UUID Generator (v4 and v7)
Generate up to a thousand UUIDs at once. Version 4 is fully random; version 7 embeds a timestamp so the ids sort in creation order - much friendlier to database indexes.
v4: random, and the safe default
A version 4 UUID carries 122 bits of randomness from the browser's cryptographic generator. The chance of two ever colliding is negligible even across independent systems, which is exactly why it is the default choice for identifiers created in more than one place.
v7: sortable, and better for databases
A version 7 UUID begins with a 48-bit Unix millisecond timestamp, so ids generated later sort after ids generated earlier. That locality keeps B-tree indexes compact and inserts fast, avoiding the write amplification that random v4 primary keys cause in MySQL and PostgreSQL. It also means the creation time is readable from the id.
Formatting for the target system
Uppercase, hyphen-free and brace-wrapped forms are all the same 128-bit value written differently. Windows tooling and the .NET `Guid` type favour braces; some databases store the 32-character hex form. Pick the shape your target expects and copy the whole batch at once.
Frequently asked questions
Are these generated on a server?
No. Nothing you paste leaves your browser. The page loads a small amount of JavaScript, and every calculation happens on your own machine - there is no server to send data to. The ids come from your browser's own cryptographic random number generator, which means they are never transmitted, logged or reused by anyone else.
Are they truly unique?
Not guaranteed by mathematics, but safe in practice. With 122 random bits you would need to generate billions of v4 UUIDs before a collision became remotely likely. For every realistic workload, treating them as unique is correct.
Should I use v4 or v7 for a primary key?
Prefer v7. Random v4 keys scatter inserts across the whole index, which fragments B-trees and hurts write throughput on large tables. v7 keeps recent rows together. Use v4 when you specifically do not want creation time to be inferable from the id.
Is a UUID secret?
Treat it as an identifier, not a credential. A v4 UUID is unguessable enough to be used as an unlisted URL, but it may end up in logs, referrer headers and browser history. Anything that needs real protection needs an actual authentication check.