

5. Device and Application Identification

UUIDs can identify devices, applications, or components in larger systems.

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Advantages and Limitations of UUIDs

Advantages

  • No coordination needed: UUIDs can be generated independently without a central authority
  • Extremely low collision probability: The chance of generating duplicate UUIDs is negligible
  • Portable: UUIDs can be used across different systems and platforms
  • Privacy: Random UUIDs don't reveal system information (unlike MAC address-based UUIDs)
  • Scalability: Ideal for distributed and large-scale systems

Limitations

  • Size: 128 bits (16 bytes) is larger than sequential integer IDs
  • Database performance: Can be less efficient as indexes due to their random nature
  • Human readability: More difficult to read and communicate than simpler IDs
  • URL length: When used in URLs, they add considerable length
  • Sorting: Random UUIDs don't have meaningful sort order

Frequently Asked Questions

While it's theoretically possible for a UUID collision to occur, the probability is extremely low. Version 4 UUIDs have 122 random bits, giving approximately 5.3×10^36 possible values. To put this in perspective, you would need to generate about 2.71 quintillion UUIDs to have a 50% probability of a single collision.

Version 4 (random) UUIDs are the most widely used and recommended for most applications due to their simplicity and privacy benefits. Version 1 UUIDs might be preferred when timestamp ordering is important, but they expose MAC address information. Version 5 UUIDs are useful when you want deterministic IDs based on a namespace and name.

While UUIDs provide uniqueness, they are not designed specifically for security purposes. For authentication tokens or security-critical identifiers, consider using cryptographically secure random token generators or specific security libraries designed for authentication purposes.

  • JavaScript: crypto.randomUUID() or libraries like uuid
  • Python: import uuid; uuid.uuid4()
  • Java: java.util.UUID.randomUUID()
  • C#: System.Guid.NewGuid()
  • PHP: uuid_create() or ramsey/uuid library

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