Learn what a UUID is, the difference between UUID versions, how to generate one, and when to use UUIDs as unique identifiers in your applications.
Step-by-Step Guide
Understand what a UUID is
A UUID (Universally Unique Identifier) is a 128-bit identifier formatted as 8-4-4-4-12 hexadecimal digits: e.g., 550e8400-e29b-41d4-a716-446655440000. The probability of collision is astronomically low.
Know the UUID versions
UUID v1: based on timestamp + MAC address. UUID v4: randomly generated (most common for app dev). UUID v5: namespace + name hashed with SHA-1. UUID v7 (newer): time-ordered random, better for database indexing.
Generate a UUID with our tool
Open the UUID Generator, select the version (v4 for general use), and click Generate. You can generate single or bulk UUIDs and copy them to clipboard.
Use UUIDs in your code
JavaScript: crypto.randomUUID() (built-in). Python: import uuid; uuid.uuid4(). Go: github.com/google/uuid. Most databases (PostgreSQL, MySQL) have native UUID types and functions.
When to use UUID vs auto-increment ID
Use UUID when: merging records from multiple databases, exposing IDs in URLs (avoids enumeration attacks), or working in distributed systems. Use auto-increment when: you need sortable IDs, smaller storage, or human-readable row numbers.
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Frequently Asked Questions
Q: Can two UUIDs ever be the same?
A: Theoretically yes, but the probability is so low (1 in 5.3×10³⁶ for v4) it's treated as impossible in practice. The UUID spec was designed specifically to avoid this.
Q: Is UUID v4 secure enough for session tokens?
A: UUID v4 is randomly generated but not cryptographically secure in all environments. For session tokens, use cryptographically secure random generation (e.g., crypto.randomBytes in Node.js).
Q: What is a GUID? Is it the same as UUID?
A: GUID (Globally Unique Identifier) is Microsoft's term for UUID. They use the same format and algorithm. GUID and UUID are interchangeable in practice.