Tool Fu
$ toolfu run uuid-generator

UUID Generator — Generate Random UUIDs Online

Free online UUID generator. Generate random v4 UUIDs instantly using the cryptographically secure Web Crypto API. Bulk UUID generation — runs entirely in your browser.

all processing runs in your browser
uuid-generator
count:
output > 1 uuid
a0e50191-b44f-4555-843a-209547dd6d76

v4 UUIDs generated using crypto.randomUUID() — cryptographically secure

Generate UUIDs — Fast and Private

UUIDs (Universally Unique Identifiers) are essential building blocks in software development. They serve as database primary keys, session identifiers, API request IDs, correlation tokens, and more. Unlike auto-incrementing integers, UUIDs can be generated independently on any device without coordination, making them ideal for distributed systems.

This tool generates UUID v4 — the most widely used version — using your browser's built-in crypto.randomUUID() API. Every UUID is cryptographically random and generated locally. Nothing is sent to a server.

Common UUID use cases

  • Database primary keys (PostgreSQL, MongoDB)
  • Distributed system identifiers
  • Session and request correlation IDs
  • File naming to avoid collisions
  • API idempotency keys

UUID v4 format

A v4 UUID follows the pattern xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where x is any hex digit and y is one of 8, 9, a, or b. The 4 in the third group identifies it as version 4. The total length is 36 characters including hyphens (32 hex characters).

$ cat FAQ.md
What is a UUID?▶
A UUID (Universally Unique Identifier) is a 128-bit identifier that is practically guaranteed to be unique across all devices and time. The most common format is UUID v4, which uses random or pseudo-random numbers. UUIDs are represented as 32 hexadecimal characters separated by hyphens in the pattern 8-4-4-4-12.
Are these UUIDs cryptographically secure?▶
Yes. This tool uses the Web Crypto API via crypto.randomUUID(), which generates cryptographically strong random values. The UUIDs are generated entirely in your browser — nothing is sent to a server.
What is the difference between UUID versions?▶
UUID v1 uses the current timestamp and MAC address. UUID v3 and v5 are generated from a namespace and name using MD5 or SHA-1 hashing. UUID v4 is fully random — this is the version generated by this tool and the most commonly used in modern applications.
Can two UUIDs ever be the same?▶
In theory, yes. In practice, no. The probability of generating two identical v4 UUIDs is about 1 in 2^122 (5.3 x 10^36). You would need to generate 2.71 quintillion UUIDs to have a 50% chance of a single collision.