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# lib.footer

- **Type:**

```ts
type Footer = {
  js?: string;
  css?: string;
  dts?: string;
};
```

- **Default:** `{}`
- **Top-level config:** Supported

Inject content into the bottom of each JavaScript, CSS or declaration file.

## Object type

### footer.js

- **Type:** `string`
- **Default:** `undefined`

Inject content into the bottom of each JavaScript output file.

### footer.css

- **Type:** `string`
- **Default:** `undefined`

Inject content into the bottom of each CSS output file.

### footer.dts

- **Type:** `string`
- **Default:** `undefined`

Inject content into the bottom of each declaration output file.

## Notice

The footer content in JavaScript and CSS file is based on the [BannerPlugin](https://rspack.rs/plugins/webpack/banner-plugin) of Rspack. You should notice the following points:

- `raw: true` is enabled by default, so the footer content will be injected as a raw string instead of wrapping in a comment. So if you want to inject a comment, you should add `/*` and `*/` or other comment syntax by yourself.
- The `stage` option is set to the stage after the JavaScript and CSS files are optimized, thus preventing the footer content from being optimized away.

## Customize footer content

If the above default settings cannot meet your requirements, you can customize the footer content through `tools.rspack.plugins` to add a [BannerPlugin](https://rspack.rs/plugins/webpack/banner-plugin) instance with the corresponding options.

```ts title="rslib.config.ts"
export default {
  lib: [
    {
      // ...
      tools: {
        rspack: {
          plugins: [
            new rspack.BannerPlugin({
              footer: true,
              // ... options
            }),
          ],
        },
      },
    },
  ],
};
```

:::warning

The footer content in declaration files is handled differently from JavaScript and CSS files. It is written directly using the file system API, so setting `BannerPlugin` will not affect it.

:::