Site speed can undermine your entire online strategy. Start tracking it everyday!

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Speed impacts customer experience, operational costs and returns, but is still treated as an afterthought even today.

Nobody likes a slow website. Convenience is one of the top reasons why people buy online. A slow experience is the equivalent to a long line at the payment counter and nobody likes to queue. Therefore, at the slightest sign of friction your users leave and may never return. In fact, potential customers often form an opinion about an entire company based on their website and how quickly it loads. To make matters even worse, users remember online loading times as being, on average, 35% longer that they actually are.


Nothing of the above is probably news to you. The internet is filled with articles, checklists and best practices guides since Google announced it would be considering speed as a relevant signal for its ranking algorithm almost a decade ago. Yet, when there is a chance to accommodate a better aesthetic, new neat functionality or new content, speed gets sidelined. 


What makes this issue even more problematic is that how a site functions in development is often quite different from how users experience it. Personalized or third-party content often doesn't behave the same in development as it does in production, test images are often already in the developer's browser cache, and API calls that run locally are often so fast that the delay isn't noticeable.


The hard truth is that users care more about speed than all bells and whistles on your website. Your business will lose Sales, spend more on paid media, spend more on back end infrastructure due to low performance. In the end your Returns will have a major set back.


In this article we will use Google's recent announcement on page experience to go through core speed metrics, why you should keep track of them on a regular basis on all your landing pages and how a sluggish online experience may be costing your business a lot of money.


Performance Metrics to keep under regular surveillance


What is a site speed and how to measure it? In simpler times, loading time (meaning the time a page takes to fully load all its elements) was the mantra and developers and web designers raced to optimize backends and squeeze every drop of capacity from their servers. It was an appealing metric, both simple to understand and straightforward to measure. 


The problem is that Humans and Machines do not perceive time in a similar fashion. Time is relative, or as  Albert Einstein's puts it: “ when you are courting a nice girl an hour seems like a second. When you sit on a red-hot cinder a second seems like an hour. That’s relativity”. In other words, time flies when you are having a fun experience but it drags while waiting between loading screens. Page Load Times does consider how long it takes to load and not how it loads. 


Like in all things concerning the Internet, Google has been setting the tone and standards when it comes to performance and experience. During the announcement of its latest lighthouse revision Google unveiled new performance metrics and weight distribution.



Phase V6

Weight V6

Phase V5

Weight V5

FCP (First Contentful Paint)





SI (Speed Index)





LCP (Largest Contentful Paint)





TTI (Time to Interactive)





TBT (Total Blocking Time)

Main Thread




CLS (Cumulative Layout Shift)





FMP (First Meaningful Paint)





FCI (First CPU Idle)






Some are old friends but there are some new additions. Before we go through each individual metric notice the weight change. Google is now prioritizing frictionless navigation by increasing the combined weight of the medium and main thread navigation. This change will have a significant impact on how pages rank and may prove to be a milestone for online performance. 


Additionally Google promoted three key metrics and will include them as signals for the foreseen Rank Search Algorithm version to be deployed in the near future. They are called Core Web Vitals and include Largest Content Paint (LCP), First Contentful Paint (FCP) and Cumulative Layout Shift (CLS). It’s an effort to raise web developers' awareness of core user experience needs as loading experience, interactivity and visual stability of page content.


Largest Contentful Paint

according to Google, LCP measures perceived load speed and marks the point in the page load timeline when the page’s main content has likely loaded. In practice, in order to approximate when the main content is visible to users it measures when the largest content element in the viewport is rendered to the screen. It’s a metric for perception of speed. Even if some elements are still loading once a significant part is loaded users consider the page to be ready to interact with.


First Input Delay:

according to Google, FID measures responsiveness and quantifies the experience users feel when trying to first interact with the page. In simple terms think of this as a first impressions metric. Although part of the Core Web Vitals, you won’t find this metric on the table above because it is in fact a combination of two separate metrics, one to measure the impression of load speed (First Contentful Paint) and one for sites

interactivity (Time to Interactivity).


First Contentful Paint:

Marks the time at which the first text or image is painted. FCP measures how long it takes the browser to render the first piece of DOM content after a user navigates to your page. Images, non-white <canvas> elements, and SVGs on your page are considered DOM content; anything inside an iframe isn't included. 


Time to Interactive

Measures the amount of time it takes for the page to become fully interactive. Measuring TTI is important because some sites optimize content visibility at the expense of interactivity. This can create a frustrating user experience: the site appears to be ready, but when the user tries to interact with it, nothing happens.


Cumulative Layout Shift:

Measures visual stability and quantifies the amount of unexpected layout shift of visible page content. Because nowadays so much content is loaded dynamically changes can trigger unexpected behaviors on DOM elements which may puzzle the user and spoil his experience. Think off all those annoying buttons which tend to change places every time you try to press it.


Speed Index:

measures  how quickly the contents of a page are visibly populated. Speed Index measures how quickly content is visually displayed during page load. 


