Random GUID Generator | Free UUID v4 Generator Online

A GUID (Globally Unique Identifier) is a 128-bit integer used as a unique identifier in software development. The probability of generating duplicate GUIDs is so low that they are considered practically unique across all space and time.

GUID Versions Explained

UUID v4 (Random)

The most common version. All bits except the version and variant are randomly generated. Provides approximately 122 bits of entropy, making collisions astronomically unlikely.

Example: 550e8400-e29b-41d4-a716-446655440000

UUID v1 (Time-based)

Combines timestamp with node information (usually MAC address). Sortable by creation time, useful for database indexing and chronological ordering.

Example: c7b7d5b0-5a1a-11ec-90d6-0242ac120003

Cryptographic Secure

Uses the browser's Crypto API for true randomness. Essential for security-sensitive applications like session tokens, API keys, and password salts.

Source: window.crypto.getRandomValues()

Nil UUID

The special "zero" UUID (all bits set to 0). Used as a placeholder, null value, or to indicate "no UUID" in databases and protocols.

Format: 00000000-0000-0000-0000-000000000000

Common Use Cases

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Database Primary Keys

Use GUIDs as primary keys to avoid ID conflicts when merging databases or working in distributed systems.

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API Keys & Tokens

Generate secure, unpredictable tokens for API authentication and session management.

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File Identifiers

Assign unique IDs to files, documents, and assets in content management systems.

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Distributed Systems

Create identifiers that remain unique across multiple servers without coordination.

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Order Numbers

Generate unique order IDs that don't reveal business information or order volume.

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Device IDs

Identify devices, installations, or user sessions in mobile and web applications.

Technical Specifications

Property	Value	Description
Size	128 bits (16 bytes)	Fixed length across all versions
String Format	32 hex digits + 4 hyphens	8-4-4-4-12 grouping
Total Combinations	2¹²⁸ (3.4 × 10³⁸)	More than atoms in the universe
Variant Bits	2 bits (position 8)	Indicates layout variant (usually 10xx)
Version Bits	4 bits (position 6)	Identifies generation method (v1-v5)

Collision Probability

The probability of generating duplicate UUID v4 is extremely low. Here's what that means in practical terms:

• To have a 50% chance of a single collision, you'd need to generate about 2.7 quintillion UUIDs
• If you generated 1 billion UUIDs per second, it would take 85 years to reach a 50% collision probability
• The number of possible UUIDs (3.4×10³⁸) is larger than the number of stars in the observable universe
• You're more likely to be struck by lightning twice in the same day than to generate a duplicate UUID v4

GUID vs UUID

GUID (Microsoft)

• Term used primarily in Microsoft technologies
• Often includes braces in string representation
• May use mixed case by default
• Common in Windows, .NET, COM programming

UUID (RFC 4122)

• Standardized format (RFC 4122)
• Usually lowercase without braces
• Widely used across all platforms
• Common in Linux, Unix, open source

🔒 Security Note

For security-critical applications (API keys, session tokens, password salts), use the Secure (Crypto) version. It uses the browser's cryptographically secure random number generator, which is designed to be unpredictable and suitable for security purposes.

🔑 Random GUID Generator

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Understanding GUIDs (Globally Unique Identifiers)