traefik/docs/content/middlewares/http/contenttype.md

# ContentType

Handling Content-Type auto-detection
{: .subtitle }

The Content-Type middleware - or rather its `autoDetect` option -
specifies whether to let the `Content-Type` header,
if it has not been defined by the backend,
be automatically set to a value derived from the contents of the response.

As a proxy, the default behavior should be to leave the header alone,
regardless of what the backend did with it.
However, the historic default was to always auto-detect and set the header if it was not already defined,
and altering this behavior would be a breaking change which would impact many users.

This middleware exists to enable the correct behavior until at least the default one can be changed in a future version.

!!! info

    As explained above, for compatibility reasons the default behavior on a router (without this middleware),
    is still to automatically set the `Content-Type` header.
    Therefore, given the default value of the `autoDetect` option (false),
    simply enabling this middleware for a router switches the router's behavior.

    The scope of the Content-Type middleware is the MIME type detection done by the core of Traefik (the server part).
    Therefore, it has no effect against any other `Content-Type` header modifications (e.g.: in another middleware such as compress).

## Configuration Examples

```yaml tab="Docker"
# Disable auto-detection
labels:
  - "traefik.http.middlewares.autodetect.contenttype.autodetect=false"
```

```yaml tab="Kubernetes"
# Disable auto-detection
apiVersion: traefik.containo.us/v1alpha1
kind: Middleware
metadata:
  name: autodetect
spec:
  contentType:
    autoDetect: false
```

```yaml tab="Consul Catalog"
# Disable auto-detection
- "traefik.http.middlewares.autodetect.contenttype.autodetect=false"
```

```json tab="Marathon"
"labels": {
  "traefik.http.middlewares.autodetect.contenttype.autodetect": "false"
}
```

```yaml tab="Rancher"
# Disable auto-detection
labels:
  - "traefik.http.middlewares.autodetect.contenttype.autodetect=false"
```

```yaml tab="File (YAML)"
# Disable auto-detection
http:
  middlewares:
    autodetect:
      contentType:
        autoDetect: false
```

```toml tab="File (TOML)"
# Disable auto-detection
[http.middlewares]
  [http.middlewares.autodetect.contentType]
     autoDetect=false
```

## Configuration Options

### `autoDetect`

`autoDetect` specifies whether to let the `Content-Type` header,
if it has not been set by the backend,
be automatically set to a value derived from the contents of the response.