UUID Generator

Generate UUIDs (Universally Unique Identifiers) v4 instantly with bulk generation support

Generate UUIDs

Create random version 4 UUIDs for your applications

Number of UUIDs

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. Also known as GUID (Globally Unique Identifier) in Microsoft systems, UUIDs are standardized by the Open Software Foundation (OSF) as part of the Distributed Computing Environment (DCE). UUIDs are displayed as 32 hexadecimal digits in groups of 8-4-4-4-12, like: 550e8400-e29b-41d4-a716-446655440000.

UUID Version 4

Version 4 UUIDs are randomly generated. Out of 128 bits, 122 bits are random, while 6 bits are fixed to indicate the version and variant. This provides 2^122 (about 5.3 × 10^36) possible UUIDs, making collisions astronomically unlikely. V4 is the most commonly used UUID version because it's simple, requires no coordination between systems, and has excellent uniqueness guarantees.

Common Use Cases

Database Primary Keys

Use UUIDs as primary keys in distributed databases where auto-incrementing IDs won't work. UUIDs can be generated on any server without coordination, preventing conflicts in multi-master replication systems.

Session & Request IDs

Track user sessions, HTTP requests, and transactions across microservices. UUIDs help correlate logs and debug distributed systems by providing unique identifiers that span multiple services.

File & Resource Names

Generate unique filenames for uploaded files to prevent conflicts and make files unpredictable. Cloud storage services and CDNs often use UUIDs to organize and reference stored objects.

API Keys & Tokens

Create unique API keys, OAuth tokens, and one-time passwords. UUIDs provide sufficient randomness for security tokens while maintaining a standard format that's easy to validate.

Frequently Asked Questions

Are UUIDs truly unique?

While not mathematically guaranteed, UUID v4 collisions are so unlikely they're considered impossible in practice. With 2^122 possible values, you'd need to generate billions of UUIDs per second for millennia to have a 50% chance of a single collision. Most applications will never see a duplicate.

What's the difference between UUID versions?

UUID v1 uses timestamps and MAC addresses (time-based), v3/v5 use MD5/SHA-1 hashing of names (namespace-based), and v4 uses random numbers. V4 is most common because it's simple and doesn't leak information about when or where it was generated, unlike v1.

Can I use UUIDs as passwords or secrets?

No! While UUIDs are unpredictable, they're not designed for cryptographic security. Use proper password hashing (bcrypt, Argon2) for passwords and cryptographically secure random generators for secrets and tokens. UUIDs are for identification, not authentication or encryption.

Are UUIDs case-sensitive?

The RFC 4122 standard recommends lowercase hexadecimal digits, but UUIDs are case-insensitive. "550e8400-e29b-41d4-a716-446655440000" and "550E8400-E29B-41D4-A716-446655440000" represent the same UUID. However, always use lowercase for consistency.

Can I generate UUIDs offline?

Yes! UUID v4 generation requires no network, central authority, or coordination. This tool works entirely in your browser using the Web Crypto API. You can generate millions of UUIDs offline with confidence they won't conflict with UUIDs generated anywhere else.

Should I include hyphens in UUIDs?

The standard format includes hyphens (8-4-4-4-12), which improves readability and is recognized by UUID-aware systems and libraries. Some systems strip hyphens for storage efficiency, but include them for display and APIs to maintain compatibility and human readability.

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