---
url: >-
  https://adk.nht.io/api/@nhtio/adk/batteries/media/functions/replaceExtension.md
---

# Function: replaceExtension()

```ts
function replaceExtension(filename: string, ext: string): string;
```

Defined in: [src/batteries/media/formats.ts:174](https://github.com/NHTIO/ADK/blob/v1.20260713.1/src/src/batteries/media/formats.ts#L174)

Replace (or add) a filename's extension.

## Parameters

| Parameter  | Type     | Description                         |
| ---------- | -------- | ----------------------------------- |
| `filename` | `string` | The original filename.              |
| `ext`      | `string` | The new extension, without the dot. |

## Returns

`string`

The filename with the new extension.