# isUuid4

Tests whether a string is an RFC UUID version 4 value.

## Signatures

```ts
export declare const isUuid4: (value: string) => value is Uuid4;
```

## Why

Runtime refinement restores trust after serialization has erased the TypeScript brand.

## Ownership and lifetime

This pure predicate acquires no resources and retains no input.

## Examples

```ts
import { isUuid4 } from "@typed/id/Uuid4"
isUuid4("550e8400-e29b-41d4-a716-446655440000")
```