Question 1

What is a UUID?

Accepted Answer

UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 4122. UUIDs are designed to be globally unique without requiring a central authority, making them ideal for distributed systems, databases, and APIs. A UUID looks like: 550e8400-e29b-41d4-a716-446655440000. Learn the difference between UUIDs and GUIDs in our detailed comparison.

Question 2

What are the different UUID versions?

Accepted Answer

This tool supports three UUID versions: (1) UUID v1 - Generated from timestamp and MAC address, ensuring uniqueness based on time and node identity. (2) UUID v4 - Completely random, using cryptographically secure random numbers. (3) UUID v5 - Generated from namespace and name using SHA-1 hashing, producing deterministic UUIDs for the same inputs. Read our detailed UUID versions comparison.

Question 3

When should I use UUID v1 vs v4 vs v5?

Accepted Answer

Use UUID v1 when you need sortable IDs that encode creation time, or need to prevent duplicates across nodes. Use UUID v4 (most common) when you need maximum randomness and don't care about ordering. Use UUID v5 when you need deterministic UUIDs - the same name and namespace always produce the same UUID, useful for consistent resource identifiers.

Question 4

Are UUIDs truly unique?

Accepted Answer

While the probability of collision is extremely low (practically zero for v4), UUIDs are not mathematically guaranteed to be unique. With 2^122 possible v4 UUIDs, you would need to generate about 2.71 quintillion UUIDs to have a 50% chance of collision. For practical purposes in software development, UUIDs are considered unique. Explore our UUID collision probability analysis.

Question 5

Can I use UUIDs as database primary keys?

Accepted Answer

Yes, but consider the tradeoffs. Benefits: globally unique without coordination, work in distributed systems, no sequential ID enumeration attacks. Drawbacks: larger storage (16 bytes vs 4-8 for integers), potentially slower indexing, not human-readable, random v4 UUIDs reduce database locality. For high-performance systems, consider UUID v1 or alternatives like ULID for better database performance. Read our detailed guide on UUID primary key pros and cons.

Question 6

Is UUID generation secure?

Accepted Answer

UUID v4 generation uses cryptographically secure random number generators (crypto.getRandomValues() in browsers, crypto module in Node.js), making them suitable for security-sensitive applications. However, UUID v1 may expose MAC address information. Never use UUIDs as secrets or authentication tokens - use proper cryptographic tokens instead. Learn about UUID security and privacy implications.

Question 7

What is a namespace in UUID v5?

Accepted Answer

Namespaces in UUID v5 are pre-defined UUIDs that categorize your generated UUIDs. Standard namespaces include: DNS (6ba7b810-9dad-11d1-80b4-00c04fd430c8) for domain names, URL (6ba7b811-9dad-11d1-80b4-00c04fd430c8) for URLs, OID for ISO OID, and X500 for X.500 DNs. You can also use custom namespace UUIDs for application-specific purposes. Learn when to use UUID v5 for deterministic ID generation.

Question 8

How do I generate multiple UUIDs at once?

Accepted Answer

Use the "Quantity" field to specify how many UUIDs to generate in a batch (1-100). This is useful for database seeding, testing, or creating multiple unique identifiers at once. Each generated UUID is guaranteed to be unique within the batch for v4 (random) and will follow sequential timestamps for v1. See how to generate UUIDs in different programming languages.

GUID/UUID Generator

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