Free Online UUID Generator

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit identifier designed to be unique across all systems, devices, and time without requiring a central registration authority. The concept was originally created for the Apollo Network Computing System and was later standardized by the International Organization for Standardization (ISO) and the Internet Engineering Task Force (IETF).

UUIDs are also commonly known as GUIDs (Globally Unique Identifiers) in Microsoft ecosystems. While technically the same, the term GUID is predominantly used in Windows development, .NET applications, and Microsoft SQL Server, whereas UUID is the standard term used in most other programming languages and databases. Our GUID generator produces the same output but formatted for Microsoft conventions.

Standard UUID Format

A UUID is represented as a 36-character string consisting of 32 hexadecimal digits displayed in five groups separated by hyphens:

Where:

• x represents a hexadecimal digit (0-9, a-f)
• M indicates the UUID version (1-7)
• N indicates the variant (typically 8, 9, a, or b for RFC 4122 compliant UUIDs)

Example of a valid UUID v4:

Understanding UUID Structure

A UUID consists of 128 bits (16 bytes) of data. When represented as a string, it breaks down into five distinct sections, each serving a specific purpose depending on the UUID version:

How to Identify UUID Version

You can identify a UUID's version by looking at the 13th character (the first digit of the third group). For example:

• 550e8400-e29b-11d4-a716-446655440000 — Version 1 (timestamp)
• 550e8400-e29b-41d4-a716-446655440000 — Version 4 (random)
• 550e8400-e29b-71d4-a716-446655440000 — Version 7 (Unix timestamp)

Use our UUID Decoder tool to automatically parse and analyze any UUID, extracting its version, variant, and embedded timestamp information.

UUID Versions Explained

There are several UUID versions defined by RFC 4122 and the newer RFC 9562. Each version has different characteristics and use cases. Our online UUID generator supports the most commonly used versions.

How Unique is a UUID? Understanding Collision Probability

One of the most common questions about UUIDs is: "How unique are they really?" The answer lies in mathematics and probability theory. UUIDs are designed to be practically unique without coordination between generating parties.

The Mathematics of UUID Uniqueness

For UUID v4 (random), which uses 122 random bits (the remaining 6 bits are used for version and variant), the total number of possible UUIDs is:

Birthday Paradox and Collision Probability

The probability of UUID collision follows the birthday paradox. To have a 50% chance of at least one collision, you would need to generate approximately:

Real-World Perspective

To put this astronomical number into perspective:

• Time perspective: If you generated 1 billion UUIDs per second continuously, it would take approximately 86 years to have a 50% chance of generating just one duplicate.
• Global scale: If every human on Earth (8 billion people) each generated 600 million UUIDs, there would still only be a 50% probability of one collision occurring somewhere.
• Internet scale: If every web request on the entire internet was assigned a UUID (approximately 5 billion requests per day), it would take over 1 million years to reach 50% collision probability.
• Storage perspective: Storing 2.71 quintillion UUIDs would require approximately 43 exabytes of storage space—more than all the data centers of major tech companies combined.

Collision Probability Table

This makes UUIDs suitable for virtually any application requiring unique identifiers without central coordination. Learn how to generate UUIDs in your preferred programming language: Python, JavaScript, Java, Go, or explore our bulk generator for generating thousands of UUIDs at once.

Common Use Cases for UUIDs

UUIDs have become an essential tool in modern software development. Here are the most common scenarios where UUIDs provide significant benefits:

UUID vs Auto-Increment IDs: A Detailed Comparison

Choosing between UUIDs and auto-increment integers for database primary keys is one of the most debated topics in software architecture. Here's a comprehensive comparison to help you make the right choice.

When to Use UUIDs

• Distributed databases — When running multiple database nodes that need to generate IDs independently
• Microservices architecture — When services create records without database access
• Data synchronization — When merging data from multiple sources (mobile offline sync, multi-tenant apps)
• Security-sensitive applications — When IDs should not be guessable (user profiles, documents)
• Public APIs — When IDs are exposed in URLs and shouldn't reveal business information

When to Use Auto-Increment

• Simple applications — Single database, single server, internal tools
• High-volume logging — Where storage efficiency is critical
• Legacy system integration — When existing systems expect integer IDs
• Human-facing references — Order numbers, ticket IDs that users need to reference verbally

Why Use Our Online UUID Generator?

Our free UUID generator tool at onlineuuidgenerator.pages.dev is designed with developers in mind, offering a combination of security, speed, and convenience that sets it apart.

Generate UUIDs in Your Programming Language

Need to generate UUIDs programmatically? We provide comprehensive guides with code examples for all major programming languages:

Quick Code Examples

Here are quick examples for the most popular languages:

import uuid

# Generate UUID v4 (random)
my_uuid = uuid.uuid4()
print(my_uuid)  # e.g., 550e8400-e29b-41d4-a716-446655440000

// Modern browsers (Chrome 92+, Firefox 95+, Safari 15.4+)
const uuid = crypto.randomUUID();
console.log(uuid);  // e.g., 550e8400-e29b-41d4-a716-446655440000

import java.util.UUID;

UUID uuid = UUID.randomUUID();
System.out.println(uuid);  // e.g., 550e8400-e29b-41d4-a716-446655440000

UUID in Databases

Using UUIDs as primary keys in databases requires proper configuration for optimal performance. We provide detailed guides for all major database systems:

UUID Standards & Specifications

UUIDs are defined by internationally recognized standards, ensuring interoperability across systems and programming languages:

Frequently Asked Questions