Check a UUID you already have
UUID v4 + v7 · Local tool
UUID Generator
Generate v4 or time ordered v7 UUIDs, and read the version out of one you have.
Last updated
How do I generate a UUID without a server?
filetity's UUID generator makes them in the browser tab using crypto.getRandomValues, the cryptographic random source built into every modern browser, so no server ever sees the values. Pick version 4 for a purely random identifier, which is what most people mean by a UUID, or version 7 for one whose leading 48 bits are a millisecond timestamp, so the values sort in creation order and behave well as a database primary key. Up to 1000 can be generated at once, with or without hyphens, in upper or lower case, and in braces for Microsoft tooling that expects that form. There is also a checker that reads the version, the variant and, for a version 7, the moment it was created back out of a UUID you already have.
01 / Your device
the file stays here
02 / Browser memory
the work runs locally
03 / Back to you
saved on this device
When you would use this
Situations, not settings.
- Seeding test data or a migration
- Generate a hundred at once and paste them straight into a fixture or a SQL insert. Version 7 keeps them in creation order, which makes the rows readable afterwards.
- A database key that will not fragment the index
- Random v4 keys scatter inserts across a B-tree. Version 7 puts a timestamp in the leading bits so new rows append instead, which is why Postgres and MySQL docs now recommend it.
- Working out where a UUID you found came from
- Paste it into the checker and it reads back the version and the variant, and for a version 7 the exact millisecond it was created.
How it works / no cloud
A conversion engine, not an upload form.
The bytes come from crypto.getRandomValues, the browser's cryptographic random source, and never from Math.random, which is not seeded to be unpredictable in any engine. The version and variant bits are stamped in as RFC 9562 requires. Nothing is requested from a server, so no machine other than yours has ever held these values.
- Offline ready
- Installable app
- No file limit queue
Straight answers
No accordion. Nothing hidden.
- Is it free?
- Yes, with no watermark and no page limit.
- Does it need an account?
- No. There is no account system.
- Is my file processed on my device?
- Yes. The file is read by your browser and never uploaded. There is no server to send it to.
- What formats are supported?
- UUID version 4 and version 7. Output with or without hyphens, in lower or upper case, and optionally in braces.
- What are the limits?
- Up to 1000 at a time. More than that is a script's job rather than a web page's, and the page says so instead of freezing.
- Does it work on mobile?
- Yes, on any modern mobile browser. Large files are limited by the memory the phone gives the browser.
- Does it work offline?
- Yes, once the page has loaded. The tool keeps working with no network connection.
- What is a version 7 UUID and when should I use one?
- It puts a millisecond timestamp in the first 48 bits, so v7 values sort in the order they were created, as text and as bytes. That matters when the UUID is a database primary key: random keys scatter inserts across the whole index and fragment it, while time ordered keys append to the end. It became an RFC in May 2024.
- Are these safe to use as secret tokens?
- For a session token or a password reset link, use a purpose built token rather than a UUID. A v4 carries 122 random bits, which is plenty of entropy, but a v7 spends 48 of its bits on a timestamp anyone can read back, and UUIDs turn up in logs and URLs where secrets should not be.
- Is a GUID the same thing as a UUID?
- Yes. GUID is Microsoft's name for it and UUID is the name in the RFC, and the two describe the same 128 bit value. The one difference you will meet is presentation: Microsoft tooling often writes them wrapped in braces and in capitals, which is why both are options here.
- Could this generate a UUID somebody else already has?
- In practice no. A version 4 has 122 random bits, and you would need to generate around 2.7 quintillion of them before a collision became likely at all. The realistic failure is not the mathematics but a weak random source, which is why this uses the browser's cryptographic one.
- Why do all my version 7 UUIDs start with the same characters?
- Because they were made in the same millisecond and share a timestamp, and that is the feature rather than a fault. Their leading characters will differ from ones you generate tomorrow, and the last 74 bits are still random, so they remain unique.
Keep working locally
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