Cached data detection

One or more computer storage media having stored thereon multiple instructions implementing a program that, when executed by one or more processors of a computing device, cause the one or more processors to:

• receive, from a remote service in response to a page request, a page and a session identifier associated with a usage session of the program;
• send a cached data detection request targeting the remote service;
• receive a response to the cached data detection request;
• determine, based on whether a particular indication is received with the response, whether the cached data detection response is provided by the remote service or by a local cache of the computing device;
• and
• determine that data for the remote service is in the local cache if the cached data detection response is provided by the local cache, otherwise determine that data for the remote service is not in the local cache if the cached data detection response is provided by the remote service.

A method implemented in a service, the method comprising:

• receiving, from programs running on computing devices, page requests for one or more pages from the service;
• storing, for each page request, information regarding the page request and a session identifier associated with a usage session of the program from which the page request is received;
• receiving, from one or more of the programs, both a cached data detection request and the session identifier associated with the usage session of the program from which the cached data detection request is received, the cached data detection request comprising a request for a particular file identified by a uniform resource locator (URL);
• storing, for each cached data detection request, information regarding the cached data detection request and the session identifier;
• and
• returning, in response to each cached data detection request, a response with both the particular file and a cookie indicating that the response with the particular file is being returned by the service, the particular file having a same cache retention policy as other files provided to the program from the service.