UUID Generator — Complete Guide
A UUID (Universally Unique Identifier) is a 128-bit identifier formatted as a string like 550e8400-e29b-41d4-a716-446655440000. They are designed to be unique across systems without requiring a central authority to assign them — which makes them extremely useful in distributed software.
Version 4 UUIDs, the most common type, are generated using random numbers. The probability of generating two identical UUIDs is so astronomically small that for practical purposes, every UUID you generate is unique. This tool generates v4 UUIDs in your browser — nothing is sent to a server.
UUIDs are used everywhere in software: as primary keys in databases, as session identifiers, as tracking IDs for events and transactions, and as file names for uploads where name collisions would cause problems.
What you can do with UUID Generator
- Generating primary keys for database records without a central auto-increment counter
- Creating unique session tokens for user authentication
- Assigning unique IDs to uploaded files to prevent naming conflicts
- Generating tracking identifiers for events, logs, and transactions
- Creating test fixture IDs during development and QA
How to use UUID Generator
Click the Generate button to create a new UUID
Copy the UUID from the output field
Paste it into your code, database, or configuration
Generate as many as you need — each one is unique
Tips for best results
UUIDs are case-insensitive but conventionally written in lowercase
Store UUIDs as a CHAR(36) or use a native UUID type if your database supports it
For high-performance databases, consider whether UUID primary keys suit your indexing strategy — sequential IDs can sometimes perform better for B-tree indexes
UUID v4 is random. UUID v1 includes a timestamp and MAC address — use v4 for anything where privacy matters
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Frequently asked questions
Are UUIDs truly unique?
In practice, yes. The probability of generating a duplicate UUID v4 is about 1 in 5.3 undecillion. You would need to generate billions of UUIDs per second for thousands of years to have a realistic collision risk.
What is the difference between UUID v1 and v4?
UUID v1 is based on the current timestamp and the MAC address of the generating machine, which makes it traceable. UUID v4 is randomly generated and contains no identifying information, making it more privacy-friendly.
Can I use UUIDs as database primary keys?
Yes, and many applications do. The tradeoff is that random UUIDs cause more page splits in B-tree indexes compared to sequential integers, which can affect insert performance at very high scale.
Is this tool safe to use for production IDs?
This tool uses your browser's built-in cryptographic random number generator, which produces UUIDs suitable for production use. Nothing is sent to any server.