UUID Generator
Generate universally unique identifiers (UUIDs) v4. Perfect for database IDs and unique keys.
About UUIDs
UUID v4: Randomly generated 128-bit identifier
Format: 8-4-4-4-12 hexadecimal digits
Example: 550e8400-e29b-41d4-a716-446655440000
Common Uses
- • Database primary keys
- • Session identifiers
- • File names
- • API request IDs
- • Distributed systems
Quick Stats
Collision Probability: Virtually zero
Total Possible: 2122 ≈ 5.3 × 1036
Generation: Cryptographically random
Complete Guide to UUIDs for Developers
What Are UUIDs and Why Use Them?
A UUID (Universally Unique Identifier) is a 128-bit identifier designed to be globally unique without requiring a central coordinating authority. Unlike sequential database IDs (1, 2, 3...), UUIDs can be generated independently by any system anywhere in the world and are virtually guaranteed to never collide.
This makes UUIDs essential for modern distributed systems, microservices architectures, and applications that need to generate identifiers before communicating with a database. They're used by companies like AWS, Google, and Microsoft throughout their infrastructure.
The randomness of UUID v4 also provides a security benefit: unlike sequential IDs, attackers can't easily guess or enumerate valid identifiers in your system.
UUID v4: The Developer's Choice
There are five UUID versions (v1-v5), plus newer versions like v6 and v7. UUID v4 is the most widely used because it's:
- Truly Random: 122 bits of cryptographic randomness
- Privacy-Safe: No MAC address or timestamp leakage (unlike v1)
- Simple: No input required, just generate and use
- Universal: Supported in every programming language
With 5.3 × 10^36 possible combinations, you could generate 1 billion UUIDs per second for 100 years and still have virtually zero chance of collision.
UUID Versions Comparison
| Version | Generation Method | Pros | Cons | Best For |
|---|---|---|---|---|
| v1 | Timestamp + MAC address | Sortable by time | Exposes MAC/time | Legacy systems |
| v4 | Random | Simple, secure, private | Not sortable | Most use cases ✓ |
| v5 | SHA-1 hash of namespace + name | Deterministic, reproducible | Requires input | URL-based IDs |
| v7 | Timestamp + random | Sortable + random | Newer, less support | Database indexes |
Understanding UUID Format
550e8400-e29b-41d4-a716-446655440000Format: 8-4-4-4-12 hexadecimal digits (36 characters with hyphens)
Version digit (4): Indicates UUID v4 (random)
Variant digit (a): Indicates RFC 4122 variant (values: 8, 9, a, or b)
Other digits: Random hexadecimal values (0-9, a-f)
Without hyphens: 550e8400e29b41d4a716446655440000 (32 characters)
UUID in Different Languages
import { v4 as uuidv4 } from 'uuid';
const id = uuidv4();import uuid
id = str(uuid.uuid4())SELECT gen_random_uuid();import "github.com/google/uuid"
id := uuid.New().String()🔒 Cryptographically Secure Generation
Our UUID generator uses your browser's built-in cryptographically secure random number generator (CSPRNG) via the Web Crypto API. This ensures truly random, unpredictable UUIDs suitable for security-sensitive applications. All generation happens locally—no UUIDs are transmitted or stored.
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Frequently Asked Questions
What is a UUID and how is it different from other IDs?
A UUID (Universally Unique Identifier) is a 128-bit number designed to be globally unique without requiring a central coordinating authority. Unlike auto-incrementing database IDs (1, 2, 3...), UUIDs can be generated independently by any system and are virtually guaranteed to be unique. This makes them ideal for distributed systems, merging databases, and scenarios where you can't rely on a central ID generator.
What is UUID v4 and why is it the most commonly used version?
UUID v4 is the randomly generated version of UUID, using cryptographically secure random numbers. It's the most popular because: 1) It's simple—no MAC address or timestamp required, 2) It's secure—doesn't leak information about when or where it was created, 3) It's truly random—no predictable patterns. With 122 random bits, the chance of collision is astronomically low (1 in 2^122).
What is the probability of UUID collision?
The probability of generating two identical UUID v4s is approximately 1 in 5.3 × 10^36 (that's 5.3 trillion trillion trillion). To have a 50% chance of collision, you'd need to generate about 2.71 quintillion UUIDs. At 1 billion UUIDs per second, this would take over 85 years. For practical purposes, collisions are considered impossible.
Should I use UUIDs or auto-incrementing IDs for my database?
Use UUIDs when: you need to merge data from multiple databases, generate IDs before inserting into the database, work in distributed systems, or want to hide the number of records. Use auto-incrementing IDs when: performance is critical (UUIDs are larger and slower for indexing), you need human-readable IDs, or storage space is a concern. Many modern applications use UUIDs as public identifiers with internal auto-increment IDs for joins.
What is the UUID format and what do the sections mean?
UUID format is 8-4-4-4-12 hexadecimal digits: xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx. The "M" position indicates the version (4 for v4). The "N" position indicates the variant (8, 9, A, or B for RFC 4122 UUIDs). In UUID v4, all other characters are random hexadecimal digits (0-9, a-f). The hyphens are optional and just improve readability.
Is it safe to expose UUIDs in URLs or APIs?
UUID v4 is generally safe to expose because it's randomly generated and doesn't leak information. However, UUIDs are not secrets—don't use them as the sole authentication mechanism. For sensitive resources, combine UUIDs with proper access control. Avoid UUID v1, which contains MAC addresses and timestamps that could leak information.
Can I use UUIDs with UUID v7 or other newer versions?
UUID v7 is a newer standard that combines timestamp ordering with randomness, making it more efficient for database indexing while maintaining uniqueness. It's gaining adoption but not yet as widely supported as v4. For most use cases, v4 remains the safe choice. Our generator uses v4 for maximum compatibility and true randomness.
Why would I need to generate multiple UUIDs at once?
Bulk UUID generation is useful for: batch importing records to a database, pre-generating IDs for offline-capable applications, creating test datasets, seeding data for development environments, or generating unique identifiers for file systems. Our tool generates up to 1,000 UUIDs instantly, which you can copy and use in your application.
UUIDs in Modern Software Architecture
In today's world of microservices, distributed databases, and cloud-native applications, UUIDs have become indispensable. They solve the fundamental problem of generating unique identifiers without coordination between services—critical for scalability and resilience.
Whether you're building REST APIs, GraphQL services, event-driven systems, or mobile applications, UUIDs provide a reliable foundation for identifying resources across your entire stack. Many modern frameworks and ORMs (like Django, Rails, and Prisma) now default to UUID primary keys.
This generator provides instant, cryptographically secure UUID v4 generation right in your browser. Combined with our other developer tools, you have everything needed for modern application development—all privacy-first and entirely client-side.