An action response of any type (HTML or JSON, for example) may be cached in the client in order to improve performance. Needless to say, this should only happen if the result that it is returning rarely changes. This is specified in RFC 7234, HTTP/1.1 Caching (https://tools.ietf.org/html/rfc7234).
Essentially, response caching is a mechanism by which the server notifies the client (the browser or a client API) to keep the response returned (including headers) for a URL for a certain amount of time and to use it, during that time, for all subsequent invocations of the URL. Only the GET HTTP verb can be cached, as it is designed to be idempotent: PUT, POST, PATCH, or DELETE cannot be cached.
We add support for resource caching in ConfigureServices as follows:
services.AddResponseCaching();
We use it in Configure, which basically adds the response caching middleware to the ASP.NET Core pipeline:
app.UseResponseCaching();...
