Understanding Google’s Page Speed Criteria

Understanding Google’s Page Speed Criteria

Page speed can make or break your website’s user experience. Research suggests that 53% of website users will leave a page if it takes longer than three seconds to load. “The more delay, the more unhappy the user,” says former Developer Programs Tech Lead at Google, Maile Ohye. Conversely, the faster your website loads, the better your users will like it, buy from you, and continue to trust you, as the case may be. What’s more? Page speed is one of the crucial SEO ranking factors.

That’s why Google has continued to implement guidelines on how quickly your site should load and how to improve your site’s page speed. Google PageSpeed Insights has all the KPIs required to track users’ experience with your web pages. You can get a breakdown of each criterion contributing to your webpage’s overall load time score. It also provides suggestions for improving your score in each area.

In this blog, we will discuss the methods, tools, metrics, and criteria required to understand page speed and make it work for you.

Methods and Tools For Understanding Google’s Page Speed Criteria

A good way to begin a discussion about Google’s page speed criteria is by looking at the two ways we can measure page speed: field data and lab data. These two popular scientific methods are adopted by Google to provide insights into web page performance. Each method has specific tools to analyze and report the data. Let’s see how it works.

Lab Data

Lab data is generated from a controlled set of conditions. Here, you can test your site with a tool called Lighthouse. This tool uses automated processes (a set of pre-set networks and device conditions) to simulate real-world usage and measure their results against established standards like those developed by Google’s PageSpeed Insights. The advantage of lab data is that it helps you identify what needs fixing right away so you can focus on the most important elements of your site. However, lab data isn’t always representative of real-world usage because it usually uses a limited set of scenarios that may not represent the actual usage patterns of real users.

Field Data

Field data is gathered by looking at how people interact with your sites in real-world situations. It can be used to understand how fast your website loads from various locations, devices, and connection speeds worldwide. One of the best ways to get quality field data is by running your own tests, though this can be expensive and time-consuming if you don’t have the resources to run your own tests using  Google’s Chrome User Experience Report (CrUX).

What are the Criteria for a Good Page Speed?

1. Image and Text Compression

Compressing images before uploading them to your site will help speed up the loading time of your pages and reduce bandwidth usage, making your site more responsive. For example, in a survey of web pages of business websites by Google in 2017, results show that 30% of web pages could save 250KB by compressing texts and images.

Many tools, such as Shortpixel.com, TinyPNG, and JPEGmini, can help with this task.

2. Code Compression 

This includes using Gzip compression on HTML, CSS, and JavaScript files to reduce file sizes and transfer times without sacrificing content or functionality.

3. Small resource sizes 

Smaller files mean faster downloads and less data usage on mobile devices and desktop computers alike. Smaller files are especially important for mobile websites that need to download over slow connections or pay-per-usage cellular networks worldwide.

4. Minification

Although it was recommended for the older version of Google PageSpeed Insight, minification can still improve a site’s responsiveness today. It involves removing unnecessary characters from code so that it takes up less space when saved, downloaded, or transmitted over the network.

5. Redirects? Avoid it!

A redirect is a way to send visitors from one URL to another. It’s useful when you change your site’s name or URL structure. But if you can avoid using them, do it! Redirects add time and complexity to your site, so if you don’t need one, don’t use it.

 Metrics For Google Page Speed Performance

Google uses the following metrics to determine if your website’s page speed is “good, needs improvement, or poor.” Paying attention to these metrics will help you improve your website’s loading time. These are technically referred to as core web vitals. 

1. First Contentful Paint (FCP)

First, Contentful Paint is a term used in web performance metrics to describe or measure how long it takes for the browser to render the first bit of content on a page. FCP is important because it reveals how quickly the browser can start showing content to users, which means it plays an important role in the perceived speed of your site. A good FCP score, according to Google, is 1.8 seconds or less. Anything over 3 seconds is considered poor.

2. Largest Contentful Paint (LCP) 

The Largest Contentful Paint (LCP) metric reports how long it took for the largest text or image on a page to be displayed. It is considered good if the page takes 2.5 or fewer seconds to load the biggest texts and images. If it takes more than that, there’s a need for improvement.

3. Speed Index

Google uses the Speed Index metric to measure how quickly a page responds to user input. The Speed Index is an aggregated metric that combines data from Chrome User Experience Report (CrUX) with measurements from Lighthouse, a performance auditing tool by Google.

4. First Input Delay (FID)

First Input Delay (FID) is the time it takes for a page to respond to a user’s first action. For example, the FID can be measured as the time between a user’s typing on the keyboard and when they see characters appearing on the screen. It’s important to note that FID is measured by recording users’ actions and comparing them to the time it takes for the page to respond. This means that if your site has any delays, such as a loading video or sound, this will be included in your FID measurement. Google suggests that web admins should keep the FID of their website to 100 milliseconds or less.

5. Interaction to Next Paint (INP) 

The INP metric measures how long it takes for the page to respond to user interaction. It considers all events that cause the browser to repaint and re-layout the page, such as scrolling, clicking, and resizing. When we say “the page responds,” we mean that your layout/rendering engine has updated itself in response to some user action. For example, if you click on a link, there’s a particular time between when you click and when the browser redraws the new content on the screen. Likewise, if you scroll down a page, there’s a certain time between when your finger leaves the trackpad or mouse button and when the browser redraws everything beneath it on the screen. If your page’s INP (Initial Paint) exceeds 200 milliseconds, you should consider improving your web performance.

6. Cumulative Layout Shift 

Cumulative Layout Shift is a metric that analyzes the structural changes of a page. This metric determines if the page has any unexpected layout shifts. For example, the site might have added or removed a feature, but the layout hasn’t changed to reflect that change. This may cause a bad user experience if users try to click on one thing and find another. The idea behind Cumulative Layout Shift is that it’s better for the user experience if little or nothing changes unexpectedly on the screen when they navigate between pages. Therefore, for the best user experience, keeping a low CLS score is essential. Google recommends 0.1.

7. The Time to Interactive

The Time to Interactive metric measures the time it takes for a web page to become usable. It is calculated as the difference between when the browser starts parsing (determining what elements on the page are and how they are structured) and when it renders something on the screen.


Google’s PageSpeed Insights is a set of criteria you can’t ignore. If your website’s performance is directly affected, even the slightest bit, you can definitely do many things to turn things around. However, we suggest that the initial steps you take should follow these three basic guidelines. First, be selective in what you choose to optimize. Second, avoid an excessive number of redirects. Third, always incorporate Google PageSpeed recommendations into your design and performance plans. This will help guarantee that your website performs well on all devices, achieves optimal results in search rankings, and more.