UUID Generator
Free UUID generator — create v4 random, v7 time-ordered, or deterministic v3/v5 UUIDs in your browser, one at a time or hundreds at once. Generated by a Rust CSPRNG compiled to WebAssembly; nothing is uploaded.
Runs entirely in your browser — nothing you enter is uploaded or stored.
Generating UUIDs
A UUID is 128 bits laid out as xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx, whereM is the version and the top bits of N are the variant. What fills the rest depends on the version, and that choice has real consequences for how the identifiers behave in a database.
v4 versus v7
v4 is 122 random bits. It is perfectly unique and perfectly unsortable — consecutive inserts land in random places in an index, which fragments B-trees and hurts write throughput on large tables. v7 puts a 48-bit Unix millisecond timestamp in the high bits, so newly generated values sort after older ones and inserts stay at the right-hand edge of the index. If you are choosing a primary key type today, v7 is usually the better default.
Deterministic UUIDs
v3 and v5 hash a namespace UUID together with a name, so the same inputs always yield the same output. That is useful for deriving a stable identifier from something you already have — a domain, a URL, a file path — without storing a mapping table.
Frequently asked questions
Which UUID version should I use?
v4 for general-purpose identifiers, v7 for database primary keys. v7 embeds a millisecond timestamp in its high bits, so a B-tree index on it stays sequential instead of scattering writes across the whole index the way v4 does. Use v5 when you need the same input to always produce the same UUID.
What is the difference between v3 and v5?
Both hash a namespace and a name into a deterministic UUID. v3 uses MD5 and v5 uses SHA-1. Prefer v5 — neither hash is used in a way that requires collision resistance here, but there is no reason to pick the more broken one.
Can two v4 UUIDs collide?
In principle yes, in practice no. 122 random bits means you would need to generate roughly 2.7×10^18 of them before a 50% chance of any collision. The realistic risk is not the maths but a weak random source — this tool uses a CSPRNG, not Math.random.
Are these generated on a server?
No. Every UUID is produced locally by a WebAssembly build of the Rust uuid crate, seeded from the browser CSPRNG. Nothing is transmitted.