*__Note:__ The XHR is a deprecated web feature and applications should be using the new [Fetch API] which does not have
the same issues regarding redirects (the [Fetch API] allows developers to
[control how to handle them](https://developer.mozilla.org/en-US/docs/Web/API/Request/redirect)). As such the fact
a proxy does not support it should only be seen as a means to communicate a feature not that the proxy should not be
used.*
XML HTTP Requests do not typically redirect browsers when returned 30x status codes. Instead, the standard method is to
return a 401 status code with a Location header. While this may seem trivial; currently there isn't wide support for it.
For example the nginx ngx_http_auth_request_module does not seem to support this in any way.
### Request Method
Authelia detects the upstream request method using the X-Forwarded-Method header. Some proxies set this out of the box,
some require you to configure this manually. At the present time all proxies that have
[Standard Support](#standard-support) do support this.
## Specific proxy notes
### HAProxy
[HAProxy] is only supported via a lua [module](https://github.com/haproxytech/haproxy-lua-http). Lua is typically not
available in [Kubernetes]. You would likely have to build your own [HAProxy] image.
### Envoy
[Envoy] is currently not documented however we believe it is likely to be technically supported. This should be possible
via [Envoy]'s [external authorization](https://www.envoyproxy.io/docs/envoy/latest/api-v3/extensions/filters/http/ext_authz/v3/ext_authz.proto.html#extensions-filters-http-ext-authz-v3-extauthz).
### Caddy
[Caddy] needs to be version 2.5.1 or greater.
### Apache
[Apache] is not supported as it has no module that supports this kind of authentication method. It's not certain this
would even be possible, however if anyone did something like this in the future we'd be interested in a contribution.
### IIS
Microsoft [IIS] is not supported as it has no module that supports this kind of authentication method. It's not certain
this would even be possible, however if anyone did something like this in the future we'd be interested in a
