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UUID Generator

Generate unique identifiers (UUID/GUID) for your applications instantly

UUID Version

Format Options

Bulk Generation

UUID Version Comparison

Version Method Sortable Best For
v1 Timestamp + MAC address Partial Legacy systems, debugging
v4 Random No General purpose, security
v7 Unix timestamp + random Yes Database keys, distributed systems

UUID Format Examples

Standard 550e8400-e29b-41d4-a716-446655440000
Uppercase 550E8400-E29B-41D4-A716-446655440000
No Hyphens 550e8400e29b41d4a716446655440000
Braces (GUID) {550e8400-e29b-41d4-a716-446655440000}

Understanding UUIDs for Software Development

Universally Unique Identifiers (UUIDs) serve as fundamental building blocks for modern software architecture, providing collision-resistant identifiers for databases, distributed systems, and API resources. Our free UUID generator creates standards-compliant identifiers using cryptographically secure randomness, supporting multiple versions and formats for diverse development requirements.

UUID v4: The Random Standard

UUID version 4 generates identifiers using 122 bits of cryptographic randomness, making it the most widely adopted version for general-purpose use. The astronomical number of possible combinations (over 5 undecillion) makes collision probability negligible for any practical application. Major platforms including PostgreSQL, MongoDB, and AWS use v4 as their default UUID implementation.

UUID v1: Timestamp-Based Identification

Version 1 UUIDs embed a 60-bit timestamp and 48-bit node identifier (typically MAC address) enabling temporal ordering and origin tracing. While useful for debugging and audit trails, v1 UUIDs expose hardware identifiers raising privacy concerns for public-facing applications. The timestamp resolution reaches 100-nanosecond intervals, supporting high-frequency generation scenarios.

UUID v7: Modern Time-Ordered Identifiers

The newest UUID version combines Unix millisecond timestamps with random data, providing natural chronological sorting without exposing hardware identifiers. Database indexes benefit significantly from v7's time-ordering, reducing fragmentation and improving query performance for time-series data. UUID v7 represents the recommended choice for new database primary keys requiring sortability.

Database Primary Keys and Indexing

UUIDs as primary keys enable horizontal scaling, offline ID generation, and entity merging across distributed databases. However, random v4 UUIDs cause index fragmentation in B-tree structures. Time-ordered v7 UUIDs maintain sequential insertion patterns preserving index efficiency while retaining UUID benefits. Consider your access patterns when selecting UUID versions for database schemas.

API Resource Identification

RESTful APIs benefit from UUID resource identifiers over sequential integers by preventing enumeration attacks and enabling decentralized ID generation. Clients can generate valid resource IDs before server communication, supporting optimistic UI patterns and offline-first architectures. The 36-character standard format integrates seamlessly with URL paths and JSON payloads.

Security and Privacy Considerations

UUID v4 provides no information leakage, making it suitable for security-sensitive contexts like session tokens and access keys. Avoid v1 UUIDs in public interfaces as MAC addresses can identify hardware and approximate generation times. All UUIDs generated here use the Web Crypto API (crypto.getRandomValues), ensuring cryptographic-quality randomness for security applications.

$ faq

What is a UUID? ▸
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 standard format is 8-4-4-4-12 hexadecimal digits separated by hyphens (e.g., 550e8400-e29b-41d4-a716-446655440000).
What is the difference between UUID and GUID? ▸
UUID and GUID (Globally Unique Identifier) are essentially the same thing. UUID is the term used in most contexts and defined by RFC 4122, while GUID is Microsoft's implementation and terminology. Both use the same 128-bit format and serve identical purposes for unique identification.
What UUID versions are available? ▸
This generator supports UUID v1 (timestamp-based using MAC address), UUID v4 (random), and UUID v7 (timestamp-ordered with random). V4 is most common for general use due to its simplicity and randomness. V1 provides time-ordering but exposes MAC address. V7 is the newest standard combining timestamp ordering with privacy.
Which UUID version should I use? ▸
UUID v4 is recommended for most applications due to its simplicity and strong randomness. Use UUID v1 when you need timestamp information embedded. UUID v7 is ideal for database primary keys as it provides time-ordering for better index performance while maintaining privacy unlike v1.
How random is UUID v4? ▸
UUID v4 contains 122 random bits (6 bits are fixed for version and variant). This provides approximately 5.3×10^36 possible combinations. The probability of generating duplicate UUIDs is astronomically low—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 in bulk? ▸
Yes, you can generate up to 1000 UUIDs at once. Simply set your desired quantity, choose the UUID version and format options, then generate. Results can be copied to clipboard or downloaded as a text file for easy integration into databases, configuration files, or test data.
Are the generated UUIDs truly unique? ▸
Yes, UUIDs generated here use cryptographically secure random number generation (crypto.getRandomValues) in your browser. The mathematical probability of collision is negligible for practical purposes. All generation happens client-side, ensuring your UUIDs are never transmitted or stored externally.