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Why Your Website Performance Score May Not Be as Bad as You Think

Google Lighthouse and PageSpeed Insights are the two most common performance score tools used by developers and non-developers to obtain a general idea of how performant a website is. Both of these tools are powered by Google with PageSpeed Insights actually using Lighthouse as its analysis engine.

When you hear that Google is involved, it may automatically increase your confidence that the scores provided ring true, but what you see is not always what you feel. In fact, many large, well-known companies are scoring low for the mobile metric.

One metric simply cannot encapsulate the user experience of any particular website. The performance score is susceptible to variance, based on variables such as device type, network speed, and CPU. How fast a page loads for real users is extremely important, yet defining performance attributes against a linear 0-100 grading scale can be misleading. Despite the inconsistency in performance scores, performance audits are still a great way to determine what changes should be made to improve your website speed. Tools like Google Lighthouse provide a list of best opportunities for improvement. They also identify how much time each issue adds to your load speed. 

How does Google calculate your performance score?

Below are some of the common metrics used by Google Lighthouse and most other website performance auditing tools:

It’s also important to note the weight of the metrics has changed over time and will continue to change to adapt to user-perceived performance. 

What do these metrics represent? 

Simply put, most of these performance metrics equate to speed. When you visit a webpage, your browser sends the request to the server that hosts the page. There are several phases involved in this process, similar to breaking down the steps involved in physically walking into a brick-and-mortar store to browse. 

You park your car, walk to the elevator, choose your floor, walk to the store, open the door, and enter. Even though your goal is simply to walk into the store, any one of the steps in this example can slow you down. Perhaps all of the parking spots are taken. Maybe the elevator is out of service. The store’s door may be locked. Most of these interruptions can be considered minor, and others are certainly cause for concern. 

While there are variables throughout the process of visiting a webpage that can slow you down, many of the steps happen quickly enough to not even notice. Often, we are talking mere milliseconds. The visual below shows a preview of all the individual requests the browser is making to the server for Apple’s homepage. More importantly, it shows that each asset is low in filesize and takes milliseconds to load. 


Desktop vs. Mobile 

More often than not, your mobile score will be drastically lower than the desktop score. By default, Google Lighthouse emulates a Moto G4 using slow 4G throttling. It is safe to say that your Lighthouse mobile scores equate to a worst-case scenario. For context, the Moto G4 is a discontinued phone that was released in 2016. A standard 4G connection averages around 20mbps (megabits per second), which roughly translates to a download speed of 2.5 megabytes-per-second (data transfer rate value divided by 8). The slower simulated 4G throttling provided by Lighthouse, however, runs at approximately 1.6Mbps which translates to 0.20475 megabytes-per-second. 

In other words, the simulated 4G throttling that Lighthouse uses could take close to a full second to download each image on a particular webpage, where standard 4G would be 12 times faster. The more assets a website has on a page, the longer it will take to load, generally speaking. 

The faster the cellular connection, the faster load times will be. In November 2021, T-Mobile reported that 200 million Americans were already using 5G, and that number will continue to increase through 2022. These performance tools have yet to adapt to our current cellular speed.


Your scores will fluctuate 

There are underlying variables that could cause you to score a 53 one day and a 60 the next day.  

Items to consider that lend themselves to Lighthouse score variance according to Google’s

  • A/B testing
  • Differences in ads being served to the page you are testing
  • Internet traffic routing changes
  • Testing on different devices, such as a high-performance desktop and a low-performance laptop
  • Browser extensions that inject JavaScript and add/modify network requests
  • Antivirus software

There are many great performance score tools that can provide insight into your site’s performance, but they should not be held as the final word on the matter. Next time you pull your performance score from Google Lighthouse or PageSpeed Insights, keep these things in mind. 

When should you be concerned about your performance score? 

Like any modern technical undertaking, a methodical and iterative approach should be taken towards your website through testing, user feedback, and as much data as possible. Despite your performance score, if a particular aspect of a page is taking longer than you would expect to load, Google Lighthouse can help you catch the issue. Utilize other tools and resources to gather proper data, remembering common sense and good, old-fashioned intuition goes a long way. 

Your page may be scoring low, and there may be low-hanging opportunities you could address, but there is no need to panic when you see a performance score that’s lower than expected. Performance scores do not affect SEO in and of themselves, but they do affect a user’s experience, which can impact SEO performance. High bounce-rates; user feedback; and visibly slow graphics, videos or other types of content would be cause for concern, but Google Lighthouse is still a valuable resource in your digital bag-of-tricks that help to optimize your website. 

Does the experience of browsing your website indicate subpar performance?  Get professional advice from an expert at Warren Douglas Advertising. It never hurts to have a second or third opinion. Your website is too vital to business to be ignored.

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