Your website may feel fast when you open it yourself, but your customers might experience something completely different. A good place to begin is GTmetrix, which gives you a quick overview of loading performance and technical bottlenecks. At Dune Seed, we tell you how to check website speed.
Your own browser may have cached files, your internet connection may be faster than your customers’, and your device may be more powerful. To understand whether a website is genuinely fast, you need reliable testing tools, mobile performance data, and real-user metrics.
Start With a Quick GTmetrix Test
GTmetrix helps you get an initial picture of how a page loads. Enter your website URL, run the test, and review the GTmetrix Grade, Performance score, Structure score, Web Vitals, total page size, requests, and loading visualization.
Its Waterfall chart is particularly useful when troubleshooting. It shows individual page resources in loading order, helping you identify slow images, scripts, stylesheets, third-party services, failed requests, or resources that block other content. GTmetrix also uses Lighthouse-based audits and can display Chrome User Experience Report data when sufficient real-user data exists.
Why PageSpeed Insights Should Be Your Main Speed Test
GTmetrix is excellent for diagnosis, but Google PageSpeed Insights should be one of your primary tools when evaluating website performance for SEO and user experience.
PageSpeed Insights combines Lighthouse lab testing with real-world Chrome User Experience Report data when available. This makes it useful for understanding both technical performance in a controlled environment and how actual Chrome users experience your website.
How to Test Your Website With Google PageSpeed Insights
Go to Google PageSpeed Insights and enter the URL you want to analyze. Do not test only your homepage. Your service pages, landing pages, product pages, and high-traffic articles may use different images, scripts, layouts, plugins, and tracking tools.
After the analysis finishes, examine both Mobile and Desktop results. Start with the user-experience data near the top when available, then review the Lighthouse performance section and diagnostic recommendations further down the report.
Check Mobile Performance First
Mobile results deserve special attention because smartphones usually have less processing power than desktop computers and visitors may use slower or unstable connections.
Heavy JavaScript, oversized images, page builders, advertising scripts, analytics platforms, and third-party widgets often create a larger performance impact on mobile. A site that feels instant on your office laptop can therefore feel frustratingly slow on a customer’s phone.
Understand Your PageSpeed Performance Score
PageSpeed Insights gives your page a Lighthouse Performance score from 0 to 100. This score provides a useful overview of laboratory performance, but it should not become the only number you optimize.
A score of 100 is not necessary for every successful website. More importantly, the Performance score is based on a controlled test, while real visitors use different devices and network conditions. Use the score to identify technical weaknesses and measure progress rather than treating it as the complete definition of website speed.
Focus on the Three Core Web Vitals
Google’s current Core Web Vitals measure three important aspects of user experience: loading, responsiveness, and visual stability. The metrics are Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS).
| Metric | What It Measures | Good Target |
|---|---|---|
| LCP | Loading performance | ≤ 2.5 seconds |
| INP | Interaction responsiveness | ≤ 200 ms |
| CLS | Visual stability | ≤ 0.1 |
Largest Contentful Paint
LCP measures how long it takes for the main visible content to appear. This is often a hero image, banner, heading area, or another large element above the fold.
If your LCP is slow, investigate server response time, large hero images, CSS delivery, caching, fonts, CDN configuration, and resources that delay important content.
Interaction to Next Paint
INP measures how quickly the page responds visually after a visitor interacts with it.
A page might load quickly but still feel slow when users open a menu, click a button, select a filter, or interact with a form. Heavy JavaScript, long browser tasks, complex plugins, and third-party scripts commonly contribute to poor responsiveness.
Cumulative Layout Shift
CLS measures unexpected movement of visible page elements.
For example, a visitor may try to click a button only for an advertisement, image, font, or banner to suddenly move the layout. Reserving dimensions for images and embeds and controlling dynamically inserted content can help reduce these shifts.
