UUID Generator
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- 100% Free
- Zero Server Data
Make one identifier or a thousand, in the two versions worth using. Version 4 is 122 random bits and is what most people mean by a UUID. Version 7 begins with the millisecond it was made, so rows keyed by one sort and land together in an index instead of scattering across it, which is the difference that shows up as a slow table two years later. The randomness comes from your operating system, never from a formula, and nothing is generated on a server.
Version 4 is the familiar one. Version 7 starts with the timestamp, so a batch stays in order and a database index stays compact.
Frequently asked questions
When should I use version 7 instead of version 4?
When the identifier is a primary key. A version 4 is random, so consecutive inserts land in unrelated places in the index and the index stops fitting the pattern a database is fast at. A version 7 begins with the time, so new rows sort together and land together. For an identifier that is never indexed, the two are equivalent.
Are these unique?
To the extent that anything is. A version 4 has 122 random bits, which is enough that generating a billion a second for a century leaves the chance of a collision far below the chance of the hardware being wrong. The bits come from the operating system generator, not from Math.random, which is predictable and has no business anywhere near an identifier.
Are they generated on your server?
No, and this is the reason to prefer a local tool for this job. They are made in this tab by your own machine. The site’s security policy sets connect-src ‘none’, so the browser blocks network requests from these pages, so an identifier could not be sent even if the code tried, which matters because a UUID from a website is a UUID that website has seen.
Why the option to remove the dashes?
Because some systems store a UUID as 32 characters rather than 36, and pasting the dashed form into one of them is a small daily annoyance. The value is identical either way.