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GTMetrix and Google Lighthouse: Site Speed Update [2020]


Here in the office GTMetrix is a tool we use nearly every day for testing site speed. That could be a quick check after making web changes or as part of a number of tools for working on actively improving site speed. GTMetrix is one of our go to tools!

Recently, the team at GTMetrix have announced they are about to undergo a major upgrade.

Alongside the inclusion of some paid-for plans, this site speed update includes a move away from Google PageSpeed and YSlow libraries and towards the newer Google Lighthouse Metrics.

No Longer Chasing A Grade

We have written about site speed in a previous article title ‘How to Improve your Site Speed in 2020: A Beginner’s Guide.’ As we mentioned there, tools like GTMetrix and others often test your page and give you a speed grade.

It’s easy to understand and who doesn’t like getting an A!

However, these grades are based on the older PageSpeed and YSlow metrics. They are focused more on the actual structure of the site than its real-life speed.

You could effectively get an A whilst having a load time of 16.5 as shown in GTMetrix’s own example!

site speed




Credit: GTMetrix.com

You need to look at both the grades and the numbers next to them. However, we know it’s hard not to get distracted and focus on only half of the picture!

What is Google Lighthouse and what has changed with the new Core Web Vitals?

Lighthouse is an open source tool release by Google in 2016 and is the replacement standard in performance testing.

It has a lot stronger focus on user experience which should always be the primary focus of any site speed work. Instead of focusing on just the structural elements of the site, Lighthouse focuses on how fast the page is from a user’s perspective.

Alongside these changes GTMetrix will also feature the new ‘Core Web Vitals.’  These are Googles new metrics relating to site speed and indications are that they will likely be a ranking factor moving forward.

Core Web Vitals are an updated set of metrics relating to user experience made up of three specific measure:

  • Largest Contentful Paint (LCP) – This is how long it takes a page to load from a user perspective. Kept simply, its the time it takes from clicking on a link to the visitor being able to engage with the first part of the page. One thing to note is that ‘Good’ results are 2 seconds and under’ which is currently a lot lower than the average site speed. This shows how much Google is focusing on further improvements to site speed.
  • First Input Delay (FIP) – This takes LCP a step further. It measures how long from the first click to the website being ready to accept clicks such as selecting a menu or filling in a form. This is a definite shift in focus from just loading times to how long before a page becomes usable.
  • Cumulative Layout Shift (CLS) – Instead of being related to times as with the previous two metrics, CLS relates to how stable the page is as it loads. When the page loads, does the content shift around as images and videos start to load or does it stay relatively static? The more the page shifts around the longer before a user actually knows where they should be looking. This leads to a poor user experience.

What does the site speed update mean and how to prepare for them

GTMetrix shifting to using Lighthouse and Core Web Vitals is a key sign in showing their increasing importance. This site speed update is something that web developers should definitely be taking into account.

A move towards better user experience is always a good thing. However, it may come as a surprise to many when previously ‘fast’ sites suddenly start coming up with bad test results.

We are also seeing that a lot of the common speed plugins such as WPRocket are making large changes. They are adding a lot of new features to further improve site speed. They’re taking into account the new metrics, so it’s important to keep these up to date and test the new functionality.

Also, as long as you are following best practices and not just following a nice speed grade that you will already be a step ahead when it comes to the new metrics.

User experience is essential for so many reasons and this is only re-enforced with the new changes.

There are so many factors to site speed and we have tried to cover the most important changes in this article. As with everything, we would be more than happy to talk through these in more details so drop us an email on enquiries@drumbeatmarketing.co.uk

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