UUID Generator
Fresh UUIDs on demand. v4, v7, or v1.
What this does
Pick a version, pick how many, hit Generate. You get UUIDs one per line, ready to copy or download. If a teammate sent you here: a UUID is a 128-bit identifier you can mint on any machine, without checking in with a central server, and still trust that nobody else will ever produce the same one.
Common use cases
Primary keys and record IDs. Generate one when you create a row, a document, or a message, and you never have to ask the database for the next number in a sequence.
Idempotency keys and request IDs. Tag an API call with a UUID so a retry doesn't charge the card twice, or trace a single request as it hops across a dozen services.
Test data. Need 500 unique IDs to seed a fixtures file? Set the count, download the list, move on.
Things to know
v4 is random and the right default. v7 is the newer one worth knowing about: it puts a millisecond timestamp at the front, so the IDs sort in roughly the order you created them. That sounds cosmetic until you use them as database keys, where random v4 values scatter writes across the whole index and v7 values land neatly at the end. v1 is the old time-based format. The classic spec builds it from your MAC address; this tool uses a random node instead, because a browser can't read your MAC and has no business trying.
GUID is the same thing under a different name. If a Windows or .NET tool asks for a GUID, generate a UUID and you're done. Those tools tend to like uppercase, sometimes wrapped in braces, which the Uppercase toggle covers.
Privacy
Every ID is generated in your browser with the Web Crypto API. Nothing gets requested from a server, because there's no server to ask. The identifiers for your database, your tests, and your secret-adjacent tokens never leave the tab.
Questions
Which UUID version should I use?
v4 unless you have a reason not to. It's random, it's the default almost everywhere, and it's what people mean when they just say UUID. Pick v7 if these are going into a database as keys, since the time-ordered prefix keeps the index tidy. v1 is the legacy time-based format, mostly for systems that already expect it.
What's the difference between a UUID and a GUID?
Nothing, really. GUID is Microsoft's name for the same 128-bit identifier. You'll see GUIDs written in uppercase, sometimes wrapped in curly braces, but the value is identical. Flip on Uppercase here if a Windows or .NET tool is fussy about it.
Are v4 UUIDs random enough to actually be unique?
Yes. A v4 carries 122 random bits, so the realistic worry isn't a collision, it's running out of room to store them all first. They're generated with crypto.getRandomValues, the browser's cryptographic random source, not Math.random.
Should I use a UUID as a database primary key?
You can, and plenty of people do. The one catch: random v4 keys scatter inserts all over the index and fragment it. That's the exact problem v7 was designed to fix. Its timestamp prefix means new rows sort to the end, so reach for v7 if write performance matters.
Can I generate UUIDs in bulk?
Yes. Set the count, hit Generate, and you get that many, one per line, up to 10,000. Copy them or download the list as a text file. Handy for seeding a test database or filling a column with sample IDs.