TLDR: Google PageSpeed Insights (PSI) is a free tool from Google that analyses how quickly your web pages load and how they perform on mobile and desktop. It gives you a performance score based on key speed and UX metrics, highlights specific issues, and offers practical suggestions for improvement. Whether you’re a developer, marketer, or site owner, it’s a must-use tool for enhancing user experience and SEO.
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A guide to Google PageSpeed Insights
A slow-loading website can frustrate visitors, increase bounce rates, and even lower your rankings in search engines. Fortunately, Google provides a powerful (and free) tool to help you diagnose speed issues and fix them: Google PageSpeed Insights (PSI).
This guide walks you through everything you need to know about PageSpeed Insights, what it is, how to use it, how to understand the results, and how to improve your score.
What is Google PageSpeed Insights?
Google PageSpeed Insights is an online tool that analyses the performance of your web pages. It looks at how fast your site loads and how well it performs from both a user experience and technical standpoint. The tool provides a performance score, color-coded results (green for good, orange for needs improvement, red for poor), and detailed recommendations for fixes.
What makes PSI especially valuable is that it presents this information in a simple, visual format that’s accessible to everyone, from tech-savvy developers to business owners who just want their website to run smoothly. While PageSpeed Insights is more user-friendly and accessible than Lighthouse, it actually runs Lighthouse under the hood to generate its lab data. It’s not a separate tool in terms of technology, PSI is essentially a frontend wrapper around Lighthouse, enhanced with real-world (field) data from the Chrome User Experience Report.
How does Google PageSpeed Insights work?
Using PageSpeed Insights is as easy as entering your URL and clicking a button. Behind the scenes, though, it’s doing a lot of work. The tool simulates how your page performs under different network conditions and device types. It then generates a score based on several key performance metrics, including both lab data (collected in a controlled environment) and field data (from real users using Chrome across the web).
This combination of lab and field data gives you a more complete picture. You get a snapshot of what a new visitor might experience, along with insights into how real users have interacted with your site over the last 28 days.
Step-by-Step: Entering a URL and running an analysis
To get started, head to https://pagespeed.web.dev. You’ll see a single input field. Just paste in the URL of the page you want to test, whether that’s your homepage, a product page, or even a blog post. Once you click “Analyse,” PSI gets to work, running tests and compiling the results in just a few seconds.
You’ll get two sets of results: one for mobile and one for desktop. This is important because users often have very different experiences depending on their device. Mobile users might be dealing with slower connections or smaller screens, which can affect how fast your site feels to them.
Interpreting the performance score
After the analysis runs, the first thing you’ll see is your performance score. This is a number from 0 to 100 that reflects how quickly your page loads and becomes usable. A score of 90 or above is considered good, while anything under 50 usually indicates major issues.
Beneath the score, PSI breaks down individual areas that contribute to your performance, including things like accessibility, SEO basics, and best practices. What’s especially helpful is that each section is expandable. You can click to dive deeper and see which parts of your site are slowing things down, sometimes even pinpointing the exact lines of code that need attention.
Distinction between mobile and desktop results
PageSpeed Insights provides separate tabs for mobile and desktop results. This isn’t just a design feature, it’s critical for understanding how different users experience your site. Mobile users might encounter slower loading times due to network conditions or heavier resource usage on smaller devices. Conversely, desktop users might benefit from faster Wi-Fi and better processors.
Being able to easily toggle between the two views means you can optimize your site with a full picture of your audience’s experience. If your mobile score is dramatically lower than your desktop score, that’s a signal that you need to prioritise mobile optimisation.
Understanding the key metrics
Core Web Vitals: LCP, INP, and CLS
Google’s Core Web Vitals are at the heart of your performance score. These three metrics are especially important because they focus on user experience:
- LCP (Largest Contentful Paint) measures how long it takes for the main content of the page to load. Ideally, this should happen within 2.5 seconds.
- INP (Interaction to Next Paint), which is replacing FID (First Input Delay), evaluates how responsive your page is to user input. Like clicking a button or filling out a form.
- CLS (Cumulative Layout Shift) tracks visual stability, showing whether content shifts unexpectedly while loading (like buttons jumping around). A good CLS score is under 0.1.
Each of these metrics contributes significantly to how smooth and fast your site feels for users.
Other metrics: TTFB, FCP, TTI, and Speed Index
Beyond the Core Web Vitals, there are other helpful indicators:
- TTFB (Time to First Byte) tells you how long it takes for your server to respond to a user’s request.
- FCP (First Contentful Paint) measures when the first text or image is rendered.
- TTI (Time to Interactive) evaluates how long it takes for your page to become fully interactive.
- Speed Index summarises how quickly your content is visually displayed.
Together, these metrics paint a detailed picture of your page’s loading performance from both a technical and user perspective.
How to improve your Google PageSpeed score
Improving your score isn’t about chasing 100. It’s more important to make enhancements to your users’ experience. And luckily, PSI doesn’t just highlight what’s wrong, it also suggests how to fix it.
Common issues and how to fix them
One of the most common performance killers is image size. Uncompressed or oversized images can dramatically slow your site down. By compressing images, using modern formats like WebP, and serving appropriately sized images, you can make a huge difference.
Another area to focus on is minifying code. Removing unnecessary characters and whitespace from your CSS, JavaScript, and HTML files helps reduce page weight and speeds up load time.
If your site is slow to respond initially, it may be due to server response time. This can be improved with better hosting, database optimisation, or server-side caching.
Lazy loading is another smart strategy, it defers loading images and other media until the user actually scrolls to them, which can significantly speed up the initial load.
To go a step further, consider using caching and a content delivery network (CDN). These tools help store versions of your site closer to users and reduce the time it takes to load pages.
And remember, you should always evaluate your site’s mobile and desktop performance separately. Mobile optimisation often involves more aggressive strategies, like reducing script usage or eliminating large pop-ups that block content.
Google PageSpeed Insights vs Google Lighthouse
While both tools are powerful, they serve slightly different purposes.
Google PageSpeed Insights combines both lab and real-world data, making it an excellent choice for marketers, SEOs, and business owners who want a high-level understanding of how users are experiencing their site. It’s faster to use, easier to understand, and perfect for quickly auditing different page types.
Google Lighthouse, on the other hand, is more technical and runs within your browser’s developer tools. It provides a deep dive into lab-based data under simulated conditions, which is ideal for developers or technical teams who want a controlled, consistent environment for testing.
In short: use PageSpeed Insights for real-world performance and user-focused audits, and Lighthouse for in-depth, developer-level optimisation.
Final thoughts
Page speed is a core part of your website’s success when running audits on pages. Google PageSpeed Insights makes it easy to identify slowdowns and fix them with confidence. Whether you’re tweaking a single product page or optimising an entire eCommerce store, PSI gives you clear, actionable insights to improve both user experience and SEO performance. Want to see how your site stacks up? Get in touch with our team today and start making Google PageSpeed Insights work harder for your business.
