GUID / UUID Generator

What is a GUID / UUID?

A GUID (Globally Unique Identifier) - also known as a UUID (Universally Unique Identifier) - is a 128-bit number standardized by RFC 4122. It is designed to be unique across space and time without requiring a central authority to coordinate assignment.

The most common format is a string of 32 hexadecimal digits, displayed in 5 groups separated by hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. This results in 2¹²² possible values - approximately 5.3 × 10³⁶ - making collisions practically impossible.

Common Uses for GUIDs

• Database primary keys - unique row identifiers in SQL and NoSQL databases
• Session tokens - user session IDs in web applications
• API keys - unique identifiers for API access control
• File names - collision-free temporary and uploaded file names
• Message IDs - unique message tracking in queuing systems (RabbitMQ, Kafka)
• Software component IDs - COM class identifiers in Windows (CLSID, IID)
• Correlation IDs - request tracing across microservices

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UUID v4 vs Other UUID Versions

Version	Generation method	Best for
v4	Cryptographically random	General purpose, database keys, tokens
v1	Time + MAC address	When monotonic ordering is needed (leaks host identity)
v3	Name + MD5 hash	Deterministic IDs from a namespace
v5	Name + SHA-1 hash	Deterministic IDs (preferred over v3)
v7	Unix timestamp + random	Time-ordered keys (database index-friendly)

UUID v4 is the recommended default for the vast majority of use cases. It is generated entirely from random numbers, requires no additional input, and reveals nothing about the host or timestamp.

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GUID Output Format Guide

This tool generates GUIDs in five formats. Choose the right one for your environment:

Format	Example	When to use
Standard	550e8400-e29b-41d4-a716-446655440000	Default - most databases, APIs, logs
No Hyphens	550e8400e29b41d4a716446655440000	URLs, compact storage, some ORMs
With Braces	{550e8400-e29b-41d4-a716-446655440000}	C#, .NET, COM, Windows Registry
Uppercase	550E8400-E29B-41D4-A716-446655440000	Legacy systems, case-sensitive comparisons
Uppercase No Hyphens	550E8400E29B41D4A716446655440000	Compact uppercase storage

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How to Generate a GUID in Code

Most modern languages have built-in UUID v4 support - you only need an online generator for quick one-off values or bulk exports.

JavaScript / Node.js

// Browser
const id = crypto.randomUUID(); // built-in, no library needed

// Node.js 14.17+
import { randomUUID } from 'crypto';
const id = randomUUID();

Python

import uuid
id = str(uuid.uuid4())  # e.g. '550e8400-e29b-41d4-a716-446655440000'

C# / .NET

Guid id = Guid.NewGuid();
string formatted = id.ToString(); // standard format
string braces   = id.ToString("B"); // {550e8400-...}
string noHyphens = id.ToString("N"); // no hyphens

SQL Server

SELECT NEWID(); -- e.g. 550E8400-E29B-41D4-A716-446655440000

PostgreSQL

SELECT gen_random_uuid(); -- requires pgcrypto or PostgreSQL 13+

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Are GUIDs Cryptographically Secure?

Yes - UUID v4 generated by this tool uses the browser's Web Crypto API (crypto.randomUUID()), which produces cryptographically secure random numbers. This means:

• The output is unpredictable - no one can guess the next GUID from previous ones
• No server involved - generation happens entirely in your browser
• Suitable for use as session tokens, nonces, and API identifiers

Note: GUIDs are not passwords. They are long and random, but they are also public identifiers. Do not use a raw GUID as a secret unless you store it securely.

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GUID Collision Probability

With 2¹²² possible UUID v4 values (~5.3 × 10³⁶), collisions are astronomically unlikely:

• Generating 1 billion GUIDs per second for 85 years gives only a 50% chance of one collision
• For practical purposes, UUIDs are considered globally unique without any coordination

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GUID vs UUID: What is the Difference?

Nothing fundamental. GUID is Microsoft's term (used in Windows, .NET, COM); UUID is the IETF term from RFC 4122. Both refer to the same 128-bit identifier format. The two terms are fully interchangeable in technical contexts.

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Using GUIDs as Database Primary Keys

GUIDs are popular as database primary keys because they are:

• Globally unique - safe to merge data from multiple databases or clients
• Generated client-side - no round-trip to the database to get a new ID
• Non-sequential - harder to enumerate records by ID

Trade-off: Random GUIDs (v4) cause index fragmentation in B-tree indexes because inserts land at random positions. Solutions include:

• Use UUID v7 (time-ordered) for new projects with high-write workloads
• Use NEWSEQUENTIALID() in SQL Server instead of NEWID()
• Use gen_random_uuid() with uuid_generate_v1mc() as an index-friendly alternative in PostgreSQL

For most applications, the convenience of UUID v4 outweighs the index performance concern.