UUID / GUID Generator
Generate cryptographically secure Version 4 UUIDs (GUIDs) in bulk. Custom formatting, uppercase/lowercase, hyphens, and instant bulk copy.
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What is a Universally Unique Identifier (UUID)?
A Universally Unique Identifier (UUID), also known as a Globally Unique Identifier (GUID), is a 128-bit number used to identify information in computer systems. Standardized by RFC 4122 and ITU-T X.667, UUIDs are designed to enable distributed systems to uniquely identify information without central coordination or authority.
Structure of a UUID Version 4
In its canonical textual representation, a UUID is expressed as 32 hexadecimal digits displayed in five groups separated by hyphens, in the form 8-4-4-4-12 for a total of 36 characters (e.g., f47ac10b-58cc-4372-a567-0e02b2c3d479).
For a Version 4 UUID, the 13th hexadecimal character (the first character of the 3rd group) is set to 4 to designate version 4. Additionally, the 17th hexadecimal character (the first character of the 4th group) is set to one of 8, 9, a, or b to indicate the variant specified in RFC 4122.
Cryptographic Randomness & Security
Standard Math.random() pseudo-random number generators in older programming environments are predictable and unsuitable for security-sensitive UUID generation. FreeFileTool uses the modern W3C Web Cryptography API (crypto.getRandomValues or crypto.randomUUID()), ensuring every generated bit comes directly from the operating system's CSPRNG pool.
Common Use Cases for UUIDs
- Database Primary Keys: Preventing key collision across distributed SQL databases and microservice clusters.
- API Tracking IDs: Assigning correlation IDs to HTTP requests and asynchronous job queues.
- Session Identifiers: Creating unguessable authentication token seeds.
- Unique File Names: Eliminating file overwrite collisions on object stores.
Frequently Asked Questions
How are UUID v4 identifiers generated in this tool?
FreeFileTool generates UUIDs using your browser's native window.crypto.getRandomValues() API, which accesses system-level cryptographically secure random number generation (CSPRNG).
What is the probability of a UUID v4 collision?
UUID v4 uses 122 bits of random data. To have a 50% chance of a single collision, you would need to generate approximately 2.71 quintillion UUIDs (2.71 x 10^18), making collisions virtually impossible in practical applications.
What is the difference between UUID v1, v4, and v5?
UUID v1 is time-and-MAC-address based; UUID v4 is purely randomly generated; UUID v5 is namespace-and-name based using SHA-1 hashing. Version 4 is the most popular choice for web applications due to privacy and simplicity.
Can I use these generated UUIDs in databases and production applications?
Yes, all generated UUIDs strictly comply with RFC 4122 standards and are fully suitable for primary keys, database identifiers, session IDs, and API request tracking.