UUID Generator

What this tool does

A UUID — Universally Unique Identifier — is a 128-bit value written as 32 hexadecimal digits, usually grouped as 8-4-4-4-12. This generator produces valid RFC 4122 UUIDs in two flavours: version 4, which is almost entirely random, and version 1, which is time-based. You can generate up to 100 at once and format them to suit wherever they are going. Every value is created on your own device using the browser’s Web Crypto API.

Why you might need it

UUIDs are the default way to give something a unique name without a central authority handing out IDs. Developers use them for database primary keys, so records can be created offline or across multiple services without colliding. They appear as request and trace identifiers in logs, as idempotency keys for API calls, as filenames for uploads, and as session or device tokens. Whenever you need an identifier that two independent systems can both generate without coordinating, a UUID is the standard answer.

How to use it

1. Choose a version — v4 (random) is the right pick for almost everything.
2. Set how many you want: 1, 5, 10, 25, or 100.
3. Toggle Hyphens off if your target format wants the bare 32 characters, and Uppercase on if your code style or database expects it.
4. Click Generate.
5. Copy any single UUID with the button beside it, or use Copy all to grab the whole batch at once.

Common pitfalls

The biggest mistake is reaching for v1 by default. Because v1 encodes a timestamp, two v1 UUIDs created close together are similar — which can leak roughly when a record was made and makes them less suitable as hard-to-guess tokens. Unless you specifically need time-ordering, use v4. A second pitfall is storing UUIDs inefficiently: keeping them as 36-character text in a database is convenient but larger and slower to index than storing the 16 raw bytes. Finally, remember a UUID is an identifier, not a secret — v4 UUIDs are unpredictable, but if you need a true security token, generate one explicitly for that purpose.

Tips and advanced use

For high-volume database inserts, plain v4 UUIDs can fragment an index because each new key lands in a random spot; if that matters, look at time-ordered schemes such as UUIDv7 or ULIDs, which keep the uniqueness while staying roughly sortable. When you need many IDs for test fixtures or seed data, generate 100 at once and copy them in a single block. And because this tool runs entirely client-side, it is safe to use even on an air-gapped machine — no network connection is required once the page has loaded.