Total Blocking Time:

Sum of all time periods between FCP and Time to Interactive, when task length exceeded 50ms, expressed in milliseconds. TBT measures the total amount of time that a page is blocked from responding to user input, such as mouse clicks, screen taps, or keyboard presses.



Green (fast)

Orange (moderate)

Red (slow)

LCP time (in seconds)



4 <

FCP time (in seconds)



4 <

TTI metric (in seconds)



7.3 <

CLS metric 



0.25 <

SI (in seconds for mobile)



5.8 <

TBT time (in milliseconds)



600 <


Why is performance draining your resources?


Now that we have quickly covered the main performance metrics used by Google, let's talk business. But first let’s address the elephant in the room. Yes, content is still king. Google claims to prioritize useful information over experience. “While all of the components of page experience are important, we will prioritize pages with the best information overall, even if some aspects of page experience are subpar. A good page experience doesn’t override having great, relevant content. However, in cases where there are multiple pages that have similar content, page experience becomes much more important for visibility in Search. ” according to their latest announcement


But as most e-commerce and online business managers and executives know, SEO is just a part of the equation. Stressed by fierce competition and meager margins, they know that scale matters and a single misstep can put them out of business. 


Here follow 4 negative impacts on your business caused by a crawling website or page performance:


First, your paid media strategy will cost you mor


Sluggish landing pages have lower Quality Scores. And Quality Scores will determine when and if your AD will appear to potential customers and its cost. The lower  the performance the higher the Premium paid and less air time will be given to your AD. Higher Quality Scores allow for lower bids for higher positions reducing the Cost Per Click (CPC).


Second, your organic search strategy gets penalized


Slow pages have higher bounce rates. For search engines algorithms this is a signal for low value content. Because search engines want to serve the most relevant content on any query, your page will be penalized and shown to less potential customers. All your team effort towards optimizing SEO goes instantaneously down the drain.


To make matters worse, Search Engines Crawlers spend a limited time on each site. In the eventuality your entire website is slow to respond, then the bot will only index a limited number of pages.


Third, your customers will buy less 


It is frustrating and painful to watch the extent that many companies go to get potential customers to click on their website just to see them bounce because they are not willing to wait for a page to load.


From our experience a reduction of 7 seconds on a metric as speed index reduced a financial client bounce rate by around 18%. This highlights how 1 second could make all the difference in the world between a successful transaction and a very poor interaction.


Fourth, your investment on new tools will backfire


Analytics tools, automation platforms and dynamic content providers all rely on additional JS code which will run during page load. On an already slow page, this will just exacerbate the problem. Instead of helping your site provide a better customer experience, these tools will end up doing exactly the opposite.


Fifth, you will end up spending more on infrastructure


To better grasp the impacts of speed on your infrastructure let’s compare two pages with very different metrics. 



Page A

Page B

Largest Content Paint (LCP)

5 s

2 s

First Content Paint (FCP)

5 s

2 s

Time CPU core busy

10 s

4 s

Requests server CORE/Minute



Number of CORES available



Number of requests server in Minute (A)



Total clicks per minute (B)

1,33 (1 every 45s)

1,33 (1 every 45s)

Total simultaneous users (A*1/B)




Using both LCP and FCP as proxy for request time the simple calculation provides us with a sense of how speed impacts our backend infrastructure. Compared to Page B, Page A owners would have to double their infrastructure to handle similar traffic. Of course the age of cheap and pay on demand computing allows developers to answer peaks on the fly, but all this comes with a price tag associated. When businesses fail to optimize the use of their online resources they forsake one of their main advantages against their brick and mortar competitors, economies of scale. 


How can we help you track your website speed? 


There are a variety of available tools online to track page performance, and most of them are free. Lighthouse is Google’s own set of tools and is one of the most widely used. But the majority of this tools have two major drawbacks: 1) they only measure performance one page at a time and 2) they only measure it at a specific moment in time. 


Websites today are a complex net of gateways and landing pages making it useless to monitor just one page. Your main landing page can be top notch, but if most of your traffic is coming through lagging campaign specific landing pages all your efforts are in vain.


That's why we at Math Marketing developed our own solutions that we deploy on all our customers and which we called BOLT. Bolt monitors performance metrics in real time for a variety of pages simultaneously helping teams track their website performance. Bolt is customizable to our customers specific needs and can be delivered to any analytics tool your team uses such as Power BI, Data Studio or our own proprietary platform.


Are you interested in knowing more? Schedule a Demo for 3 months with our team. Our colleagues Lucas Ferreira de Souza and Carlos Ronaldo Cardoso would gladly walk you over our tool functionality and the setup project.



Math Marketing helps companies from a variety of industries to implement Data Driven processes. By mixing statistical proficiency, business knowledge and advanced tools we help our customers answer tough questions. Some of the largest brands share with us their data challenges, and trust our data generated insights on everyday operational and strategic decisions.


If you want to learn about our projects and methodology reach us over the e-mail or contact any of our team managers directly on Linkedin. We are always available to share our insights with you and listen to your experience.



Pedro Magalhães - Head of Marketing Engineering @ Math Marketing EMEA - Follow me on Linkedin

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