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What is HTTP/2 And Why Should You Care?

If you’re involved in SEO, you’ll know how complex and multi-faceted a process it can be. There is no end to the different things you have to know about. From AMP to Zebra algorithm updates, you have to be across it all. That can make it tempting to let some things pass you by. Especially if their importance to SEO isn’t immediately obvious. It’s for that reason that you might not have given HTTP/2 much thought.

We’re going to explain why that might be a major mistake. This quick (and mercifully non-technical) introduction to HTTP/2 is pitched specifically with SEO in mind. It will give you the basics on what HTTP/2 is and why it matters to SEO and therefore to you. Here’s what our beginner’s guide to HTTP/2 will include:


  • A quick refresher on latency
  • A rundown of the current network connection status quo
  • A simple description and explanation of HTTP/2
  • All the reasons why you need to care about HTTP/2

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A Quick Refresher on Latency

Before we really crack on with HTTP/2, it’s worth quickly talking about latency. In web terms, latency is the time it takes for a network connection to open across a distance. On the most basic level, that means the time it takes for information to get from your computer to the server and back.


Source: https://www.keycdn.com/support/what-is-latency


Latency is one of the main issues affecting the speed of the web. It and bandwidth combine to determine the speed at which pages load. Where latency is the time it takes for information to open across a distance, bandwidth is basically how much information can be opened at a time.

HTTP/2 was developed by Google as a new kind of network connection. Its main aim was to reduce latency and therefore speed up the web. We’ll get to the nitty gritty of HTTP/2 later. First let’s look at the current status quo that HTTP/2 was developed to replaced.


The Current Situation

Requests for web pages and resources are communicated in HTTP. It’s basically the language your browser speaks to the server. The current standard version of HTTP is HTTP 1.1. It has been the standard for around 20 years. The only change in that time has been the introduction of HTTPS.



An HTTP 1.1 request involves information being passed from your browser to the server. The server will then send back a response to that request. Both the request and response can travel at the speed of light but no faster. The transfer of information is not instantaneous.

It’s because of that, that latency is an issue. It’s also why the distance between your browser and the server makes a difference to web speed. As each individual request and response is small, it’s tempting to assume that the difference is slight.

That’s not wholly accurate. That’s because a typical website comprises a sequence of requests and responses, not just one. An HTML file may reference images in different formats and JavaScript files, for instance. Even the simplest website often involves between 50 and 100 requests and responses.

The time taken for those requests and responses can build up. HTTP 1.1 connections only allow for one request or one response to be transferred at a time. The multiple requests required for a webpage occur consecutively rather than concurrently.


Source: https://www.incapsula.com/cdn-guide/glossary/http2.html


To account for this, browsers will often open around six HTTP 1.1 connections at a time. Each new one takes the time of one ‘round trip’ from the browser to the server to open. That’s one trip before the connection can be used to carry any information.

Even six HTTP 1.1 connections aren’t sufficient for 50-100 requests and responses to be completed at the same time. With HTTP 1.1, some requests and responses must queue up and wait for a free connection. This is called ‘head of line blocking’. It is a major reason why HTTP 1.1 connections suffer higher latency and are slower.

HTTPS works in the same way as HTTP 1.1. The only difference is that it’s a secure connection. That means people are blocked from seeing the information contained in requests and responses. That’s important for security but does nothing to help with latency. That’s where HTTP/2 comes in.


What is HTTP/2?

HTTP/2 is a new kind of network connection to replace HTTP 1.1. It was first born out of a Google development called SPDY (speedy). The main idea behind both SPDY and HTTP/2 is to provide a solution to the HTTP 1.1 issues with latency. To speed up network connections and the web in general.

There are lots of features and elements to HTTP/2 which help do just that. To avoid having to get too technical, we’re going to focus on just the two main ones. They are:


  • Multiplexing
  • Server Push



Multiplexing is the main HTTP/2 feature that solves the problem of head of line blocking. It means that a single HTTP/2 connection can carry more than one request or response at a time. You don’t have to wait for new connections to be built. Requests and responses also don’t have to queue until a free connection becomes available.


source: https://www.advancedwebranking.com/blog


One single HTTP/2 connection can handle the many requests and responses associated with a website far more quickly. That’s without altering the information contained in those requests and responses. All of that stays the same. This is crucial when it comes to implementing HTTP/2. To do so, you don’t have to change web platform or CMS. You also won’t need to write any new code.


Server Push

Server push is another key feature of HTTP/2. It allows a server to pre-empt required responses when it receives a request. By doing so, it can then respond to one request with multiple responses. Thus taking advantage of the multiplexing capability afforded by HTTP/2.


source: https://www.smashingmagazine.com


Take, for example, a situation where a server receives a request for an HTML file. The server may know from previous requests that the file also requires a CSS and a JavaScript file. Thanks to server push, it can ‘push’ those resources into your browser’s cache. It won’t have to receive the separate requests for them.

The potential benefit of this is obvious. It means that your browser will get the responses required without having to complete as many request/response cycles. As HTTP/2 is new(ish), however, server push isn’t always implemented perfectly. You can often have resources pushed to a browser’s cache that it doesn’t need. It may already have them cached from previous requests.


Why Should You Care?

You’re probably wondering right now why an SEO agency in Bristol cares about HTTP/2. More to the point, you’re likely wondering why you should care. There are plenty of compelling reasons. In short, HTTP/2 matters to you because it matters to Google and to SEO.

As we’ve discussed at length, HTTP/2 has much lower latency than HTTP 1.1 or HTTPS. It is a faster connection as a result and has a big impact on page load time and site speed.


Source: https://www.igvita.com/2012/07/19/latency-the-new-web-performance-bottleneck/


The graph on the left shows the impact increased bandwidth can have on page load time. If somewhere between 3 Mbps and 10 Mbps of bandwidth is available, page load time changes little. The graph on the right plots latency against page load time. It shows that decreasing latency has a marked and continual effect.

The data that created the graph came from a study by Google’s Ilya Grigorik. According to the graph, a page can load around four times faster if latency delivers a round trip time (RTT) of 20ms rather than 240ms. That’s a significant difference and is what’s important to SEO.

Site speed is an SEO ranking factor. That means that Google’s algorithms care how quickly pages and sites load. They measure it and take it into account when ranking them. Pages and domains with low page load times and high site speed will be looked upon more favourably. That means adopting HTTP/2 could indirectly but significantly improve your SERP rankings.

That’s not the end of the story. Google are also very interested in user experience. They want sites to be as helpful and as user-friendly as possible. They also want the utility of sites to be consistent across all devices. HTTP/2 is applicable to PCs and mobile devices alike. Its impact on latency and thus site speed could deliver exactly what Google are looking for.

What shouldn’t be overlooked at this point either, is how easy it actually is to implement HTTP/2. If your site is already secure and uses HTTPS, you may have to do very little to switch to HTTP/2. In fact, it may be possible simply by updating your server software. When making other SEO improvements can be really costly, this easy and cheap change is well worth doing.

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