About this tool
A UUID (Universally Unique Identifier) is a 128-bit value written as 32 hexadecimal digits in the canonical 8-4-4-4-12 layout. This generator produces version 4 UUIDs, which fill 122 bits with cryptographically random data from the Web Crypto API, and version 7 UUIDs from RFC 9562, which prepend a 48-bit big-endian Unix-millisecond timestamp before the random bits so the identifiers sort chronologically. Both set their version and variant bits manually per the spec.
Use it to seed database primary keys, correlation and request IDs, idempotency keys, or test fixtures. Reach for v7 when you want time-sortable keys that keep B-tree indexes compact and avoid the page-split churn random v4 keys cause; reach for v4 when you only need uniqueness with no ordering signal. Generate up to 500 at once, copy them as a newline-separated list, and toggle uppercase, hyphen-free, or quoted output to paste straight into SQL, JSON, or code.
Every UUID is generated in your browser with crypto.getRandomValues — none are sent to or logged by any server.
Frequently asked questions
What is the difference between UUID v4 and UUID v7?
v4 is fully random (122 random bits), so values are unpredictable but unordered. v7 starts with a 48-bit Unix-millisecond timestamp followed by random bits, so values generated later sort after earlier ones — useful for database keys that index efficiently.
Are UUID v4 values guaranteed to be unique?
Not guaranteed, but the collision probability is negligible: with 122 random bits you would need to generate billions of UUIDs before a duplicate becomes statistically likely. For practical purposes they are treated as unique.
Is UUID v7 safe to use as a database primary key?
Yes, and it is often better than v4 for that purpose. Because v7 is time-ordered, sequential inserts append to the end of a B-tree index instead of scattering across it, reducing page splits and keeping indexes more compact.