UUID Generator

What Is a UUID and When Do You Need One?

A UUID (Universally Unique Identifier) is a 128-bit label used to identify information in computer systems without requiring coordination between the parties generating them. Standardised in RFC 4122, UUIDs are ubiquitous in modern software development — from database primary keys and API idempotency tokens to distributed tracing IDs and session identifiers.

UUID v4 is the most commonly used version. It generates 122 bits of cryptographically secure randomness, giving roughly 5.3 × 10³⁶ possible values. The probability of a collision is astronomically low, making v4 UUIDs safe for virtually any use case. UUID v1 embeds a 60-bit timestamp and a node identifier, which makes the IDs sortable by creation time but also means they can leak timing information. UUID v5 takes a namespace UUID and an arbitrary name, hashes them with SHA-1, and produces a deterministic result — the same inputs always yield the same UUID, which is useful for generating reproducible identifiers from known data.

ULIDs (Universally Unique Lexicographically Sortable Identifiers) are a newer alternative. They encode a millisecond-precision timestamp in the first 48 bits, followed by 80 bits of randomness, all represented in Crockford Base32. Because the timestamp comes first, ULIDs sort naturally by creation time — a significant advantage for database indexing and time-series data.

This tool generates all four types entirely in your browser using the Web Crypto API. No data leaves your machine. You can generate up to 1,000 IDs at once in various formats, and the built-in validator lets you quickly check and analyse any UUID you encounter in the wild.