What is the chance of two UUID v4 values colliding?

The collision probability is approximately 1 in 2^122. You would need to generate one billion UUIDs every second for about 85 years to have a 50% probability of a single collision.

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UUID / GUID Generator

Generate version 4 UUIDs (Universally Unique Identifiers) individually or in batches up to 500. Customize uppercase/lowercase and include or remove hyphens.

Quantity:(Max 100)

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Generated UUIDs (0)

About & How It Works

Technical calculation logic, standards, and operational details

The UUID Generator creates cryptographically secure Universally Unique Identifiers (UUID v4) compliant with RFC 4122. UUIDs provide 128 bits of uniqueness, meaning the probability of generating a duplicate UUID is so infinitesimally low that it is practically zero across the lifetime of the universe. It is widely used in distributed software architectures, database primary keys, and transaction tracing.

Algorithmic Logic & Calculation

Our generator uses the browser's native Web Cryptography API (`crypto.getRandomValues()`) to seed true hardware-level entropy into 16 random bytes. It sets the version bits (0100 for version 4) and variant bits (10 for RFC 4122), formatting the output into the canonical 8-4-4-4-12 hexadecimal character representation.

Technical Standards & Compliance

Strictly complies with IETF RFC 4122 Section 4.4 and W3C Web Cryptography API recommendations.

Key Features & Capabilities

RFC 4122 Version 4 Compliant

Generates standard-compliant random UUIDs with correct variant and version bits.

Cryptographically Secure Entropy

Uses OS-level Web Cryptography API rather than predictable Math.random().

Bulk Generation Capabilities

Generate 1, 5, 10, or up to 100 unique UUIDs at once for seed scripts.

Uppercase & Hyphen Customization

Toggle between lowercase, uppercase, and hyphen-free raw string formats.

Practical Real-World Use Cases

Database Primary Keys & Distributed IDs

Generate conflict-free primary keys across distributed PostgreSQL, MongoDB, or MySQL clusters.

Software Testing & Mocking

Create fixture data and mock user IDs for automated integration tests and unit suites.

Session & Tracking Identifiers

Generate unique correlation IDs for API request tracing and telemetry logs.

How to Use

Select the quantity of UUIDs to generate (1 to 500).
Choose options (uppercase, no hyphens).
Click Generate and copy all or individual UUIDs.

In-Depth Educational Guide

Client-Side Security Guide: Why In-Browser Tools Protect Your Sensitive Data

Learn how modern WebAssembly and JavaScript enable private, 100% in-browser utilities that guarantee zero data leakage, ideal for API keys, JSON payloads, and sensitive tokens.

Read Full Guide