Hi Francis,
thank you for your fast reply.

I took a look at the header nginx response.

##### Header nginx
### Response Header
## Chrome
HTTP/1.1 200 OK
Server: nginx
Date: Wed, 19 Oct 2016 09:54:07 GMT
Content-Type: text/html;charset=UTF-8
Content-Length: 15991
Connection: keep-alive
Content-Language: de-DE
Vary: Accept-Encoding
Content-Encoding: gzip
X-Cache-Status: MISS

## Firefox
HTTP/1.1 200 OK
Server: nginx
Date: Wed, 19 Oct 2016 09:53:50 GMT
Content-Type: text/html;charset=UTF-8
Transfer-Encoding: chunked
Connection: keep-alive
Content-Language: de-DE
Vary: Accept-Encoding
Content-Encoding: gzip
X-Cache-Status: MISS


How can i have a look for the headers of upstream servers?

For testing i had set "proxy_ignore_headers" to "X-Accel-Expires Expires Cache-Control Vary Set-Cookie X-Accel-Limit-Rate X-Accel-Buffering X-Accel-Charset" but there is no difference.

best,
Carsten