UUID generator and decoder
Generate random v4 or time-ordered v7 UUIDs, one at a time or ten thousand at once, or decode a UUID you already have to see its version and embedded time.
Generate UUIDs
Decode a UUID
Paste any UUID to check it and see its version, variant and, for v1, v6 and v7, the time inside it.
Try an example:
UUID v4 or v7?
| v4 | v7 | |
|---|---|---|
| Contents | 122 random bits | 48-bit Unix time in milliseconds, then 74 bits of counter and randomness |
| Reveals when it was made | No | Yes, to the millisecond, to anyone who decodes it |
| Sort order | Random | Roughly by creation time |
| Good for | Identifiers that must not leak timing | Database keys, where new rows land at the end of the index |
Both are defined by RFC 9562, which replaced RFC 4122 in 2024. If the identifier is a database key, v7 is usually the better default; if it is exposed and its age is nobody's business, use v4.
How ordered is v7?
Within one batch from this tool, every value is greater than the one before it. The generator keeps the sub-millisecond part of the clock in the 12 bits after the version, and never hands out a value lower than its last one, even if the server's clock steps back; in that case the embedded time runs slightly ahead of the real time until the clock catches up. That guarantee holds within one generator process only. Separate requests can be served by different processes, and UUIDs made on different machines are only as ordered as their clocks, so treat v7 as sorting roughly by creation time rather than as a strict sequence.
What decoding can and cannot tell you
The decoder reads the bits: the variant, the version and, for the time-based versions 1, 6 and 7, the embedded timestamp, shown in UTC. A v4 UUID has no time in it, and a name-based v3 or v5 UUID is a hash, so no creation time is shown for them. The nil UUID (all zeros) and the max UUID (all ones) are special values with no version. A UUID that parses is only well formed: it does not prove who made it, when it was really made or that it is unique, and a v7 timestamp is whatever the generator's clock said. UUIDs are identifiers, not secrets; do not use one as a password, session token or API key.
How these UUIDs are made
Values are generated by our Go API with the google/uuid library, from the operating system's cryptographic random source. They are returned to you and forgotten: not logged, stored or added to analytics, and the same is true of a UUID you decode.
More free tools
- Favicon & app icon generator - One image in, an icon package out: favicon, touch and PWA icons, manifest.
- Full page screenshot - Capture any website as a full page image in PNG, JPEG or WebP, at desktop, tablet or mobile size.
- HTML to image - Render HTML to a PNG, JPG or WebP image at the size you choose, fitted to the content or fixed.
- HTML to PDF converter - Turn pasted HTML or a public page into a PDF, with paper size, margins and backgrounds.
- Image converter - Convert WebP, PNG or JPEG images to PNG or JPG, with optional resizing. Metadata is stripped.
- XML invoice viewer - Open a UBL or Peppol invoice or credit note as a readable document, then download it as a PDF.
- Peppol invoice validator - Check a UBL invoice or credit note against EN 16931 and Peppol BIS Billing 3 rules, no account needed.
- UBL to PDF converter - Turn a UBL or Peppol invoice XML into a readable, paginated PDF, keeping the original XML.
- XRechnung validator - Check an XRechnung invoice or credit note in UBL or CII against the official XRechnung 3.0.2 rules.
- XRechnung viewer - Open an XRechnung in UBL or CII and read it as a document, with every value traced to its XML line.
- ZUGFeRD / Factur-X validator - Check a ZUGFeRD or Factur-X PDF or XML: the PDF/A, the embedded invoice and its metadata, and the ZUGFeRD 2.5.2 profile rules.
- QR code generator - Generate a QR code as PNG. Every code is decoded to verify it before delivery.
- QR code decoder - Decode a QR image or photo and see exactly what it contains, without opening the link.