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# How to Generate UUID v4 in Node.js, Python, and Go

UUID v4 (Universally Unique Identifier, version 4) is the go-to format for generating unique identifiers without central coordination. With 122 bits of randomness, the probability of collision is negligible for any practical application.

A UUID v4 looks like this:

```
9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d
```

It follows the format: 8-4-4-4-12 hexadecimal characters separated by hyphens. The "4" in the third group indicates the version, and the first digit of the fourth group (8, 9, a, or b) indicates the variant.

## Node.js

Since Node.js 14.17.0, `crypto.randomUUID()` is available natively — no package required:

```javascript
const { randomUUID } = require('crypto');

const id = randomUUID();
console.log(id); // '9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d'

// In ESM / modern Node.js
import { randomUUID } from 'crypto';
const id = randomUUID();
```

For older Node.js or browser environments, or when you need v1/v5 support, use the `uuid` package:

```javascript
const { v4: uuidv4 } = require('uuid');
const id = uuidv4();
```

## Python

Python's standard library includes the `uuid` module — no installation needed:

```python
import uuid

# Generate a UUID v4
id = uuid.uuid4()
print(str(id))       # '9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d'
print(id.hex)        # '9b1deb4d3b7d4bad9bdd2b0d7b3dcb6d' (no hyphens)
print(int(id))       # 128-bit integer representation

# As a string directly
id_str = str(uuid.uuid4())
```

## Go

Install the `github.com/google/uuid` package (the de facto standard in Go):

```bash
go get github.com/google/uuid
```

```go
package main

import (
    "fmt"
    "github.com/google/uuid"
)

func main() {
    // Generate v4 UUID
    id := uuid.New()
    fmt.Println(id.String()) // '9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d'

// Or using NewRandom() with error handling
    id, err := uuid.NewRandom()
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(id)
}
```

## When to Use UUID vs Other ID Formats

| Use Case | Recommendation |
|----------|---------------|
| Database primary key (single DB) | Auto-increment (simpler, sortable) |
| Distributed system / generated client-side | UUID v4 |
| Deterministic from input | UUID v5 |
| Sortable, time-ordered IDs | ULID or UUID v7 (draft) |
| Short public IDs | Nanoid or Base62-encoded UUID |

For most web applications generating database records server-side, **UUID v4** is the right default. If you need time-sortable IDs for time-series workloads, consider ULID.

Try our [UUID Generator](/tools/uuid-generator) to generate RFC 4122 compliant UUIDs — v1, v4, and v5 — directly in your browser.

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