UUID Generator

How to Use the UUID Generator

This free online UUID generator creates version 4 universally unique identifiers (UUIDs) directly in your browser. UUID v4 identifiers are generated using cryptographically secure random numbers via the Web Crypto API, ensuring high-quality randomness. Simply specify the number of UUIDs you need (from 1 to 100), click the generate button, and copy individual UUIDs or all of them at once. No data is sent to any external server.

What Is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 4122. UUIDs are designed to be unique across space and time without requiring a central registration authority. The version 4 UUID format uses random or pseudo-random numbers for all significant bits, making collisions extremely unlikely. The probability of generating two identical UUID v4 values is approximately 1 in 2^122, which is for all practical purposes zero. UUIDs are represented as 32 hexadecimal digits displayed in five groups separated by hyphens in the form 8-4-4-4-12.

Common Use Cases for UUIDs

UUIDs are widely used in software development as primary keys in databases, ensuring unique record identification without sequential counters that could expose business data. They serve as correlation identifiers in distributed systems and microservice architectures, allowing requests to be traced across multiple services. UUIDs are also used as session tokens, file identifiers, message IDs in event-driven systems, and unique resource names in cloud infrastructure. Their guarantee of uniqueness without coordination makes them ideal for systems where multiple components generate identifiers independently.

UUID v4 vs Other Versions

While UUID v1 uses timestamps and MAC addresses, and UUID v5 uses namespace-based hashing, UUID v4 relies entirely on random numbers. This makes v4 the most commonly used version for general-purpose unique identifier generation because it requires no external input and provides strong uniqueness guarantees. Some newer proposals like UUID v7 combine timestamps with randomness for sortable identifiers, but v4 remains the standard choice for most applications.

UUIDジェネレーターの使い方

この無料オンラインUUIDジェネレーターは、ブラウザ内でUUID v4を即座に生成します。 Web Crypto APIを使用した暗号学的に安全な乱数で生成されるため、高品質な一意性が保証されます。 生成数(1～100)を指定し、「生成」ボタンをクリックするだけです。 個別にコピーすることも、「全てコピー」で一括コピーすることもできます。 データはサーバーに送信されることなく、全てブラウザ内で処理されます。