UUID Generator

Runs in browser Utilities

Create one or thousands of RFC 9562 UUIDs (v4, v7, or nil), in lowercase, uppercase, braces or without dashes, and decode the version and variant of any UUID.

Privacy: This tool runs entirely in your browser. Your input never leaves your device.

How to use UUID Generator

  1. Choose the version, count and format, then click Generate.
  2. Copy the list or download it as a text file.
  3. To inspect an existing UUID, paste it in the validate box and click "Validate / decode".

UUID Generator features

  • UUID v4 (random) and v7 (time-ordered, RFC 9562), plus Nil and Max
  • Generate 1–1000 at once with cryptographically secure randomness
  • Formats: lowercase, UPPERCASE, {braces}, no dashes, urn:uuid:, Base64
  • Validate any UUID and decode version, variant and embedded timestamp
  • v7 IDs generated in the same millisecond stay strictly ordered
  • Regenerate for a fresh batch

UUID Generator example

Decode a v7 UUID

Input:

0190f7a4-3f9e-7c2b-9d3a-5e1b2c3d4e5f

Output:

Valid ✓ · Version: v7 — Unix epoch time-ordered · Variant: RFC 4122 / 9562 · Timestamp: 2024-07-28T04:40:54.942Z

Frequently asked questions about UUID Generator

What is the difference between UUID v4 and v7?

v4 is 122 bits of randomness — unpredictable but unordered. v7 (RFC 9562) starts with a 48-bit Unix millisecond timestamp, so IDs sort by creation time, which keeps database indexes compact.

Is the randomness secure?

Yes. IDs are generated with the browser's crypto.getRandomValues, the same source used for keys and tokens.

Can I decode an existing UUID?

Paste it into the validate box and click "Validate / decode" to see its version, variant, and for v1/v6/v7 the embedded timestamp (plus clock sequence and node for v1/v6).

Which formats are available?

Lowercase, UPPERCASE, {braces} (Microsoft style), no dashes, urn:uuid: and Base64.

How many can I generate at once?

Up to 1000 per click; use Regenerate for a fresh batch.

Technical notes

v4 takes 16 bytes from crypto.getRandomValues and overwrites the version and variant bits, leaving 122 random bits. v7 writes the 48-bit Unix millisecond timestamp big-endian into the first six bytes and, within one batch, replaces rand_a with a 12-bit counter restarting at 0 every millisecond (RFC 9562 §6.2, method 1): consecutive IDs in one millisecond differ by one in the third group (…-7000-, -7001-…) and only rand_b's 62 bits are random.

Decoding reads the version from hex digit 13 and the variant from digit 17 (0–7 NCS, 8–b RFC 4122/9562, c–d Microsoft, e–f reserved); version labels are flagged as meaningless outside the RFC variant. v1 and v6 timestamps are rebuilt with BigInt from 100-ns intervals since 1582-10-15 (offset 0x01B21DD213814000), and the node's multicast bit separates random nodes from MAC addresses. Base64 is the standard alphabet with '==' padding, not base64url; v3/v5 are not generated.