UUID Generator

What is a UUID generator?

A UUID generator creates universally unique identifiers — the long strings like f47ac10b-58cc-4372-a567-0e02b2c3d479 you use as primary keys, request IDs, file names, and idempotency tokens. The whole point of a UUID is that you can mint one anywhere, on any machine, without coordinating with a central server, and still be confident it won't collide with anyone else's.

This generator does more than the single-purpose sites that only spit out v4. It supports three modern formats — UUID v4, UUID v7, and ULID — generates them in bulk, and does it all locally in your browser using the cryptographically secure Web Crypto API.

How to use it

1. Pick an identifier type: UUID v4 (random), UUID v7 (time-ordered), or ULID (sortable, base32).
2. Set the quantity (1–100).
3. Optionally toggle Uppercase or Remove dashes (UUIDs only).
4. Press Generate for a fresh batch.
5. Copy any single ID, Copy all, or Download .txt to grab the whole list.

A first batch is created automatically when the tool loads, so there's always something to copy.

UUID v4 — random

UUID version 4 is 122 bits of randomness with a few bits fixed to mark the version and variant. It's the default everyone reaches for, and for good reason: it's simple, unpredictable, and has no structure that leaks information about when or where it was created.

The tradeoff shows up at scale in databases. Because v4 values are random, consecutive inserts land in random spots of a B-tree index, causing page splits and poor cache locality. For a few thousand rows that's irrelevant; for high-insert tables it can hurt.

UUID v7 — time-ordered

UUID version 7 fixes the index problem while keeping global uniqueness. The first 48 bits are a Unix millisecond timestamp, followed by random bits (with the version and variant markers in place). Because the timestamp leads, IDs created later sort after earlier ones:

• Index-friendly. New rows append near the "end" of the index instead of scattering — far fewer page splits.
• Roughly sortable by creation time without a separate created_at column.
• Still globally unique thanks to the random tail.

If you're choosing a primary key for a new table today, v7 is usually the better default than v4.

ULID — sortable and compact

A ULID (Universally Unique Lexicographically Sortable Identifier) is a different encoding with the same time-ordered idea. It's 26 characters of Crockford base32: a 48-bit timestamp followed by 80 bits of randomness, e.g. 01ARZ3NDEKTSV4RRFFQ69G5FAV.

• Lexicographically sortable — sorting the strings sorts them by time.
• Compact and URL-safe — shorter than a UUID, no dashes, safe in URLs and file names.
• Case-insensitive — the Crockford alphabet omits the confusable characters I, L, O and U.

ULIDs shine when you want readable, sortable IDs in URLs, logs, or object keys.

Which should I use?

• Default for new database keys: UUID v7 — globally unique and index-friendly.
• You need maximum opacity / no time leakage: UUID v4 — pure randomness, no embedded timestamp.
• You want short, sortable, URL-safe IDs: ULID.
• Interoperating with an existing system: match whatever it already uses.

A quick note on privacy of the IDs themselves: v7 and ULID embed the creation time, which is fine for most internal keys but means an outsider can read roughly when the ID was made. If that's sensitive, prefer v4.

The privacy wedge: every ID is made on your device

This is the part that separates a serious dev tool from a throwaway page. Every identifier here is generated with crypto.getRandomValues (and the native crypto.randomUUID where available) — the browser's own cryptographically secure random number generator — running entirely on your machine.

That means:

• No server round-trip. Open your network tab while generating a thousand IDs and you'll see zero requests. The IDs can't be intercepted because they're never transmitted.
• No logging. A server-side generator could, in principle, keep a copy of every ID it hands you. Here there's nothing to keep.
• Works offline. Because it's pure client-side JavaScript, it keeps working with no connection at all.

Single-purpose "UUID v4 only" sites often render server-side or pull from an API — and they rarely support v7 or ULID, so you end up juggling multiple tools. This one covers all three modern formats, does bulk, and keeps every byte of randomness on your device.

Tips

• Don't use UUIDs as security tokens unless they're v4 — and even then prefer a dedicated Password Generator for anything that grants access.
• Pick one format per table and stick with it for clean, predictable indexes.
• Bulk + download is handy for seeding test data — generate 100, save the .txt, import. When you need whole records rather than bare IDs, the Fake Data Generator fills in matching names, emails and addresses.

Choose a type, generate, and copy — fast, local, and private.