UUID in Rust

Rust UUID Generator

In Rust the UUID comes from the uuid crate, and the interesting part is the feature flags — the generators are opt-in.

uuid crateFeature-gatedno_std capable

Version

How many

Uppercase Hyphens Braces { }

Result

Generated locally with the Web Crypto API — nothing leaves your browser.

Generating UUIDs in Rust

Uuid::new_v4() requires the v4 feature, and the randomness comes from getrandom — so it is CSPRNG-backed rather than reproducible. Uuid::now_v7() requires the v7 feature. Turning features off is a real benefit here: a parser that only ever reads existing identifiers can leave both generator features disabled and pull in no randomness at all.
Uuid is Copy, comparable and Hash, so it works as a map key and in a database row struct without ceremony. Display gives the hyphenated lowercase form, and the crate also exposes the byte array and the Uuid::nil() constant for the all-zero value.

How to generate

Press Generate UUID above to mint a value in this browser — nothing is sent anywhere.
Copy one value with Copy, or set How many and use Copy all for a fixture list.
Switch Version if your code needs v7 instead of the v4 default, and turn on Formatting to match your stack's conventions.

Use Cases

Row identifiers in a sqlx or Diesel model, so the ID exists before the insert.
Distributed nodes — no coordinator needed to hand out an identifier.
Test fixtures — generate a set here and paste them into a test module.

How Rust UUID Generator Compares

Uuid::new_v4()	Random, feature "v4", CSPRNG-backed
Uuid::now_v7()	Time-ordered, feature "v7" — best for primary keys
Uuid::new_v5()	Deterministic from a namespace and name, feature "v5"

Code Examples

Cargo.toml

[dependencies]
uuid = { version = "1", features = ["v4", "v7", "serde"] }

Rust

use uuid::Uuid;

fn main() {
    let v4 = Uuid::new_v4();          // random
    let v7 = Uuid::now_v7();          // time-ordered

    println!("{v4}");                // 8f2c7b41-0d3e-4a55-b6c1-8e7d9f0a1b2c
    println!("{v7}");                // 0198c2f1-6d8a-7cc3-9b21-4a7f0e5d3c11

    let parsed: Uuid = "8f2c7b41-0d3e-4a55-b6c1-8e7d9f0a1b2c"
        .parse()
        .expect("valid uuid");
    println!("{}", parsed.as_bytes().len()); // 16
}

Frequently Asked Questions

Why is Uuid::new_v4() not found in Rust?

The generators are behind cargo features. Add features = ["v4"] (or "v7") to the uuid dependency in Cargo.toml.

Is the Rust uuid crate's v4 cryptographically random?

Yes — it draws from getrandom, which uses the operating system entropy source. Use v5 instead when you want the same name to always produce the same value.

How do I serialise a Uuid as a string with serde?

Enable the crate's serde feature. Uuid then serialises as the canonical hyphenated string rather than as a byte array.