Overview#Fetch API provides an interface for fetching resources (including across the network) and is a WHATWG Standard.
Fetch API provides a generic definition of Request and Response objects (and other things involved with network requests). This will allow them to be used wherever they are needed in the future, whether it’s for Service Workers, Cache API and other similar things that handle or modify requests and responses, or any kind of Use case that might require you to generate your own responses programmatically.
Fetch API also provides a definition for related concepts such as Cross Origin Resource Sharing (CORS) and the HTTP Header Field Origin header semantics, supplanting their separate definitions elsewhere. (RFC 6454)