UUID Generator
Generate random v4 or time-sortable v7 UUIDs, one at a time or in bulk.
GeneratorsWhat a UUID is for
A UUID is a 128-bit identifier built to be unique without a central authority assigning it. That is its whole purpose: two systems that never talk to each other can generate identifiers without risking a collision, which a counter cannot do.
v4 and v7: the difference that matters
Version 4 is entirely random. Version 7 puts the creation time first, so two UUIDs created at different moments sort themselves. The difference shows up in the database: used as a primary key, v4 scatters writes across the whole index and fragments it, while v7 concentrates them at the end, as a counter would. On large tables that is a measurable performance difference.
When v7 is the wrong choice
Precisely because it embeds the time, a v7 reveals when it was created. If the identifier is public and that moment is something you would rather not disclose — when a user signed up, when an order was placed — v4 remains the right pick.
Collisions
A v4 UUID has 122 random bits. The chance of generating the same one twice stays negligible even after billions of draws, provided the random source is good — which is why this tool uses the browser's cryptographic source rather than an ordinary random function.
How to use it
Pick the version, how many rows you need — from one to five hundred — and generate: the identifiers appear in the list, ready to copy. Every generation happens in the browser with the cryptographic random source and involves no server at all.
UUID and GUID
They are the same identifier: GUID is the name Microsoft gave it, UUID the
standard's, described by RFC 4122 and updated by RFC 9562, which introduced
version 7. The form produced here is the canonical one: hexadecimal groups of
8-4-4-4-12 digits separated by hyphens, as in
550e8400-e29b-41d4-a716-446655440000.
Where they turn up in practice
As the resource identifier in REST APIs, in distributed systems where no node can coordinate the others, in temporary file names that must not overwrite one another, and in trace identifiers that follow a request across several services to keep the whole journey tied together.
Frequently asked questions
v7 if the identifier becomes a database key, because it does not fragment the index. v4 if the identifier is public and you do not want it revealing when it was created.
They use the browser's cryptographic random source, the same one used for security operations. They are never transmitted or stored anywhere.
With the SmartTools UUID Generator: pick the version — fully random v4 or time-sortable v7 — and generate one or many identifiers with one click, ready to copy. It uses the browser's cryptographic random source, is free and requires no registration.