Learning HTTP/2

Preface

HTTP/2, also called h2 for simplicity, is a major revision of the HTTP network protocol used by the World Wide Web, meant to improve the perceived performance of loading web content.

Since HTTP/1.1 (h1) was approved in 1999, the web has changed significantly from mostly text-based web pages that weighed a few kilobytes and included less than 10 objects, to today’s media-rich websites that weigh on average over 2 megabytes,¹ and include an average of 140 objects. However, the HTTP protocol used to deliver the web content did not change in the intervening years, making room for a new industry of Web Performance experts who specialize in coming up with workarounds to help the aging protocol load web pages faster. People’s expectations for performance have changed too—while in the late ’90s people were willing to wait up to seven seconds for a page to load, a 2009 study by Forrester Research found that online shoppers expected pages to load under two seconds, with a large share of users abandoning sites where pages take over three seconds to load. A recent study by Google showed that a even a delay of 400 milliseconds (the blink of an eye) will cause people to search less.

That’s why h2 was created—a protocol that can better handle today’s complex pages without sacrificing speed. HTTP/2’s adoption has been increasing² as more website administrators realize they can improve the perceived performance of their websites with little effort.

We all use h2 every day—it powers some ...