UUID Generator

What is a UUID (or GUID)?

A UUID (Universally Unique Identifier), also known as a GUID (Globally Unique Identifier) in Microsoft and Windows environments, is a 128-bit identifier that is unique across both space and time. UUIDs and GUIDs are the same thing — just different names used by different ecosystems. They are standardized by RFC 4122 and are widely used in software development to uniquely identify objects, records, sessions, and resources without requiring a central authority to coordinate ID generation.

How to Generate a Random UUID v4

This tool generates Version 4 UUIDs (random UUIDs), which are created using cryptographically secure random numbers. A v4 UUID has the format xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where x is a random hexadecimal digit and y is one of 8, 9, a, or b. The "4" in the third group indicates the UUID version. With 122 random bits, the probability of generating a duplicate UUID is astronomically low (about 1 in 2.7 quintillion). Click "Generate New UUID" to create one instantly, or use bulk generation to create up to 100 random GUIDs at once.

Common Use Cases for UUIDs and GUIDs

UUIDs and GUIDs are used as database primary keys, API request identifiers, session tokens, distributed system node identifiers, file and resource naming, message queue correlation IDs, and cache keys. They are especially valuable in distributed systems where multiple nodes need to independently generate unique identifiers without coordination. Common ecosystems: PostgreSQL UUID column type, MongoDB ObjectIds (similar concept), .NET Guid struct, Java UUID class, Python uuid module, JavaScript crypto.randomUUID(). This generator uses the Web Crypto API for cryptographically secure random number generation.

Frequently Asked Questions

What is the difference between UUID and GUID?

UUID (Universally Unique Identifier) and GUID (Globally Unique Identifier) refer to the same concept — a 128-bit identifier guaranteed to be unique across systems. "UUID" is the term used in RFC 4122 and the Linux/open source world; "GUID" is the term Microsoft uses in Windows, .NET, and SQL Server. Both have the same format and you can use them interchangeably.

Is this UUID generator cryptographically secure?

Yes. This generator uses the browser's built-in Web Crypto API (crypto.getRandomValues), which provides cryptographically secure random number generation suitable for security-sensitive uses like session tokens, password reset links, and API keys.

Why use UUID v4 over other versions?

UUID v4 is the most commonly used version because it requires no coordination and exposes no system information. Other versions: v1 uses MAC address + timestamp (predictable, leaks identity), v3/v5 use namespace hashing (deterministic), v7 is timestamp-based with random suffix (sortable). For most applications, v4's pure randomness is the right choice.

Are my generated UUIDs private?

Yes. All UUIDs are generated locally in your browser using the Web Crypto API. Nothing is sent to any server. The page works offline once loaded.