File Proxy Client proxies any file from your server Google Tag Manager subdomain.

Priority - determines the order in which clients will run. Higher numbers run first, and the first client that matches the incoming request will become the active client for that request.

File URL - specify the URL where content/file is located. 

Accepted File Path - path for file serving.

Response Content-Type - Content-type header value.

Cache file between requests - when enabled, use template cache for file serving—more info about this.

Request Settings:

• Request Timeout - specify request timeout. 
• Request Headers - add values and names of the response headers

Response Settings:

• Custom HTTP Response Code
• Response Headers - add values and names of the response headers.