How to Generate a UUID in JavaScript, Python, and SQL

In JavaScript, call crypto.randomUUID() — built into every modern browser and Node.js, no library required. In Python, uuid.uuid4() from the standard library. In PostgreSQL, gen_random_uuid() as a column default. All three generate a cryptographically random v4 UUID with no setup.

JavaScript

const id = crypto.randomUUID();
// e.g. "3fa85f64-5717-4562-b3fc-2c963f66afa6"

crypto.randomUUID() has been available in browsers and Node.js for years now and needs no import in the browser. One real constraint: it only works in a secure context (HTTPS or localhost) — calling it from a plain HTTP page will throw. For older environments, crypto.getRandomValues() can generate the same v4 format manually.

Python

import uuid
id = str(uuid.uuid4())
# e.g. "3fa85f64-5717-4562-b3fc-2c963f66afa6"

Python's uuid module is part of the standard library — no pip install needed. uuid4() generates a random v4 UUID; the module also supports uuid1() (MAC address plus timestamp based, rarely what you want for public-facing IDs) if you specifically need that variant.

SQL

CREATE TABLE users (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  email VARCHAR(255) NOT NULL
);

PostgreSQL's gen_random_uuid() (built in since Postgres 13) generates a v4 UUID as a column default, so every insert gets one automatically without application code needing to generate it. Older Postgres versions need the pgcrypto extension enabled first; MySQL uses UUID() instead, which — worth noting — generates a v1 (timestamp-based) UUID by default, not v4.

The one thing all of these have in common

Every method above draws from a cryptographically secure random source, not a predictable one — that matters if these IDs will ever be exposed publicly, since a guessable generation scheme can leak information about ordering or volume. If you need the IDs to also sort by creation time, look at UUID v7 instead of v4 specifically.