ContentType

Handling Content-Type auto-detection

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

Docker

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

Kubernetes

# Disable auto-detection
apiVersion: traefik.containo.us/v1alpha1
kind: Middleware
metadata:
  name: autodetect
spec:
  contentType:
    autoDetect: false

Consul Catalog

# Disable auto-detection
- "traefik.http.middlewares.autodetect.contenttype.autodetect=false"

Marathon

"labels": {
  "traefik.http.middlewares.autodetect.contenttype.autodetect": "false"
}

Rancher

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

File (YAML)

# Disable auto-detection
http:
  middlewares:
    autodetect:
      contentType:
        autoDetect: false

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.