Generate UUIDs (also called GUIDs) in your browser. Choose version 4 for fully random IDs or version 7 for IDs that start with a timestamp and sort in the order they were made, pick how many you need, and set the format: upper case, with or without hyphens, with or without braces. Nothing is sent anywhere.
Every UUID is 16 bytes. In a version 4 UUID almost all of them are random, with a few bits overwritten to mark the version (4) and the variant (the first digit of the fourth group is 8, 9, a or b). That makes v4 the easiest choice when all you need is a unique label with no meaning inside it.
Version 7 puts the time first: the first 48 bits are the Unix time in milliseconds, then come the version bits, a counter and random bits. Because the time leads, sorting v7 IDs as text or bytes sorts them by creation time. This generator advances the counter for IDs made in the same millisecond, so a batch comes out in strictly increasing order.
Random v4 IDs are fine for most things, but in a large table with an index on the ID column they scatter new rows across the whole index, which can slow down writes. Time-ordered v7 IDs append near the end, much like an auto-incrementing number, while still being unique across machines. That is the main reason people switch.
The cost of v7 is that the ID leaks its creation time to anyone who sees it. If that matters, for example in public URLs where you do not want to reveal when an account was made, stay with v4. Also check that your database orders its UUID type the way you expect: SQL Server, for one, compares uniqueidentifier values in an unusual byte order, so a v7 value does not sort by time there.
A UUID is a 128-bit identifier written as 32 hexadecimal digits in five groups, like 123e4567-e89b-42d3-a456-426614174000. It is built so that you can generate IDs on any machine without asking a central server and still be extremely unlikely to ever produce the same one twice.
Version 4 is 122 random bits plus 6 fixed bits for version and variant. Version 7 starts with a 48-bit Unix timestamp in milliseconds, followed by a 12-bit counter and 62 random bits, so later IDs sort after earlier ones. In both, the 13th hex digit is the version number, 4 or 7.
Yes for practical purposes. GUID is the name used by Microsoft tools, including SQL Server and .NET. The format is the same 128-bit value, and the braces and upper case options help you match the style those tools show.
In theory yes, in practice almost never. With 122 random bits in version 4, you would need to generate about a billion UUIDs every second for roughly 85 years to reach even a 50 percent chance of one repeat. Version 7 adds a counter so IDs made in the same millisecond in one batch stay in order and distinct.
They are made in your browser with its cryptographically secure random number generator. Nothing is uploaded or stored by this page.
Related: API key generator, JSON generator, Hex converter.
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