A UUID (Universally Unique Identifier) is a 128-bit identifier that is guaranteed to be unique across space and time. UUIDs are commonly used as database primary keys, API identifiers, session tokens, and distributed system identifiers.

What is the difference between UUID v4 and v1?

UUID v4 is randomly generated, making it the most common choice for general-purpose unique IDs. UUID v1 is time-based and includes the MAC address of the generating machine. UUID v7 is a newer time-ordered format that is database-friendly.

Are UUIDs guaranteed to be unique?

For all practical purposes, yes. The probability of generating two identical UUID v4 values is approximately 1 in 5.3 x 10^36 — effectively zero. You would need to generate 1 billion UUIDs per second for 85 years to have a 50% chance of one collision.

Can I generate UUIDs without dashes?

Yes. This tool lets you toggle between standard format (with dashes) and compact format (without dashes). You can also choose uppercase or lowercase output.

UUID Generator

Generate UUIDs (GUIDs) instantly — v4, v1, v7, bulk, and custom formats

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UUID Validator & Parser

UUID Versions

v4 Random — most common. Best for general-purpose unique IDs.
v1 Timestamp + MAC address. Useful for debugging & ordering.
v7 Time-ordered random. Best for database primary keys (sortable).

Quick Tips

Click the UUID to copy it instantly
Use v7 for database primary keys (time-sortable)
Use compact format for URL-safe IDs
Generate up to 500 UUIDs at once

UUID Anatomy

xxxxxxxx-xxxx-4xxx-axxx-xxxxxxxxxxxx

4 = version number
a = variant (8, 9, a, or b)
Total: 128 bits / 32 hex chars

100% Private

All UUIDs are generated locally in your browser using the Web Crypto API. Nothing is sent to any server.

What Is a UUID?

Understanding Universally Unique Identifiers and why they matter

A UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 9562. UUIDs are designed to be globally unique without requiring a central authority — any system can generate one independently with virtually zero chance of collision.

UUIDs are widely used as database primary keys, API resource identifiers, session tokens, file names, distributed system identifiers, and message queue IDs. The format consists of 32 hexadecimal characters displayed in five groups separated by hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.

A GUID (Globally Unique Identifier) is Microsoft's term for the same concept. The terms UUID and GUID are completely interchangeable — they refer to identical data structures and generation algorithms.

Database Keys

UUIDs are perfect primary keys for distributed databases where auto-increment IDs cause conflicts. UUID v7 is sortable, making it ideal for clustered indexes.

API Resources

Exposing sequential IDs in APIs is a security risk. UUIDs make resource identifiers unpredictable and safe to share in URLs without revealing system internals.

Distributed Systems

In microservices and event-driven architectures, UUIDs allow any service to create unique IDs independently without coordination or central registries.

UUID Version Comparison

Choose the right UUID version for your use case

Feature	v1	v4	v7
Source	Timestamp + MAC	Random	Timestamp + Random
Sortable	Partially	No	Yes
Privacy	Leaks MAC address	Fully private	Fully private
Collision risk	Very low	Extremely low	Extremely low
DB performance	Good	Poor (random I/O)	Excellent (sequential)
Best for	Legacy systems	General purpose	Modern databases

Frequently Asked Questions

Common questions about UUIDs and GUIDs

A UUID (Universally Unique Identifier) is a 128-bit identifier formatted as 32 hexadecimal characters in five groups: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. UUIDs are designed to be globally unique without a central authority, making them ideal for distributed systems, databases, and APIs.

UUID v4 is entirely randomly generated, making it the most common and recommended version for general use. UUID v1 combines a timestamp with the machine's MAC address, which means it encodes when and where it was created — useful for debugging but a potential privacy concern.

For all practical purposes, yes. A UUID v4 has 122 random bits, giving 5.3 × 10³⁶ possible values. To reach a 50% collision probability, you would need to generate approximately 2.71 × 10¹⁸ UUIDs — equivalent to generating 1 billion UUIDs per second for 85 years.

GUID (Globally Unique Identifier) is Microsoft's term for UUID. They are functionally identical — a GUID follows the same RFC standard as UUID. The terms are completely interchangeable in all contexts.

Use UUID v7 when you need time-ordered unique IDs, especially for database primary keys. Unlike v4 (random), v7 UUIDs are sortable by creation time, which dramatically improves B-tree index performance in databases like PostgreSQL, MySQL, and MongoDB.

Yes. Use the Format dropdown to switch between standard (with dashes), compact (no dashes), braces (for .NET/Windows), or URN format. You can also toggle between lowercase and UPPERCASE output.