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v4 random · v7 time-based

Bulk-generate UUIDs and pick the formatting that matches your target system.

Format
  • 00159d0496a-0b2d-4228-a2b5-e5c7cb5a3afd
  • 0025af7bb97-4e73-4010-86f3-0147e84d9791
  • 0039db4fd43-d770-4d2f-9a60-c920eea60294
  • 0048aaea6f0-660f-4aad-b9bc-215553fd2c21
  • 0055bba7932-5d9a-400d-9c4d-97cc6dc8511e
  • 006ae46b24b-671c-4d5e-9c36-d924c1d33ee0
  • 00726ead576-bea6-4316-bed5-97feb33d7d94
  • 008b2db436e-c683-419e-b5ea-374859f3f464
  • 009507512db-adbf-49b9-aa8a-4bc952e3049c
  • 010877204e9-c4ed-4bff-8d1d-1b2777f85d0e
Everything happens in your browser. Nothing is uploaded.

When to use it

Seeding test rows, cache keys, throwaway session tokens. Under the hood this hits crypto.randomUUID(), so on any modern platform the output is cryptographically random.

v4 vs v7

  • v4 — fully random. All 128 bits minus 6 version/variant bits are random. The common default.
  • v7 — the first 48 bits are a Unix-millisecond timestamp, which makes them sortable in time order. Useful for database primary keys because inserts stay close together and indexes stay less fragmented. (RFC 9562, standardized in 2024.)

Formatting

  • With hyphens — the canonical xxxxxxxx-xxxx-… form.
  • No hyphens — Mongo ObjectID replacements, URL slugs.
  • {braces} — what legacy Windows GUID surfaces expect.
  • Uppercase — COM GUIDs, old .NET conventions.

The toggles compose, so you can combine "no hyphens + uppercase" for a 32-char compact form.

Where are the identifiers generated?

UUIDs are generated on the fly via the browser's crypto API. Nothing is sent or saved. Close the tab and they're gone.

Frequently asked questions

Are these UUIDs cryptographically secure?
Yes. The tool uses the browser's `crypto.randomUUID()` (v4) and `crypto.getRandomValues()` (v7's random portion) — Web Crypto's CSPRNG. Suitable for API keys, session tokens, and other security-sensitive uses.
What's the difference between v4 and v7?
v4 is fully random (122 bits of randomness). v7 (RFC 9562, 2024) puts a 48-bit Unix-millisecond timestamp at the front, with the rest random — making them sortable in time order. Great for database primary keys; reduces index fragmentation on insert.
Can I generate many at once?
Yes. Set the count to anywhere between 1 and 1000 in the top control. After generating, use "Copy all" or download as a txt file.
Are UUIDs really unique?
Probabilistically. v4 has 122 bits of randomness, so collisions are vanishingly unlikely (you'd need to generate billions before any reasonable chance). The same machine generating UUIDs back-to-back will not collide.
Why use UUIDs instead of auto-increment IDs?
Three reasons: (1) distributed systems — multiple servers can mint IDs without coordination, (2) URL safety — IDs don't enumerate (`/users/3`) so attackers can't guess other users' resources, (3) merge friendly — you can combine data from different databases without ID renumbering.
How long is a UUID?
36 characters in the canonical hyphenated form (`xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx`), 32 characters without hyphens, 16 bytes (128 bits) in binary.