UUID Generator
Generate random UUIDs (v4) for development and testing.
About This Tool
Generate cryptographically random UUID v4 identifiers individually or in bulk. Copy a single UUID or generate up to 100 at once for database seeding, API testing, or unique identifier needs. Uses the Web Crypto API for true randomness, producing RFC 4122 compliant UUIDs. All generation happens client-side with nothing stored or transmitted.
What you provide
Number of UUIDs to generate
What you get
One or more UUID v4 strings
How to Use
- Click Generate to create a new UUID instantly.
- Use the bulk slider to generate up to 100 UUIDs at once.
- Click Copy to copy the result to your clipboard.
UUID Version Comparison
| Version | Source | Sortable | Privacy | Best For |
|---|---|---|---|---|
| v1 | MAC address + timestamp | Yes (time-ordered) | Leaks MAC address | Internal systems where sortability matters and privacy is not a concern |
| v4 | Cryptographically random | No | Safe | General-purpose identifiers, API resources, session tokens |
| v5 | Namespace + name + SHA-1 | Deterministic | Safe | Content-addressable IDs where the same input must always produce the same UUID |
| v7 | Unix timestamp + random bits | Yes (time-ordered) | Safe | Database primary keys where index locality and sortability are important |
Choosing the Right UUID Version
For most web applications, UUID v4 is the right default. It requires no input, has no coordination overhead, and its 122 bits of randomness make collisions statistically impossible at any realistic scale. Use it for user IDs, API resource identifiers, session tokens, and anything where you just need a globally unique value with no other constraints.
Where v4 falls short is database performance at scale. Because v4 values are completely random, inserting them as primary keys into a B-tree index causes constant page splits and cache misses — a problem that becomes measurable above a few million rows in MySQL InnoDB or PostgreSQL with a UUID primary key. UUID v7 solves this by embedding a millisecond-precision Unix timestamp in the most significant bits, so new UUIDs sort after older ones. This keeps inserts near the end of the index, preserving locality and dramatically reducing write amplification.
UUID v1 is best avoided in any public-facing context. The inclusion of the generating machine's MAC address means every v1 UUID leaks hardware information that can be used to fingerprint servers or correlate requests. UUID v5 serves a different niche entirely: given the same namespace UUID and the same name string, it always produces the same output. That makes it useful for deduplication, content-addressable storage, and deterministic ID generation in data pipelines where idempotency matters.
Generating UUIDs in Different Languages
Node.js crypto.randomUUID() needs no dependencies from v14.17+. Python's uuid module is stdlib. For v7 in Node.js you need the uuid package. All three produce RFC 4122 compliant strings.
// Node.js 14.17+ — built-in, no dependencies
const id = crypto.randomUUID();
// → 'f47ac10b-58cc-4372-a567-0e02b2c3d479'
// Python 3.x — stdlib uuid module
// import uuid
// id = str(uuid.uuid4())
// → 'f47ac10b-58cc-4372-a567-0e02b2c3d479'
// Go — requires github.com/google/uuid
// import "github.com/google/uuid"
// id := uuid.New().String()
// → 'f47ac10b-58cc-4372-a567-0e02b2c3d479'
// UUID v7 in Node.js (requires uuid@9+)
import { v7 as uuidv7 } from 'uuid';
const sortableId = uuidv7();
// → '018e3a2f-1b6c-7000-8f00-3c7c3c7c3c7c' (time-ordered)Frequently Asked Questions
- What is a UUID?
- A UUID (Universally Unique Identifier) is a 128-bit identifier formatted as 32 hexadecimal characters separated by hyphens (e.g. 550e8400-e29b-41d4-a716-446655440000). UUID v4 uses random numbers, making collisions virtually impossible.
- Are the generated UUIDs truly random?
- Yes. This tool uses the Web Crypto API (crypto.randomUUID or crypto.getRandomValues) for cryptographically secure random generation.
- Can I generate multiple UUIDs at once?
- Yes. Use the bulk slider to generate up to 100 UUIDs in a single click, perfect for database seeding or test data.
- What is the difference between UUID versions?
- UUID v1 uses timestamps and MAC addresses, v3 and v5 use namespace-based hashing (MD5 and SHA-1 respectively), and v4 uses random numbers. Version 4 is the most common for general-purpose unique identifiers because it requires no coordination or input data.
- Will two UUIDs ever be the same?
- In practice, no. A UUID v4 has 122 random bits, giving roughly 5.3 x 10^36 possible values. You would need to generate about 2.7 x 10^18 UUIDs before having a 50% chance of a single collision, which is far beyond any realistic use case.
Learn More
UUID v1 vs v4: Which Should You Use?
Compare UUID v1 and v4 formats with technical details, security implications, and real-world use cases. Includes UUID v7 as a modern alternative.
7 min read