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Development API Security

🕒 8 min • 🎯 Beginner to Advanced • 📅 July 2025

#### UUIDs are essential for ensuring data uniqueness and robust applications. Learn how to generate and use them effectively. ## Table of Contents 1. [What is a UUID?](#what-is-a-uuid) 2. [Why use UUIDs?](#why-use-uuids) 3. [How does a UUID v4 generator work?](#how-does-a-uuid-v4-generator-work) 4. [Best practices and mistakes to avoid](#best-practices-and-mistakes-to-avoid) 5. [Practical use cases](#practical-use-cases) 6. [FAQ](#faq) ###

What is a UUID?

A UUID (Universally Unique Identifier) is a 36-character string used to uniquely identify objects in a computer system. **Example**: `123e4567-e89b-12d3-a456-426614174000` ###

Why use UUIDs?

- **Guaranteed uniqueness**: Practically no collision possible - **Interoperability**: Standard recognized in all languages - **Security**: Hard to guess, ideal for tokens or private links UUID v4 Example

Generated UUID: 550e8400-e29b-41d4-a716-446655440000

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How does a UUID v4 generator work?

- Fully random generation (based on pseudo-random numbers) - Standard format: 8-4-4-4-12 hexadecimal characters - RFC 4122 compliant **Tip**: Always use version 4 for client-side or API generation, as it does not depend on timestamp or MAC address. ###

Best practices and mistakes to avoid

Do's

Use a reliable generator (well-known library or secure online tool)
Store UUIDs as text (VARCHAR, string)
Check uniqueness in your database
Use for primary keys, tokens, unique links

Don'ts

Reuse an already generated UUID
Use a UUID for sensitive data without encryption
Store a UUID as a number
Confuse UUID v1 (timestamp-based) and v4 (random)

###

Practical use cases

Web Development

Generate IDs for users, orders, files
Create access or reset tokens
Ensure resource uniqueness in a REST API

Databases

Universal primary keys (multi-server, sync)
Data migration between systems
Cross-referencing between tables

###

FAQ

- **Is a UUID really unique?** Yes, the probability of collision is extremely low (almost zero). - **Can a UUID be guessed?** No, they are generated randomly. - **Can I use a UUID as a password?** No, it's not meant for authentication security. - **Is a UUID case-sensitive?** No, it's generally case-insensitive. - **Should I store UUIDs in lowercase or uppercase?** Both are accepted, but consistency is recommended.

Complete Guide: Generate Unique UUIDs