UUID v4 Generator

A UUID (Universally Unique Identifier) is a 128-bit label used to identify objects in computer systems without requiring a central authority. UUIDs are standardized by RFC 4122 and typically written as 32 hexadecimal digits in the format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.

UUID v4 is generated from cryptographically secure random numbers. The version digit (position 13) is always 4, and the variant digit (position 17) is always 8, 9, a, or b. It's the most widely used UUID version for general-purpose identifiers.

UUID v4 uses 122 bits of randomness, yielding approximately 5.3 × 10³⁶ possible values. The probability of collision is negligible — you'd need to generate roughly 2.7 × 10¹⁸ UUIDs before a 50% chance of any collision. For all practical purposes, treat them as unique.

GUID (Globally Unique Identifier) is Microsoft's name for the same concept. GUIDs and UUIDs follow the same RFC 4122 standard and are completely interchangeable. The term "GUID" is more common in .NET and Windows ecosystems.

Yes — completely. All generation happens in your browser using the Web Crypto API (crypto.getRandomValues()). No data is sent to any server. The tool works fully offline once the page loads.

Some databases (MySQL, certain NoSQL stores) or systems prefer the compact 32-character hex string to save storage space or avoid parsing overhead. Toggle off hyphens to get the xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx format. Both represent the same identifier.

RFC 4122 specifies lowercase, but uppercase is often used in Windows/.NET environments (GUIDs) or to satisfy legacy system requirements. Uppercase and lowercase UUIDs are semantically identical — they represent the same value.

Yes. UUID v4 is a popular choice for distributed systems where you need globally unique IDs without a central counter. For high-insert-rate relational databases, consider UUID v7 (time-ordered) to avoid index fragmentation, but v4 works fine for most use cases.