Is Google PageSpeed Insights Reliable?

on 18 Aug 2023, by Bogdan, in Blog, WordPress, Cloud, Guides

by Bogdan

User experience is crucial to the success of your website, and you should measure and constantly improve it. Google Page Speed Insights is highly regarded as a useful tool for evaluating user experience by measuring specific metrics that determine it.

However, if you’re new to it, it is perfectly reasonable to ask the question ‘Is Google PageSpeed Insights reliable?’. In this post, we’ll answer this question comprehensively as we look at what this tool is and how to use it.

What is Google PageSpeed Insights?

Google PageSpeed Insights (PSI) reports on real user experiences with your website on both mobile and desktop versions. It then provides suggestions on how you can improve that page to boost your site’s performance and user-friendliness.

Additionally, PSI also uses free, open-source Lighthouse to analyze your site’s URL in a simulated environment. It tests your site’s performance, accessibility, best practices, and SEO. At the top of the report section, are scores for each category, determined by running Lighthouse to collect and analyze diagnostic information about your web page.

How to use Google PageSpeed Insights

Using Google PageSpeed Insights is straightforward. Simply, go to PageSpeed Insights and enter your site’s URL. Then, click the Analyze button to run the analysis. Two things occur at this stage:

Google PageSpeed Insights checks for your website in the Chrome user experience (CrUX) dataset to prepare performance reports based on real user experience data.
PageSpeed Insights starts loading your website on Google servers using Lighthouse.

This should only take a few seconds depending on your site’s complexity and your internet connection speed

Once the analysis is complete, you will receive a performance report that includes your site’s overall score for mobile and desktop versions. You will be able to see information on real user experiences on your website (the field data report). You will also see a more detailed breakdown report on your site’s performance issues and identify potential opportunities for improvements.

Let’s take a closer look at PageSpeed Insights’ performance report and see what you can learn from it.

Understanding Google PageSpeed Insights performance report

At first glance, the Google PageSpeed Insights performance report is neatly organized into two primary sections. These include the field data and the lab data sections.

1: Field data section: Core Web Vitals assessment

In this initial section of the report, Google PSI focuses on the experiences a subgroup of users have had as they interact with your website. This real-user information comes from users who actively use Google Chrome and have willingly consented to share their internet usage patterns (CrUX database).

Important: This section excludes information about people using Firefox, Chrome on iOS, among others.

This information forms the basis for PSI insights, and it is typically not older than about 28 days. This section will give you a clear, accurate picture of real users' interaction with your website.

At the top, you will see if you passed or failed the Core Web Vitals assessment

Google PSI reports the following real user’s core web vitals experiences over the previous 28-day collection period:
Largest Contentful Paint (LCP) – This metric measures your site’s loading performance. It checks how quickly the largest piece of content on your page, like a picture or video, shows up when a user opens up your page.
First Input Delay (FID) – This metric assesses your site’s interactivity, and how fast your website responds when someone tries to do something on it, like clicking a button or a link.
It measures if there's any delay between when someone clicks and when your website actually does something in response. (This will be replaced in March 2024 by Interaction to Next Paint (INP)).
Cumulative Layout Shift (CLS) – This metric measures a site’s stability. It looks out for elements/components that move around unexpectedly when someone is using it.

(Accessing quality of experiences: PageSpeed Insights)

Other notable core web vitals include First Contentful Paint (FCP), Interaction to Next Paint (INP), and Time to First Byte (TTFB) measures the following respectively:

How fast above-the-fold content appears on your webpage. It gives an idea of how quickly visitors see something happening when they land on your site.
How long it takes for your website to react after someone interacts with it. Interaction to Next Paint (INP) measures site interactivity just as the First Input Delay (FID).
How quickly your website starts loading on a browser after someone asks to see it.

2: Lab data section – Diagnoses performance issues

Directly below the Core web vitals assessment section is the diagnose performance issues section. This section entails a controlled analysis report of your website's loading speed on the Google server.

For this, Google PageSpeed Insights uses Lighthouse-simulated throttling to run a page load simulation on your website on a single device and a fixed set of network conditions. The simulation is first done on a fast network connection. After which, another simulation is performed on a slower network connection.

