I have a server endpoint that supports both HTTP/1.1 and HTTP2. For testing purposes, I want to try downloading content from the endpoint with both HTTP/1.1 and HTTP2 connections, possibly at the same time.

When I request data from the endpoint with an XMLHttpRequest, it automatically uses HTTP2, without me including the Connection: Upgrade header.

Is there a way to force an XMLHttpRequest to use HTTP/1.1 for the underlying TCP connection? What about other protocols, such as Quic or SPDY?

解决方案

No.

From Remy Lebeau's comment:

The browser decides which protocol it wants to use as an implementation detail of the XmlHttpRequest object. You can't force a particular choice from inside your script.