Field Data vs. Lab Data
Understanding field data and lab data prevents one of the most common mistakes in website performance analysis.
| Data Type | What It Represents | Best Use |
|---|---|---|
| Field Data | Experiences from real users | Evaluating actual UX |
| Lab Data | Controlled performance simulation | Diagnosing problems |
PageSpeed Insights reports field data from CrUX when enough information is available. Google evaluates Core Web Vitals using the 75th percentile of user experiences, which means the target is to provide good performance for the majority of visitors rather than only under ideal conditions.
GTmetrix vs. PageSpeed Insights
You do not need to choose only one tool. They work best together.
| Feature | GTmetrix | PageSpeed Insights |
|---|---|---|
| Quick performance overview | Excellent | Excellent |
| Lighthouse analysis | Yes | Yes |
| Core Web Vitals | Yes | Yes |
| CrUX real-user data | Available where eligible | Available where eligible |
| Waterfall analysis | Strong | Limited |
| Resource-by-resource debugging | Excellent | Moderate |
| Google-focused performance analysis | Useful | Best choice |
| Mobile/desktop analysis | Available | Built into standard workflow |
What Should You Fix First?
Do not work through every recommendation from top to bottom. Prioritize problems that directly affect users.
If LCP is poor, start with the main content element, hosting response, image optimization, caching, and critical resources. If CLS is poor, inspect images, ads, banners, fonts, and dynamically inserted elements. For poor INP, investigate unnecessary JavaScript, third-party scripts, plugins, and long browser tasks.
Test Again After Optimization
Performance optimization requires comparison. Record your original results, make meaningful changes, and run the same pages through GTmetrix and PageSpeed Insights again.
Use consistent testing conditions whenever possible. Also test more than one URL because a fast homepage does not guarantee that a complex landing page or blog article performs equally well.
Website Speed Is About Users, Not Just Scores
A fast website should load important content quickly, respond immediately to user actions, remain visually stable, and perform well across real devices and connections.
Start with GTmetrix to uncover obvious loading problems, but make Google PageSpeed Insights and Core Web Vitals your main performance reference. Before spending more money on SEO campaigns or paid advertising, make sure visitors can actually reach and use your website without unnecessary delays.
If your PageSpeed results reveal persistent performance problems, explore Dune Seed’s website optimization and technical SEO resources to identify the changes that can improve both user experience and organic growth.
Frequently asked Questions
Is GTmetrix or PageSpeed Insights better?
They serve slightly different purposes. PageSpeed Insights is the better primary reference for Google's performance metrics and Core Web Vitals, while GTmetrix provides excellent diagnostic information such as Waterfall analysis, resource loading order, requests, and page composition. Using both gives you a more complete understanding of website performance.
What is a good Google PageSpeed Insights score?
A Lighthouse Performance score of 90 or higher is generally considered strong, but the score should not be your only target. Core Web Vitals and real-user experience are more important than chasing 100. Focus on whether visitors can load, view, and interact with important page content quickly.
Why does GTmetrix show a different score from PageSpeed Insights?
The tools may use different test environments, locations, network settings, devices, and testing configurations. Even repeated tests with the same tool can vary slightly. Compare patterns and major performance issues rather than expecting identical scores across different testing platforms.
What are the three Core Web Vitals?
The current Core Web Vitals are Largest Contentful Paint, Interaction to Next Paint, and Cumulative Layout Shift. Google recommends an LCP of 2.5 seconds or less, INP of 200 milliseconds or less, and CLS of 0.1 or less.
Does website speed affect SEO?
Website performance contributes to overall page experience, and Google recommends achieving good Core Web Vitals. However, speed is only one part of search performance. Relevant content, search intent, technical accessibility, backlinks, and many other signals also influence organic visibility.
Why is my mobile PageSpeed score lower than desktop?
Mobile testing represents more constrained hardware and network conditions. Large images, JavaScript, plugins, tracking scripts, and complex page layouts therefore have a greater impact. This is why mobile optimization should receive particular attention when improving website performance.
How often should website speed be tested?
Test important pages after major design changes, plugin installations, hosting changes, advertising-script additions, tracking updates, or large content changes. Active commercial websites should also monitor performance periodically because small additions can gradually make pages slower.