# AdditionalHeaders

**Kind:** Type

**Source:** [`packages/core/router/sse-stream.ts`](https://github.com/nestjs/nest/blob/master/packages/core/router/sse-stream.ts#L38)

**Part of:** [Core](subsystem-packages-core)

## Definition

```ts
Record< string, string[] | string | number | undefined >
```

## Relationships

- IMPORTS → `MessageEvent`
- IMPORTS → `isNil`
- IMPORTS → `isObject`
- IMPORTS → `isUndefined`