# methodNotAllowed

**Kind:** Function

**Source:** [`src/middleware/method-not-allowed/index.ts`](https://github.com/honojs/hono/blob/main/src/middleware/method-not-allowed/index.ts#L59)

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

Method Not Allowed Middleware for Hono.

Returns a `405 Method Not Allowed` response with an `Allow` header when the request path
matches a registered route but the request method is not supported.

`methodNotAllowed` creates Hono middleware that returns a Method Not Allowed response when a request matches a registered path but uses an unsupported HTTP method. It adds an `Allow` header containing the methods registered for that path.

## Signature

```ts
function methodNotAllowed(options: MethodNotAllowedOptions<E>): MiddlewareHandler<E>
```

## Parameters

| Name | Type |
|---|---|
| `options` | `MethodNotAllowedOptions<E>` |

**Returns:** `MiddlewareHandler<E>`

## Diagram

```mermaid
graph LR
  Request --> Router
  Router -->|Path and method match| RouteHandler
  Router -->|Path matches, method does not| MethodNotAllowed
  MethodNotAllowed --> AllowHeader
  AllowHeader --> Response
```

## Usage

```ts
import { Hono } from 'hono'
import { methodNotAllowed } from 'hono/method-not-allowed'

const app = new Hono()

app.use(methodNotAllowed())

app.post('/entries', (c) => {
  return c.json({ created: true })
})

export default app
```

## AI Coding Instructions

- Register `methodNotAllowed()` before route definitions so it can inspect routing results after downstream handlers run.
- Keep route methods explicit with `app.get`, `app.post`, and related route APIs so the middleware can produce the correct `Allow` header.
- Do not replace the Method Not Allowed response or remove its `Allow` header in later middleware.
- Use this middleware for applications that need to distinguish an unknown path from a known path with an unsupported method.