UUID v4 Generator
Generate random UUID v4 identifiers instantly — free, client-side, no data sent to servers.
Generate UUIDs
Validate UUID Format
Enter one or more UUIDs (one per line) to check if they are valid UUID v4.
Frequently Asked Questions
What is a UUID v4? ▼
UUID v4 (Universally Unique Identifier version 4) is a randomly generated 128-bit identifier, formatted as xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where x is a random hex digit and y is one of 8, 9, a, b. It is standardized by RFC 4122.
Are these UUIDs truly random? ▼
Yes. This tool uses the Web Crypto API (crypto.getRandomValues) built into all modern browsers, which provides cryptographically strong random numbers — exactly what UUID v4 requires per the RFC.
Is my data sent to a server? ▼
No. All UUID generation and validation runs entirely in your browser using JavaScript. Nothing is ever transmitted to any server. Your UUIDs stay private.
How many UUIDs can I generate at once? ▼
You can generate between 1 and 10,000 UUIDs in a single batch. For very large batches (thousands), the browser may take a brief moment to render the output.
What is UUID v4 used for? ▼
UUID v4 is widely used as unique identifiers for database primary keys, distributed system records, session tokens, API request IDs, file names, and anywhere a globally unique ID is needed without central coordination.
What's the difference between UUID versions? ▼
UUID v1 uses timestamp + MAC address; v3 uses MD5 hashing of a namespace+name; v4 is fully random (most common); v5 uses SHA-1 hashing; v7 uses a Unix timestamp prefix for sortability. v4 is the go-to choice when you just need a unique, random ID.
About UUID v4
A UUID (Universally Unique Identifier) is a 128-bit label defined by RFC 4122. In version 4, all bits are random except for two fixed fields indicating the version (4) and variant. The probability of generating two identical UUID v4s is astronomically small — roughly 1 in 5.3×10³⁶. This makes them safe to use as unique identifiers in databases, APIs, and distributed systems without any central authority.
Format: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx — 32 hex digits + 4 hyphens = 36 characters total.