Generate v4 or v7 UUIDs, one or a thousand.
Generated in this tab — nobody else has seen these.
Generates universally unique identifiers — one, or five hundred — in either of the two versions worth using. v4 is entirely random. v7 puts a millisecond timestamp at the front, so identifiers created around the same time sort together.
That difference matters more than it sounds if the identifier is a database primary key. Random v4 keys scatter inserts across the whole index, which fragments it and slows writes as the table grows; v7 keys land next to each other, so the index stays compact. If you are choosing today and your database is the destination, v7 is usually the better answer.
Both are produced with the browser's cryptographic random source, not Math.random — whose output is predictable from previous values and has no place in anything anyone might treat as unguessable.
An identifier that can be generated anywhere without asking the database for the next number, which is what makes distributed writes and offline-first clients possible.
One identifier attached to a request as it crosses services is what turns a pile of logs into a story.
Uploads named by UUID never overwrite each other, however many users pick photo.jpg on the same afternoon.
Generating a few hundred at once is faster than writing a loop, and pasting real UUIDs makes fixtures look like production data.
v4 for a plain random identifier. v7 when it is going into a database index, or whenever having them sort by creation time would be useful.
One up to five hundred. They appear immediately — there is nothing to submit.
Copy takes the whole list; download saves it as a text file, one per line.
Every press produces a fresh set. Your version and count are remembered for next time.
v4 is 122 random bits. v7 replaces the first 48 with a millisecond timestamp and fills the rest with randomness, so the identifiers sort chronologically while staying unique. v7 is the newer standard (RFC 9562) and is generally the better default for database keys.
Not in practice. A v4 has 122 random bits — you would need to generate roughly a billion a second for about 85 years to have a one in a billion chance of a single collision. The risk is not worth designing around.
They are generated from a cryptographic random source, so a v4 is unpredictable. But a UUID is designed to be unique rather than secret, and it is often logged, put in URLs and shared. For anything that grants access, use a purpose-made token instead.
Yes — the timestamp is right there in the first half, by design. That is usually a feature, but it means a v7 in a public URL tells anyone who looks when the record was made.
No. They are produced in this browser tab and never transmitted, which also means nobody else has ever seen them.