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Page Speed Scores in 2021

Page Speed Scores in 2021

Page Speed Scores in 2021

Many of our clients are on WordPress. For these clients, optimizing page speed scores used to be a slam dunk. We know the tricks and we rarely had problems getting our clients A’s and B’s.

In November of 2020, GTMetrix announced a new system for scoring. Suddenly, scores were all over the place.

From GTMetrix:

GTmetrix has undergone its biggest change yet, replacing the PageSpeed/YSlow libraries with Lighthouse, the industry standard in web performance.

With GTmetrix now being powered by Lighthouse, the new GTmetrix Report has been redesigned extensively to incorporate the Lighthouse data and metrics.

A new scoring system has been implemented, creating an all-new GTmetrix Grade, alongside new Performance and Structure Scores. The new GTmetrix Report also sees the addition of new tabs, visualizations, graphs, and deeper insights.

The scoring system used in the new GTmetrix Report is loosely based on the Lighthouse scoring system. However, it has been augmented by our own expertise and proprietary formulas to deliver the unique GTmetrix flavor that users have come to love and trust over the years.

The resultant product is the new GTmetrix Grade – a weighted grade derived from the new Performance and Structure Scores, which replace the old PageSpeed and YSlow Scores (Legacy Reports).


If you’re not checking page speed score frequently, you might not have noticed the change in the reporting options but you most assuredly noticed that your page scores were either quite a bit better, or quite worse.

This was the case for us and for some of our clients.


The GTmetrix Grade is a weighted average of the two new percentage-based scores, namely:


  • The Performance Score (70%)
  • The Structure Score (30%)

The GTmetrix Grade is based on a simple formula, which currently assigns a 70/30 weighting for the Performance and Structure Scores respectively.


The Performance Score tells you how well your page performs from a user perspective.

This score is made up of 6 key metrics with the following weights:

Each metric is measured and calculated as a score, then compared to a threshold, and the aggregate result (with the appropriate weighting) makes up the final Performance Score.

Complete details of your Performance Score are listed in the Performance Tab of the GTmetrix Report.


How does this compare to the Performance score I see on Google PageSpeed Insights or web.dev?

While the official Google tools are also driven by Lighthouse, they use their own hardware and testing methodologies to generate the Performance score.

Here are a few key differences that would make the scores vary:

  • Geographic differences
    It’s unknown if Google does tests in servers based on their geographic region. GTmetrix allows you to define which test region to analyze your page from.
  • Hardware differences
    GTmetrix and Google will likely have different CPU/Memory designations for tests, which will affect the metrics.
  • Network differences
    Differences in network connections and variances may contribute to changes in individual metrics.
  • Other Google-magic
    Google may have additional considerations when calculating the Performance score (e.g., Lantern for CPU/Network throttling).

Other Tools

Page Speed Insights from Google is another tool. It’s been a standard for as long as I can remember, but it doesn’t provide the easy-to-digest dashboard like GTMetrix does. Still, it’s an unbiased grading report and therefore, should be reviewed.


The newest one is Google’s new browser, Canary.

Chrome Canary is Google’s cutting edge web browser that is mainly targeted at developers, seasoned techies, and browser enthusiasts. Chrome browser has four versions. Namely, they are Stable, Beta, Dev, and Canary. Both Dev and Canary versions are intended for developers. The Canary version gets updates every night, and the Dev version gets updates every week.

With Canary, we can monitor the ONLY three metrics that matter to Google for page speed score ratings:

Largest Contentful Paint – Largest Contentful Paint is the metric that measures the time a website takes to show the user the largest content on the screen, complete and ready for interaction. Google defines that this metric considers only the content above the page’s fold, meaning everything that appears without scrolling

First Input Delay – First Input Delay (FID) measures the time from when a user first interacts with your site (i.e. when they click a link, tap on a button, or use a custom, JavaScript-powered control) to the time when the browser is actually able to respond to that interaction.

Cumulative Layout Shift – Cumulative Layout Shift (CLS) is a Core Web Vitals metric calculated by summing all layout shifts that aren’t caused by user interaction. CLS looks at the proportion of the viewport that was impacted by layout shifts, and the movement distance of the elements that were moved.

CLS is becoming a ranking factor in May 2021 when Google’s Page Experience Update rolls out. That means your CLS score will affect your SEO. While it’s likely to be a very minor factor, your CLS score (along with the other Web Vitals) may reflect on the traffic you get from Google and other search engines.

Essentially, these are together called “Core Web Vitals.”

This client’s site was showing us poor GTMetrix scores despite aggressive speed optimization efforts. The Canary scores were better, but still needed work.


Take a look now at the Page Speed Insights report:


Now let’s look at this client’s GTMetrix report:


Which one matters the most? As of Spring, 2021, only the Canary report – unless GTMetrix and Page Speed Insights reports start measuring data and reporting grades in the same way – which will never happen, leaving one or two of these tools obsolete.

Time will tell.


Client Concerns:

For our clients on a full monthly maintenance plan, we spend time working on page speed scores every month.

The challenges are many:

  • Third-party plugins on WordPress websites can weigh down page scores dramatically. Plugins are third party snippets of code. Some plugin developers are good at making “lightweight” plugins, some are not, but for some types of functionality, there may only be one option for a plugin that can provide it. The more plugins, the slower the website might be.
  • Another favorite discussion is with clients that have terrible internet speed where they sit. We have at least two clients who have this issue, but they both know that slow internet is completely different from a slow website. 
  • Home page slides and video – always a favorite among clients because of the visual appeal, and always an impediment to fast page scores. The more slides, the slower the website. eCommerce sites frankly, can do better with two slides than they can with six slides.
  • Adding functionality or features to a site means that page speed score optimization needs to be done again.
  • Clients who “self manage” their websites are especially prone to having page speed issues, largely because they add images that way too big for their web page. While most of our clients don’t do anything more than write blog posts, we still have a couple that tries to economize by managing all of their content. This almost always leads to a bloated site and every-slower page speed scores.
  • Enacting good practices like using a CDN (Content Delivery Network) is a no-brainer because a) it works and b) it’s affordable for every budget. A CDN is mandatory for good page scores, but some clients don’t understand the value. We basically bake this into every service package we sell.
  • Once page speed has been optimized to one measuring tool (whether it’s optimized for a good GTMetrix score, a good Page Speed Insights score, or for a good Canary score), we’ll always have a client who is being told that their page speed score is terrible on one of the other web scoring platforms.



We know that the GTMetrix grading system changed in November of 2020;

Clients are scratching their heads wondering if their web agency has stopped paying attention to their client’s websites;

Page Speed will vary depending on a wide range of changing variables;

Scores are calculated based on the Lighthouse data (to some extent), but GTMetrix’s Grade score is based on how they weigh the importance of the Lighthouse data;

Page speed Insights are helpful and should be reviewed as well;

Canary, Google’s browser and its new Developer tools to measure speed score will be the most important yardstick after it rolls out completely in Spring of 2021;

Page Speed Scores in 2021 are going to be a challenge for many agencies, partially because Google Canary scores will be the only thing that matters and as of this writing, Canary is more of a Beta tool for Developers and most companies will still be using Page Speed Insights or GTMetrix as their barometer;

It will take time to teach clients that Canary is the only measurement tool that matters;



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