# appendTrailingSlash

**Kind:** Function

**Source:** [`src/middleware/trailing-slash/index.ts`](https://github.com/honojs/hono/blob/main/src/middleware/trailing-slash/index.ts#L128)

**Part of:** [Middleware](subsystem-src-middleware)

Append trailing slash middleware for Hono.
Append a trailing slash to the URL if it doesn't have one. For example, `/path/to/page` will be redirected to `/path/to/page/`.

`appendTrailingSlash` creates Hono middleware that redirects requests whose path does not end with `/`. It runs before route handling so canonical slash-terminated URLs reach the matching route.

## Signature

```ts
function appendTrailingSlash(options: AppendTrailingSlashOptions): MiddlewareHandler
```

## Parameters

| Name | Type |
|---|---|
| `options` | `AppendTrailingSlashOptions` |

**Returns:** `MiddlewareHandler`

## Diagram

```mermaid
graph LR
  Request[Incoming request] --> Middleware[appendTrailingSlash middleware]
  Middleware --> Check{Path ends with slash?}
  Check -- No --> Redirect[Redirect to path with slash]
  Check -- Yes --> Next[Continue to next middleware or route]
```

## Usage

```ts
import { Hono } from 'hono'
import { appendTrailingSlash } from 'hono/trailing-slash'

const app = new Hono()

app.use(appendTrailingSlash())

app.get('/docs/', (c) => {
  return c.text('Documentation')
})

export default app
```

## AI Coding Instructions

- Register `appendTrailingSlash()` before routes that expect slash-terminated paths.
- Apply the middleware at the app level when all routes should use trailing slashes, or mount it on a route prefix for narrower behavior.
- Do not add separate redirect logic inside route handlers when this middleware already handles path normalization.
- Test requests with and without a trailing slash, including paths that include query parameters.