Free UUID v4 Generator & Bulk GUID Creator

Online UUID & GUID v4 Generator: Random 128-Bit Unique Identifiers

A UUID (Universally Unique Identifier) is a standardized 128-bit mathematical value formatted as a 36-character string, designed to provide globally unique keys across distributed computer networks and databases without requiring central server coordination or registration authority.

Universally Unique Identifiers—also referred to as Globally Unique Identifiers (GUIDs) in Microsoft architectures—serve as the foundation of modern distributed computing, distributed tracing, database keys, and message queue transactions. The Urban Mixo UUID Generator creates standardized Version 4 random UUIDs complying strictly with RFC 4122 and updated RFC 9562 standards, executing entirely in client-side browser memory.

Identifier Formats & UUID Versions Comparison

Compare standard unique identifier specifications, entropy mechanics, and architectural use cases:

Identifier Type Core Mechanism Time-Sortable Collision Protection Primary Use Case
UUID v4 122 bits of pseudo-random entropy No (Random) Mathematical probability (2122) API request IDs, session tokens, non-clustered keys
UUID v7 Unix timestamp (ms) + random entropy Yes (Chronological) Timestamp + random bits Modern database clustered primary keys
ULID Timestamp + random entropy (Crockford's Base32) Yes (Lexicographical) 80-bit randomness per millisecond URL-safe, case-insensitive clustered IDs
UUID v1 Timestamp + MAC hardware address Partially Network card address uniqueness Legacy distributed systems (privacy risk)

Anatomy of a Version 4 UUID String

A standard UUID is formatted as a 36-character hexadecimal string separated by four hyphens: 8-4-4-4-12 (e.g., xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx). In a Version 4 implementation:

  • 122 Bits of Cryptographic Entropy: 122 of the 128 total bits are populated using hardware-collected pseudo-random values.
  • Version Nibble (13th Character): The 13th character is hardcoded to 4, identifying it as an RFC 4122/9562 Version 4 random algorithm.
  • Variant Bits (17th Character): The 17th character is reserved for the variant bits (10xx in binary), always beginning with 8, 9, a, or b.

How to Generate UUID v4 in Code (Zero Dependencies)

If you need to generate Version 4 UUIDs programmatically in your microservices or database seeding scripts, use these native, dependency-free implementations:

1. JavaScript (Modern Browsers & Node.js 16+)

// Native Web & Node.js API (Zero npm packages required)
const uuid = crypto.randomUUID();
console.log(uuid);
// Output: "c9a646d3-9c61-4cc9-bc3d-24d187cf5d5d"

2. Python 3

import uuid
Generate a cryptographically random UUID v4

new_id = uuid.uuid4()

print(str(new_id))
Output: "6ba7b810-9dad-11d1-80b4-00c04fd430c8"

3. PHP (Pure PHP — No PECL Extension Required)

<?php
// Standard RFC 4122 / RFC 9562 compliant v4 generator
function generateUUIDv4() {
$data = random_bytes(16);
$data[6] = chr(ord($data[6]) & 0x0f | 0x40); // Set version to 0100 (v4)
$data[8] = chr(ord($data[8]) & 0x3f | 0x80); // Set variant to 10xx
return vsprintf('%s%s-%s-%s-%s-%s%s%s', str_split(bin2hex($data), 4));
}

echo generateUUIDv4();
?>

Frequently Asked Questions

What is the difference between a UUID and a GUID?

There is no structural difference. UUID (Universally Unique Identifier) is the global open standard defined by RFC 4122 and RFC 9562. GUID (Globally Unique Identifier) is Microsoft's implementation of the exact same 128-bit specification used across Windows and .NET environments.

Can two generated UUID v4 values ever collide?

While theoretically possible, the mathematical probability of a duplicate collision among random v4 UUIDs is practically zero. You would need to generate over 1 billion UUIDs per second continuously for roughly 85 years to have a 50% probability of encountering a single duplicate collision.

Why are random UUID v4 values bad for database primary keys?

Because UUID v4 values are completely random, inserting new rows forces database storage engines (like PostgreSQL or MySQL InnoDB) to insert data into random positions across B-Tree index pages. This causes severe index page splits, memory cache thrashing, and degraded write performance. For clustered primary keys, time-ordered identifiers like UUID v7 or ULID are recommended.

Are these UUIDs generated on a server?

No. Generation takes place locally inside your browser runtime utilizing native crypto.randomUUID() and crypto.getRandomValues(). Generated IDs are never logged, cached, or transmitted over an API.

Related Architecture & Database Guides