Tools
UUID generator
Generate cryptographically-random UUIDs right in your browser. Choose classic version 4 (fully random) or time-ordered version 7 (sortable, index-friendly), bulk generate up to 100 at a time, and copy them individually or all at once. Everything runs client-side, so no UUID ever leaves your machine.
Generated in your browser with the Web Crypto API. Nothing is sent to a server: no network requests, no logging.
Choose your options and press Generate to create UUIDs.
v4 vs v7: which should you pick?
UUID v4 is 122 bits of randomness with version and variant bits set. It is the safe default when you want an opaque identifier that reveals nothing about when it was created: API keys' public ids, correlation ids, idempotency keys, and anything exposed to clients.
UUID v7 prefixes the value with a 48-bit Unix millisecond timestamp, then fills the rest with random bits. Because the leading bytes increase over time, v7 values are lexicographically and chronologically sortable. That keeps database indexes compact (new rows land at the tail of a B-tree instead of being scattered), so v7 is the better primary key for high-insert tables in PostgreSQL, MySQL, or SQLite.
Frequently asked questions
- What is the difference between UUID v4 and v7?
- A v4 UUID is 122 bits of pure randomness, great for opaque, unguessable identifiers. A v7 UUID puts a 48-bit millisecond timestamp at the front, so IDs generated later sort after earlier ones. That makes v7 friendlier to database indexes and natural chronological ordering.
- When should I use v7 instead of v4?
- Use v7 for primary keys and anything you store in a B-tree index. Because v7 is time-ordered, new rows are inserted near the end of the index instead of scattered randomly, which reduces page splits and keeps inserts fast. It also lets you sort records by creation time without a separate timestamp column.
- Are these UUIDs cryptographically random?
- Yes. The random bits come from the Web Crypto API (crypto.randomUUID for v4 and crypto.getRandomValues for v7), which is a cryptographically secure pseudo-random number generator provided by your browser. They are suitable for identifiers, not for secret keys.
- Does this tool send my UUIDs anywhere?
- No. Generation happens entirely in your browser. There are no network requests, no analytics on the values, and nothing is stored on a server. You can even run it offline once the page has loaded.