# FastifyStaticOptions

**Kind:** Interface

**Source:** [`packages/platform-fastify/interfaces/external/fastify-static-options.interface.ts`](https://github.com/nestjs/nest/blob/master/packages/platform-fastify/interfaces/external/fastify-static-options.interface.ts#L73)

**Part of:** [Platform Fastify](subsystem-packages-platform-fastify)

`FastifyStaticOptions` configures static asset serving for the Fastify platform adapter. It controls the asset root directory, URL prefix, reply decoration, caching headers, redirects, directory listings, and wildcard route behavior when registering static-file support.

## Properties

| Property | Type |
|---|---|
| `root` | `string | string[] | URL | URL[]` |
| `prefix` | `string` |
| `prefixAvoidTrailingSlash` | `boolean` |
| `serve` | `boolean` |
| `decorateReply` | `boolean` |
| `schemaHide` | `boolean` |
| `setHeaders` | `(res: SetHeadersResponse, path: string, stat: Stats) => void` |
| `redirect` | `boolean` |
| `wildcard` | `boolean` |
| `list` | `boolean | ListOptionsJsonFormat | ListOptionsHtmlFormat` |
| `allowedPath` | `( pathName: string, root: string, request: FastifyRequest, ) => boolean` |
| `preCompressed` | `boolean` |
| `acceptRanges` | `boolean` |
| `cacheControl` | `boolean` |
| `dotfiles` | `'allow' | 'deny' | 'ignore'` |
| `etag` | `boolean` |
| `extensions` | `string[]` |
| `immutable` | `boolean` |
| `index` | `string[] | string | false` |
| `lastModified` | `boolean` |
| `maxAge` | `string | number` |
| `constraints` | `RouteOptions['constraints']` |

## Diagram

```mermaid
graph LR
  A[FastifyStaticOptions] --> B[root]
  A --> C[prefix]
  A --> D[Serving behavior]
  A --> E[Response behavior]
  A --> F[Directory listing]

  D --> D1[serve]
  D --> D2[redirect]
  D --> D3[wildcard]

  E --> E1[decorateReply]
  E --> E2[schemaHide]
  E --> E3[setHeaders]

  F --> F1[list]
```

## Usage

```ts
import { join } from 'node:path';
import type { FastifyStaticOptions } from './interfaces/external/fastify-static-options.interface';

const staticOptions: FastifyStaticOptions = {
  root: join(process.cwd(), 'public'),
  prefix: '/assets/',
  prefixAvoidTrailingSlash: false,
  serve: true,
  decorateReply: true,
  schemaHide: true,
  redirect: true,
  wildcard: true,
  list: false,
  setHeaders(res, path, stat) {
    if (path.endsWith('.js') || path.endsWith('.css')) {
      res.setHeader('Cache-Control', 'public, max-age=31536000, immutable');
    }

    res.setHeader('Content-Length', stat.size);
  },
};

// Example: pass staticOptions when configuring Fastify static serving.
```

## AI Coding Instructions

- Use an absolute filesystem path for `root`; provide an array of roots only when serving assets from multiple locations.
- Keep `prefix` aligned with application routing conventions, including whether a trailing slash is expected.
- Use `setHeaders` for cache and content-related headers; avoid performing asynchronous work in this callback.
- Disable `decorateReply` only if application code does not need Fastify reply helpers for static files.
- Enable `list` only for controlled or development environments, as directory listings can expose file names and structure.