Website Speed Test by Google: How to Check and Improve Your Site
A slow website can frustrate visitors, reduce engagement and make it harder for people to find what they need. Google’s PageSpeed Insights is a free tool that helps website owners assess loading performance and identify opportunities to improve it on mobile and desktop.
What is Google PageSpeed Insights?
PageSpeed Insights analyses a web page and provides performance information alongside suggestions for improvements. You can test a specific page by entering its URL at pagespeed.web.dev. The results include two types of data: real-world user experiences, where available, and results from a simulated test.
Real-user data
Field data is collected from people who have visited the page using Chrome. It can show how the page performs for actual users across different devices and network conditions. This data may not appear for every URL, particularly if the page does not have enough eligible visits. In some cases, PageSpeed Insights may show data for the wider website instead.
Lab data
Lab data comes from a controlled Lighthouse test. It provides a repeatable snapshot of the page and can help developers investigate performance issues. Because it is simulated, it may not match every visitor’s experience. Results can also vary between tests due to network conditions, server response times and changes to the page.
Understanding the main speed and experience metrics
PageSpeed Insights reports on several measures of loading speed and usability. Three important Core Web Vitals are:
- Largest Contentful Paint (LCP): how long it takes for the main visible content to load. A good result is 2.5 seconds or less.
- Interaction to Next Paint (INP): how quickly the page responds visually to a user’s interactions. A good result is 200 milliseconds or less.
- Cumulative Layout Shift (CLS): how much the page layout moves unexpectedly as it loads. A good result is a score of 0.1 or less.
These thresholds are assessed using real-user data, generally at the 75th percentile. This means a good result indicates that at least three out of four visits meet the relevant threshold.
The Lighthouse performance score is a separate, weighted score based on lab metrics. It is useful for spotting issues, but it is not a complete measure of a website’s quality. A high score does not guarantee that every visitor will have a fast experience, and a lower score does not explain every cause of poor performance on its own.
How to run a Google website speed test
- Open PageSpeed Insights.
- Enter the full URL of the page you want to test.
- Select the mobile or desktop results.
- Review the performance score, Core Web Vitals and diagnostic recommendations.
- Make improvements, then test the page again.
Test important pages individually, such as the home page, product pages, articles and contact pages. A website can perform well on one page and poorly on another because they use different images, scripts, layouts or third-party services.
Common ways to improve website speed
Optimise images
Large images are a frequent cause of slow loading. Resize images to suit their display dimensions, compress them and consider modern formats such as WebP or AVIF. Add image dimensions to help prevent layout shifts, and lazy-load images that appear further down the page. The main image near the top of the page should not usually be lazy-loaded.
Reduce unnecessary JavaScript
Scripts can delay loading and make pages slower to respond. Remove code that is no longer needed, limit non-essential third-party tools and defer scripts that are not required straight away. Changes should be tested carefully to make sure site features still work.
Improve server response times
Slow hosting, inefficient database queries and a lack of caching can delay the start of page loading. Server-side caching, a content delivery network (CDN) and suitable hosting can help deliver content more quickly, particularly to visitors who are far from the server.
Prevent unexpected layout shifts
Reserve space for images, adverts and embedded content so that the page does not jump as these elements load. Avoid inserting content above existing content without a user action, and check that fonts do not cause the layout to shift noticeably.
Review fonts and third-party services
Web fonts, analytics, advertising and social media widgets can add extra requests and processing. Use only the fonts and services that are needed, and load non-essential resources in a way that does not block the main content.
Does a PageSpeed Insights score affect Google rankings?
Page experience and Core Web Vitals can be considered among many factors in Google Search. However, there is no single PageSpeed Insights score that guarantees a particular ranking. Relevant, helpful content remains important, and improving a score alone does not ensure better search visibility.
Use the results as a guide
A Google website speed test is a useful starting point, not a substitute for testing with real visitors and devices. Focus first on issues that affect the main content and user interactions, then monitor real-user performance over time. Consistent improvements to speed and stability can make a site more pleasant to use for everyone.
5 Tips for Testing and Improving Website Speed with Google PageSpeed Insights
- Use Google PageSpeed Insights to test mobile and desktop performance.
- Test key pages, not just the homepage.
- Fix high-impact issues such as slow server response and render-blocking resources.
- Compress images and use modern formats such as WebP.
- Retest after changes and track Core Web Vitals over time.
Use Google PageSpeed Insights to test mobile and desktop performance.
Use Google PageSpeed Insights to check how your website performs on both mobile and desktop devices. Enter the page URL to see performance results, real-user data where available, and recommendations for improvements. Test key pages separately, as their content and features can affect loading speed differently. Treat the results as a guide: fixing the most important issues can help create a faster, smoother experience for visitors.
Test key pages, not just the homepage.
Test key pages, not just the homepage, because each page may use different images, scripts, layouts and features that affect loading speed. Check important examples such as product pages, articles, landing pages and the checkout, on both mobile and desktop. This gives you a clearer picture of how visitors experience the whole website and helps you prioritise fixes where they matter most.
Fix high-impact issues such as slow server response and render-blocking resources.
When using Google’s website speed test, start with high-impact issues that delay the page for many visitors. A slow server response can hold up everything that follows, so review your hosting, caching and server-side processing. Render-blocking resources, such as CSS and JavaScript, can also prevent content from appearing promptly; remove unnecessary files, defer non-critical scripts and optimise how stylesheets are delivered. Re-test the page after each change to see whether loading performance has improved.
Compress images and use modern formats such as WebP.
Compressing images is one of the simplest ways to improve your website’s speed test results. Large image files take longer to download, particularly on mobile connections, so resize them to fit their display dimensions and reduce their file size without noticeably affecting quality. Where supported, use modern formats such as WebP, which can provide smaller files than traditional formats like JPEG and PNG. Be sure to keep image dimensions specified in your page code to help prevent the layout shifting while images load.
Retest after changes and track Core Web Vitals over time.
After making changes to your website, run the Google PageSpeed Insights test again to check whether they have improved performance. As results can vary, avoid relying on a single test: monitor your Core Web Vitals over time using real-user data, where available. Regular checks can reveal regressions and help you spot issues before they affect more visitors.
Leave a Reply