The performance category has the page's performance on different metrics, including First Contentful Paint (FCP), Largest Contentful Paint (LCP), CLS, speed index, Time to Interactive, and Total Blocking Time. Apart from testing site performance on Lighthouse, this section also audits the following categories:

Accessibility – This audit assesses factors such as alt text for images, ease of navigation, color contrast for users with visual impairments, audio and video, touchpoints, and much more.
Best practices – This check evaluates how well your site adheres to the general standards(or set of guidelines) for website development. These include things like secure connections, optimized code, etc. It also highlights the opportunities to improve the overall code health of your website/app.
Search engine optimization (SEO) – This audit focuses on whether your website is optimized for search engines. It checks if it follows Google’s basic search engine guidelines.

Note: The performance score on PageSpeed Insights is part of Google’s SEO strategy. The score achieved indicates whether your pages meet Google’s performance and speed standards or not, and this will impact how Google ranks you on its search engine. Therefore, you should treat it as such. If you get good scores across all three Core Web Vitals metrics (LCP, FID, CLS) this will help your SEO keyword rankings.

What is a good PageSpeed Insights Score?

A good performance score in Google PageSpeed Insights falls between 90 and 100. But having this score doesn't guarantee a perfect user experience. Users can still have a good experience on your website even if your performance score is 50 or lower.

When using Google PSI, your main goal should be to make your pages work well for most users. If you can aim for the 75th percentile value for PSI metrics, then the majority of your site users will definitely have a good experience on your website. This is true even if they’re connected to a poor network or use slow devices.

Otherwise, 50 to 89 is a score that needs improvement, and below 50 is considered poor. Fortunately, Google offers recommendations on how to improve your site for the best performance score. These recommendations are what PageSpeed Insights refer to as opportunities.

Note: Opportunities are a list of suggestions that PageSpeed Insights provides to enable you to optimize your overall site’s performance and user experience. It also includes the expected result (estimated savings) when those recommendations are applied appropriately.

Having looked at the field data and lab data performance reports separately, let’s now answer the question that’s been lingering in our minds to this point.

Is Google PageSpeed Insights reliable?

Generally speaking, Google PageSpeed Insights is a reliable tool for testing the performance of your website. This is because Google PSI provides a complete set of all the performance data gathered from users who have visited your site over a 28-day period.

When you examine closely any CrUX report, you’ll notice that some users who visit a site might have a very good experience while others might have a very poor experience. The primary focus of Google PageSpeed Insights, as mentioned earlier, is to ensure that your pages work well for the majority of users. It helps you achieve this by providing you with well-rounded, practical suggestions and insights that are more aligned with real-world user experiences.

However, it’s also important to note that the data from lab testing and actual field use can sometimes contradict each other. This is usually because of the predefined set of network and device conditions that are set up for collecting performance data during lab tests. Lab data is typically derived from tests on a single device, a single network connection, and a single geographical location. Therefore, the specifics of any given lab test may or may not accurately represent what most people experience on your site

How to improve your Google PageSpeed Insights score?

You can improve your PSI scores by implementing Google PSI’s suggestions listed in the opportunities section. These include:

Eliminating render-blocking resources – for example, by reducing CSS and JavaScript, deferring non-critical resources, minifying CSS/JS, etc.
Reduce server response time (TTFB) – This is the time it takes for the browser to receive the first byte of data from the server.
Optimize your images properly. For instance, you can use priority hints to load your main image faster, defer offscreen images, etc.
Reduce Document Object Model (DOM) size,
Avoid unnecessary server connections, preload key requests,
and much more.

Applying these suggestions correctly to your website will increase your Google PageSpeed Insights score.

Brizy Cloud is already optimized for impressive Google Speed Insights scores.

Brizy Cloud is built with a focus on delivering fast-loading and responsive websites. The platform employs various techniques and coding practices to minimize loading times, reduce server requests, and optimize website assets, resulting in better overall performance. This is crucial as faster-loading websites enhance user experience, improve search engine rankings, and increase user engagement.

Learn how Brizy Cloud improves your Google Speed Insights score (and not only GSI) by reading this blog post here

Wrapping up

The reliability of Google PageSpeed Inisghts is grounded in its ability to assess website performance through real user data gathered over a 28-day period. It gives practical, real-world insights and suggestions that if you correctly implement on your website will improve its overall performance and more so, the user experience on your website.

But remember, the lab tests might not match real-user experiences because it is conducted in a controlled lab environment. As such, while PageSpeed Insights offers a solid starting point for understanding your website's performance, it may not be the only tool you should rely on.

Article by Bogdan

Co-founder & Head of Design, Bogdan has a passion for everything that works great and looks awesome. Guilty for most of the UI and UX around this place, you can say "Hi" to him at bogdan at brizy dot io