How to Test Your Website’s Page Speed

A fast website makes it easier for visitors to find information, complete purchases and enjoy a smooth browsing experience. Slow pages can frustrate users, particularly on mobile devices or unreliable connections. Testing your website’s page speed helps you spot problems and decide what to improve.

Choose the right speed-testing tools

Several tools can help you assess a website’s performance. Each provides a slightly different view, so using more than one can give you a clearer picture.

• Google PageSpeed Insights: Tests a page on mobile and desktop, with real-user data where available and recommendations for improvements.
• Lighthouse: An auditing tool built into Chrome DevTools. It runs simulated tests and reports on performance and other aspects of page quality.
• WebPageTest: Offers detailed test settings, including the location, browser and connection speed used to load a page.
• Chrome DevTools: Helps developers inspect loading behaviour, network requests and performance issues directly in the browser.

Understand the key measurements

A page-speed report contains several measurements. The most useful indicators of user experience include Google’s Core Web Vitals:

• Largest Contentful Paint (LCP): Measures how long it takes for the main content to appear. A good result is 2.5 seconds or less.
• Interaction to Next Paint (INP): Measures how quickly a page responds to user interactions. Aim for 200 milliseconds or less.
• Cumulative Layout Shift (CLS): Measures unexpected movement of page elements. A good score is 0.1 or less.

Other figures, such as Time to First Byte (TTFB), can help diagnose server delays. Treat individual scores as clues rather than the whole story: the experience visitors have is more important than achieving a perfect score.

How to test a page

1. Choose an important URL. Test the homepage, but also check key pages such as product listings, articles, contact forms and checkout pages. Different templates can have different performance problems.
2. Run mobile and desktop tests. Mobile tests often use a slower connection and less powerful device, which can reveal issues that are less obvious on a computer.
3. Repeat the test. Results can vary with network conditions, server load and the testing tool. Run several tests and look for consistent patterns.
4. Review field and lab data. Lab tests simulate a visit in controlled conditions. Field data reflects the experience of real visitors, where available. Both are useful, but they answer different questions.
5. Record the results. Note the page, date, device setting and main measurements. This makes it easier to see whether changes have helped.

What to improve when a page is slow

Speed reports often identify specific opportunities. Common improvements include:

• Compressing images and serving them in modern formats where supported.
• Loading images only when they are close to appearing on screen.
• Reducing unnecessary JavaScript and CSS, and removing unused code.
• Improving server response times and using caching appropriately.
• Limiting third-party scripts, such as advertising, analytics and embedded content.
• Setting image dimensions to prevent content from shifting as a page loads.
• Using a content delivery network (CDN) where it suits the site and its audience.

Prioritise changes that address the biggest problems on important pages. Make one set of changes at a time, then test again. This helps you understand which improvements made a difference and reduces the risk of introducing new issues.

Make speed testing a regular habit

Website performance can change when new images, features, plugins or scripts are added. Test important pages after significant updates, and include performance checks in your regular maintenance routine. By combining reliable testing with steady improvements, you can make your website faster and more pleasant to use.