UUID Generator — Generate UUIDs / GUIDs Online

Generate random v4 UUIDs (Universally Unique Identifiers) or GUIDs instantly. Generate up to 100 at once. All generated in your browser — none sent to any server.

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What Is a UUID?

A UUID (Universally Unique Identifier), also called a GUID (Globally Unique Identifier), is a 128-bit label used to identify information in computer systems. A standard UUID looks like 550e8400-e29b-41d4-a716-446655440000 — 32 hexadecimal digits in five groups separated by hyphens. The probability of generating a duplicate UUID is so low that UUIDs are considered practically unique across space and time without central coordination.

UUID v4 vs v1

UUID v4 is randomly generated using cryptographically secure random bytes. It is the most widely used version for general purposes because it has no correlation to time, machine, or environment. UUID v1 is generated using the current timestamp and MAC address. It is time-ordered (useful for database indexing) but leaks the generating machine's MAC address. For most applications — database primary keys, session tokens, file naming — v4 is preferred.

UUID vs GUID

UUID and GUID refer to the same concept. UUID (Universally Unique Identifier) is the RFC 4122 standard term used in Linux, databases, and most programming languages. GUID (Globally Unique Identifier) is Microsoft's terminology for the same format, used in Windows, .NET, and SQL Server. They are interchangeable — a GUID is a UUID in a different naming convention.

JavaScript: crypto.randomUUID() (modern browsers/Node.js 14.17+). Python: import uuid; uuid.uuid4(). Java: UUID.randomUUID(). Go: use github.com/google/uuid. PHP: Str::uuid() (Laravel) or ramsey/uuid.

Theoretically yes, but practically no. UUID v4 has 122 random bits — the probability of collision when generating 1 billion UUIDs per second for 100 years is about 50%. You would need to generate 2.71 quintillion UUIDs to have a 50% chance of a single collision.

The nil UUID is all zeros: 00000000-0000-0000-0000-000000000000. It is used as a null/empty value in systems that require a UUID type but want to indicate "no value."

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