UUID Generator

How to Use

1. Set how many UUIDs you want to generate (1 to 50).
2. Toggle uppercase if you prefer capital letters.
3. Click Generate to create the UUIDs.
4. Click Copy on any UUID, or Copy All for the full list.

About This Tool

A UUID (Universally Unique Identifier) is a 128-bit identifier that is practically guaranteed to be unique. Version 4 UUIDs are generated using random or pseudo-random numbers. They are widely used as database primary keys, session tokens, correlation IDs, and anywhere a unique identifier is needed without coordination between systems. This tool uses the browser's built-in crypto.randomUUID() when available for cryptographically strong randomness.

What Is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit number used to identify information in computer systems. Written as 32 hexadecimal digits separated by hyphens in five groups (like 550e8400-e29b-41d4-a716-446655440000), UUIDs are designed to be unique across space and time without requiring a central authority to issue them.

Version 4 UUIDs, which this tool generates, are created using random or pseudo-random numbers. Out of the 128 bits, 6 are reserved to indicate the version and variant, leaving 122 random bits. This gives roughly 5.3 x 10^36 possible values — so the probability of generating a duplicate is astronomically small, even if you generate billions of them.

UUIDs are defined by RFC 4122 and are a foundational building block in distributed systems. Unlike auto-incrementing database IDs, UUIDs can be generated independently by multiple systems without any risk of collision, making them ideal for microservices, event sourcing, and offline-capable applications.

Frequently Asked Questions

Are UUIDs truly unique?

In practice, yes. With 122 random bits, the chance of generating two identical v4 UUIDs is about 1 in 2^122 (roughly 5.3 x 10^36). You would need to generate about a billion UUIDs per second for 85 years to have a 50% chance of a single collision. For all practical purposes, they are unique.

What is the difference between UUID versions?

Version 1 UUIDs use the current timestamp and the device's MAC address. Version 4 (generated here) uses random numbers. Version 5 uses a namespace and name hashed with SHA-1. Version 7 (newer) combines a Unix timestamp with random data for sortable IDs. Each version serves different needs.

Can I use UUIDs as database primary keys?

Yes, and many applications do. UUIDs work well as primary keys because they can be generated client-side without database coordination. However, random v4 UUIDs can cause index fragmentation in B-tree indexes. If this is a concern, consider UUIDv7, which is time-sorted and more index-friendly.

Should UUIDs be uppercase or lowercase?

RFC 4122 states that UUIDs should be treated as case-insensitive. However, lowercase is the most common convention and what most libraries produce by default. This tool gives you a toggle to choose whichever format your project requires.

Common Use Cases

• Database primary keys — Use UUIDs instead of auto-incrementing integers for globally unique row identifiers.
• Distributed systems — Generate IDs independently across multiple services without a central ID server.
• Session tokens — Create unique session identifiers for user authentication and tracking.
• File naming — Assign unique names to uploaded files to prevent overwrites and collisions.
• Correlation IDs — Trace requests across microservices by attaching a UUID to each transaction.