Software Architect's Handbook

Server push

HTTP/2 provides a feature in which the server can push responses that it thinks a client will need. When a resource is requested from a client, it may contain references to other resources that are needed. Rather than wait for the client to send additional requests for these required resources, the server already knows what resources will be needed and can proactively send them.

This feature is similar to inlining a resource, which is a technique that is sometimes used to improve performance by reducing the number of requests necessary. Inlining is accomplished by embedding a resource, such as JavaScript, CSS, or images, into an HTML page. With server push, there is no longer a need to inline resources. We get the same advantages ...