How to Generate a UUID: Online, CLI, Python, JavaScript, and SQL

Generating UUIDs is a one-liner in every major language and on the command line. This guide covers the canonical approach in each environment.

Online

uuidgen.io generates UUIDs in your browser. Options include v4 (random), v7 (time-ordered), and batch generation.

Command line

Linux/macOS — built-in uuidgen:

# UUID v4 (random)
uuidgen

# Lowercase (macOS default is uppercase)
uuidgen | tr '[:upper:]' '[:lower:]'

# Generate 10 UUIDs
for i in {1..10}; do uuidgen; done

Python one-liner:

python3 -c "import uuid; print(uuid.uuid4())"

# Multiple UUIDs
python3 -c "import uuid; [print(uuid.uuid4()) for _ in range(10)]"

Node.js one-liner:

node -e "console.log(crypto.randomUUID())"

Python

import uuid

# UUID v4 (random) — most common
uid = uuid.uuid4()
print(uid)           # 550e8400-e29b-41d4-a716-446655440000
print(str(uid))      # same, as string
print(uid.hex)       # "550e8400e29b41d4a716446655440000" (no hyphens)
print(uid.int)       # 113059749145936325402354257176981405696 (integer)
print(uid.bytes)     # b'\x55\x0e...' (16 bytes, binary)

# UUID v1 (time-based, includes MAC address)
uid_v1 = uuid.uuid1()

# UUID v3 (name-based, MD5)
uid_v3 = uuid.uuid3(uuid.NAMESPACE_URL, "https://example.com")

# UUID v5 (name-based, SHA-1 — preferred over v3)
uid_v5 = uuid.uuid5(uuid.NAMESPACE_URL, "https://example.com")

# Parse a UUID string
parsed = uuid.UUID("550e8400-e29b-41d4-a716-446655440000")
# Also accepts without hyphens:
parsed2 = uuid.UUID("550e8400e29b41d4a716446655440000")

# Validate (catches invalid UUIDs)
def is_valid_uuid(s: str) -> bool:
    try:
        uuid.UUID(s)
        return True
    except ValueError:
        return False

JavaScript / Node.js

// Browser / Node.js 19+ / Deno — built-in Web Crypto API
const uid = crypto.randomUUID();
// "550e8400-e29b-41d4-a716-446655440000"

// Node.js all versions: crypto module
const { randomUUID } = require('crypto');
const uid = randomUUID();

// npm: uuid package (more control, UUID v1/v3/v4/v5/v7)
import { v4 as uuidv4, v7 as uuidv7 } from 'uuid';
const uid_v4 = uuidv4();
const uid_v7 = uuidv7();  // time-ordered

// Validate a UUID string
import { validate, version } from 'uuid';
validate("550e8400-e29b-41d4-a716-446655440000");  // true
version("550e8400-e29b-41d4-a716-446655440000");   // 4

Go

package main

import (
    "fmt"
    "github.com/google/uuid"
)

func main() {
    // UUID v4
    id := uuid.New()
    fmt.Println(id.String())

    // UUID v7 (time-ordered)
    id7, err := uuid.NewV7()
    if err != nil { panic(err) }
    fmt.Println(id7.String())

    // Parse
    parsed, err := uuid.Parse("550e8400-e29b-41d4-a716-446655440000")
    if err != nil { panic(err) }

    // Generate and get bytes
    id = uuid.New()
    bytes := id[:]  // [16]byte slice
}

SQL — database-native UUID generation

PostgreSQL:

-- PostgreSQL 13+ (recommended)
SELECT gen_random_uuid();

-- pgcrypto extension (older PostgreSQL)
SELECT uuid_generate_v4();  -- requires: CREATE EXTENSION IF NOT EXISTS "uuid-ossp";

-- UUID as default primary key
CREATE TABLE users (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    email TEXT NOT NULL UNIQUE
);

-- UUID v7 (monotonic, good for PKs) — available via pg_uuidv7 extension
SELECT uuid_generate_v7();

MySQL 8.0+:

-- UUID v1
SELECT UUID();

-- UUID v4 equivalent (MySQL doesn't natively have v4, but UUID() is fine for most uses)
-- For truly random UUID, generate in application code

-- UUID as primary key
CREATE TABLE users (
    id CHAR(36) PRIMARY KEY DEFAULT (UUID()),
    email VARCHAR(255) NOT NULL UNIQUE
);

SQLite:

-- SQLite doesn't have a built-in UUID function.
-- Generate in application code and insert as TEXT.

CREATE TABLE users (
    id TEXT PRIMARY KEY NOT NULL,
    email TEXT NOT NULL UNIQUE
);
-- Insert: INSERT INTO users (id, email) VALUES (?, ?) with uuid in application

UUID v7 (time-ordered) in code

UUID v7 is the recommended version for database primary keys — it sorts chronologically and avoids B-tree index fragmentation:

# Python: using uuid7 package
# pip install uuid7
import uuid7
uid = uuid7.uuid7()
print(uid)  # 017f22e2-79b0-7cc3-98c4-dc0c0c07398f

// npm: uuid package
import { v7 as uuidv7 } from 'uuid';
const uid = uuidv7();

id, _ := uuid.NewV7()

The first 48 bits of UUID v7 are the Unix timestamp in milliseconds, so UUIDs generated later sort after UUIDs generated earlier.

Generate UUIDs at uuidgen.io.