developer desk · uuid generator
UUIDs, and the time inside them.
Make v7 or v4 UUIDs, one or a batch. Paste any UUID to read its version — and, for v1, v6 and v7, the moment it was made. Generated in this tab with the browser’s own cryptographic random source.
A v7 batch sorts in the order it was made, even inside one millisecond: the spare bits count up rather than repeat the random draw.
Once you have your ids
To fingerprint a file or a string instead, the hash generator does SHA-256 in the same tab.
Hash text or a fileQuestions
Should I use v7 or v4?
v7 for anything stored in a database index: it starts with a timestamp, so new rows land at the end of the index instead of anywhere in it. v4 when the id must not reveal when it was made — a v7 tells anybody who reads it the millisecond it was created.
Are these UUIDs unique?
A v4 has 122 random bits and a v7 has 74 alongside its timestamp, drawn from the browser’s cryptographic random source. A collision is not something that happens in practice. Inside one batch, v7 ids are also strictly increasing.
Why does my v4 UUID show no time?
Because it has none: every bit except the version and variant is random. Only v1, v6 and v7 carry a clock, and those are the ones this page reads a time from.