UUID Generator

Generate random UUIDs (v1, v4, v7). Create unique identifiers for your applications.

UUID Version

Count

Code Examples

// Native crypto API (UUID v4)
const uuid = crypto.randomUUID();

// Using uuid library
// npm install uuid
import { v4 as uuidv4, v1 as uuidv1 } from 'uuid';
const id = uuidv4();  // Random
const id1 = uuidv1(); // Time-based

What is a UUID?

A UUID (Universally Unique Identifier) is like a digital fingerprint - a 128-bit number that's virtually guaranteed to be unique across all computers, all time, everywhere in the universe.

It looks like this: 550e8400-e29b-41d4-a716-446655440000

Why do we need them?

Create unique IDs without a central authority
Merge databases without ID conflicts
Generate IDs offline that stay unique when synced
Track objects across distributed systems

Think of UUIDs as license plates for data - each one is unique, and you don't need to ask anyone's permission to create one.

UUID Versions Explained

Version	Based On	Best For
v1	Timestamp + MAC address	Time-ordered records
v4	Random numbers	Most common, general use
v5	Namespace + name (SHA-1)	Reproducible IDs from names
v7	Timestamp + random (new!)	Database-friendly, sortable

Version 4 (Random) - Most Popular

f47ac10b-58cc-4372-a567-0e02b2c3d479
         ↑
    "4" indicates version 4

Uses cryptographically secure random numbers. The chance of collision is astronomically low.

Version 1 (Time-based) Encodes the current timestamp and your computer's MAC address. Useful when you need to know when a UUID was created.

Version 7 (Newest, 2022) Combines timestamp with randomness. Perfect for databases because UUIDs are sortable by creation time!

How Unique Are UUIDs Really?

🎲 The Math Behind Uniqueness

UUID v4 has 122 random bits, giving us 2^122 possible combinations: 5,316,911,983,139,663,491,615,228,241,121,400,000 unique UUIDs

To have a 50% chance of collision:

Generate 2.71 × 10^18 UUIDs
At 1 billion UUIDs per second, this takes 86 years!

Real-world perspective:

If every person on Earth generated 1 UUID per second
For 100 years straight
The collision probability would still be less than 0.00000001%

For all practical purposes, you can treat UUID v4 as unique. No coordination needed, no database lookups - just generate and use!

Anatomy of a UUID

550e8400-e29b-41d4-a716-446655440000
│        │    │    │    │
│        │    │    │    └── Node (48 bits)
│        │    │    └── Clock sequence (14 bits)  
│        │    └── Version (4 bits) + Time high
│        └── Time mid (16 bits)
└── Time low (32 bits)

The 8-4-4-4-12 Format

32 hex characters
5 groups separated by hyphens
128 bits total (4 bits per hex character)

Version Indicator The 13th character tells you the version:

1 = Time-based (v1)
4 = Random (v4)
7 = Unix timestamp (v7)

When to Use UUIDs

✅ Perfect for:

Database primary keys (especially distributed systems)
API resource identifiers
Session tokens
File names for uploads
Tracking IDs across microservices

⚠️ Consider alternatives when:

You need human-readable IDs (use short codes instead)
Storage space is critical (UUIDs are 16 bytes)
You need strictly sequential IDs (use auto-increment)
URL aesthetics matter (UUIDs are long and ugly)

💡 Pro Tips:

Store as binary (16 bytes) not string (36 bytes) in databases
Use UUID v7 for better database index performance
Never expose UUIDs that could leak timing information

UUID vs Alternatives

ID Type	Length	Sortable	Collision-Free	Example
UUID v4	36 chars	❌	Practically	`f47ac10b-58cc-...`
UUID v7	36 chars	✅	Practically	`018e4c8b-...`
ULID	26 chars	✅	Practically	`01ARZ3NDEKTSV4...`
NanoID	21 chars	❌	Configurable	`V1StGXR8_Z5jdHi6B`
Snowflake	19 digits	✅	Guaranteed*	`1541815603606036480`

*Snowflake IDs require coordination (machine ID assignment)