UUID Generator — Tutorial

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit identifier used to uniquely identify information in distributed systems without requiring a central authority. UUIDs are standardized by RFC 4122 and are virtually guaranteed to be unique across space and time.

UUID Format

UUIDs are typically displayed as 32 hexadecimal digits in groups: xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx

Where M indicates the version (1-5) and N indicates the variant.

UUID Versions

Version 1 (Time-based)

• Based on current timestamp and MAC address
• Guarantees uniqueness across time and space
• Can reveal information about when and where it was created
• Example: 6ba7b810-9dad-11d1-80b4-00c04fd430c8

Version 4 (Random)

• Generated using random or pseudo-random numbers
• Most commonly used version
• No information leakage about time or location
• Example: f47ac10b-58cc-4372-a567-0e02b2c3d479

When to use each version

• Version 4: Default choice for most applications. Use when you need unique IDs without revealing metadata.
• Version 1: Use when you need to sort UUIDs by creation time or need guaranteed uniqueness even with poor random number generators.

Official documentation

• RFC 4122 - UUID Specification
• MDN: crypto.randomUUID()
• UUID Generator - Online tool and examples

How to use the UUID Generator

1. Choose version — Select V1 (time-based) or V4 (random) from the dropdown.
2. Set quantity — Enter the number of UUIDs to generate (1-1000).
3. Generate — Click Generate to create the UUIDs.
4. Copy or download — Use Copy all or the download link for the results.
5. History — Last 5 generations are stored locally. Use Clear history to remove them.

Open the tool: UUID Generator

Privacy & limits

• All UUID generation is performed locally in your browser; no data is uploaded.
• V1 UUIDs use a randomly generated MAC address (not your real one) stored in localStorage.
• Maximum batch size: 1000 UUIDs per generation.
• History stores last 5 batches in your browser's localStorage.

Troubleshooting

• Large batches: Generating 1000 UUIDs may take a few seconds. The browser may appear frozen briefly.
• V1 timestamp issues: Our V1 implementation is best-effort for browsers. Server-side libraries may generate different V1 UUIDs for the same timestamp.
• Uniqueness concerns: While extremely unlikely, V4 UUIDs have a tiny probability of collision. V1 UUIDs are guaranteed unique if generated on the same machine.
• Storage limitations: History is stored in localStorage and may be cleared by the browser.

Best practices

• Use V4 by default: Unless you specifically need the properties of V1
• Store as binary: In databases, store UUIDs as 128-bit binary, not as 36-character strings
• Avoid sequential ordering: V4 UUIDs are not sortable by creation time
• Consider alternatives: For high-performance databases, consider ULIDs or other time-sortable alternatives