Free UUID v4 Generator — Create Random Unique Identifiers Online

What Is a UUID v4?

A UUID (Universally Unique Identifier) is a 128-bit identifier that is guaranteed to be unique across all devices and time. UUID version 4 generates identifiers using random or pseudo-random numbers, making them virtually impossible to duplicate — the probability of generating two identical UUIDs is astronomically low (1 in 2¹²²).

A typical UUID v4 looks like this: 550e8400-e29b-41d4-a716-446655440000 — 32 hexadecimal digits displayed in five groups separated by hyphens.

Why Use UUIDs?

UUIDs solve a fundamental problem in software development — how to create unique identifiers without a central authority or database coordination. Here's why they matter:

• Database primary keys — UUIDs eliminate the risk of ID collisions in distributed databases
• Distributed systems — Multiple servers can generate IDs independently without conflicts
• API integrations — UUIDs provide consistent identifiers across different systems and services
• Security — Unlike sequential IDs, UUIDs don't reveal information about record count or creation order
• Merge-friendly — When combining data from multiple sources, UUID keys never clash

How to Use the UUID v4 Generator

1. Open the UUID v4 Generator tool on this page
2. Select how many UUIDs you need to generate
3. Click Generate to create your unique identifiers
4. Copy the results — each UUID is ready to use in your application
5. Generate as many as you need — each one is guaranteed to be unique

UUID v4 Format Explained

Every UUID v4 follows the pattern: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx

• x — Any hexadecimal digit (0–9, a–f)
• 4 — Always "4" in the third group, indicating version 4
• y — One of 8, 9, a, or b — indicating the UUID variant

Common Use Cases

• Database records — Using UUIDs as primary keys in PostgreSQL, MySQL, MongoDB, and other databases
• Session management — Generating unique session tokens for web applications
• File naming — Creating unique filenames to prevent overwrites in storage systems
• Message queues — Assigning unique IDs to messages in systems like RabbitMQ or Kafka
• Testing — Generating unique test data for development and QA environments
• Tracking pixels — Creating unique identifiers for analytics and conversion tracking

Best Practices

• Store as 36 characters — Include the hyphens for readability, or store as 32 hex characters to save space
• Use lowercase — While UUIDs are case-insensitive, lowercase is the standard convention
• Index properly — When using UUIDs as database keys, ensure proper indexing for query performance
• Consider UUID v7 for sorted data — If you need time-sortable IDs, UUID v7 is a newer alternative
• Don't use for security tokens — UUIDs are unique but not cryptographically secure; use proper CSPRNG for security tokens

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Frequently Asked Questions

Can two UUID v4 values ever be the same?

Theoretically yes, but practically no. With 2¹²² possible values (over 5.3 × 10³⁶), the probability of a collision is vanishingly small. You would need to generate approximately 2.71 × 10¹⁸ UUIDs to have a 50% chance of a single duplicate.

What is the difference between UUID and GUID?

GUID (Globally Unique Identifier) is Microsoft's implementation of the UUID standard. They are functionally identical — GUID is simply the term used in Microsoft ecosystems (.NET, SQL Server), while UUID is the universal standard (RFC 4122).

Should I use UUID v4 or auto-increment IDs?

Use auto-increment IDs for simple, single-database applications where performance is critical. Use UUID v4 for distributed systems, microservices, or when you need IDs generated before database insertion. UUIDs add slight storage overhead but provide much greater flexibility.

Are UUIDs secure enough for API keys?

UUIDs are unique but not designed for security purposes. For API keys and authentication tokens, use a cryptographically secure random generator (CSPRNG) instead. UUIDs can be used as non-sensitive identifiers, but never as secrets.