HTTP1 vs HTTP2 - jellyfish-tom/TIL GitHub Wiki

[SOURCES]

• https://www.cloudflare.com/learning/performance/http2-vs-http1.1/
• https://cheapsslsecurity.com/p/http2-vs-http1/

Overview

HTTP stands for hypertext transfer protocol, and it is the basis for almost all web applications. More specifically, HTTP is the method computers and servers use to request and send information. For instance, when someone navigates to cloudflare.com on their laptop, their web browser sends an HTTP request to the Cloudflare servers for the content that appears on the page. Then, Cloudflare servers send HTTP responses with the text, images, and formatting that the browser displays to the user.

Generally speaking HTTP/2 is much faster and more efficient than HTTP/1.1. One of the ways in which HTTP/2 is faster is in how it prioritizes content during the loading process.

What is prioritization?

In the context of web performance, prioritization refers to the order in which pieces of content are loaded. Prioritization affects a webpage's load time.

HTTP/2 offers a feature called weighted prioritization. This allows developers to decide which page resources will load first, every time. In HTTP/2, when a client makes a request for a webpage, the server sends several streams of data to the client at once, instead of sending one thing after another. This method of data delivery is known as multiplexing. Developers can assign each of these data streams a different weighted value, and the value tells the client which data stream to render first.

What are the other differences between HTTP/2 and HTTP/1.1 that impact performance?

Multiplexing

HTTP/1.1 loads resources one after the other, so if one resource cannot be loaded, it blocks all the other resources behind it. In contrast, HTTP/2 is able to use a single TCP connection to send multiple streams of data at once so that no one resource blocks any other resource. HTTP/2 does this by splitting data into binary-code messages and numbering these messages so that the client knows which stream each binary message belongs to.

Server push

Typically, a server only serves content to a client device if the client asks for it. However, this approach is not always practical for modern webpages, which often involve several dozen separate resources that the client must request. HTTP/2 solves this problem by allowing a server to "push" content to a client before the client asks for it. The server also sends a message letting the client know what pushed content to expect – like if Bob had sent Alice a Table of Contents of his novel before sending the whole thing.

Header compression

Small files load more quickly than large ones. To speed up web performance, both HTTP/1.1 and HTTP/2 compress HTTP messages to make them smaller. However, HTTP/2 uses a more advanced compression method called HPACK that eliminates redundant information in HTTP header packets. This eliminates a few bytes from every HTTP packet. Given the volume of HTTP packets involved in loading even a single webpage, those bytes add up quickly, resulting in faster loading.

What is HTTP/3?

HTTP/3 is the next proposed version of the HTTP protocol. HTTP/3 does not have wide adoption on the web yet, but it is growing in usage. The key difference between HTTP/3 and previous versions of the protocol is that HTTP/3 runs over QUIC instead of TCP. QUIC is a faster and more secure transport layer protocol that is designed for the needs of the modern Internet.

How to Implement HTTP/2 on Your Website

Since using HTTP/2 is an invisible process when correctly implemented, your website may already be using it without your realization. There is an easy way to check this:

Open the web developer tool on the web browser (like Firefox). Under the network tab, select any of the resources and check the version number under the headers tab. While HTTP/2 does not mandate the use of SSL, it is crucial to install an SSL certificate because the leading browsers, including Firefox and Chrome, have decided to implement HTTP/2 only over TLS (HTTPS). In order to enable HTTP/2 it is essential to get an SSL/TLS certificate and make every page on the website https.

At the web server level, it could be as simple as a software update, for example, Apache began support for HTTP/2 in version 2.4.17.