UUID Generator

What Is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit identifier represented as 32 hexadecimal digits in the format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. Despite being only 36 characters, it encodes a number so astronomically large that generating two identical UUIDs by random chance is practically impossible — the probability is comparable to winning a lottery millions of times in a row.

Version 4 (Random) UUIDs

This tool generates UUID version 4, which uses 122 bits of cryptographic randomness. The remaining 6 bits encode the version (4) and variant (RFC 4122) markers. V4 is the most widely used UUID type because it requires no network address, no central counter, and no coordination between systems. The total space of v4 UUIDs is 2¹²² — approximately 5.3 × 10³⁶ possible values.

Format Options

Standard format uses lowercase hex with hyphens: 550e8400-e29b-41d4-a716-446655440000. UPPERCASE is the same value capitalised — some legacy systems require this. No hyphens removes the separators, producing a 32-character string: 550e8400e29b41d4a716446655440000 — useful for compact storage or systems that cannot handle hyphens in identifiers.

When to Use UUIDs

• Database primary keys: Unlike auto-increment integers, UUIDs can be generated client-side without a database round-trip, enabling offline-first patterns.
• Distributed systems: Multiple services or devices can independently generate IDs with no coordination and no collisions.
• File naming: Uploaded files stored with UUID names prevent collisions and avoid exposing original filenames.
• API request tracing: Assign each request a UUID for end-to-end log correlation across microservices.
• Security: UUIDs do not reveal count or sequence, unlike auto-increment IDs (ID 1042 implies ~1,041 other records exist).