A slow website rarely has just one cause. Common problems include oversized images, heavy videos, too much JavaScript, external tracking tools, fonts and slow server responses. Start with measurements rather than guesses.
Google uses Core Web Vitals to assess real user experience in loading, responsiveness and visual stability.
1. Images are too large
This is one of the easiest problems to understand.
If a page loads a photograph several megabytes in size but displays it as a small card image, the visitor still has to download the unnecessarily large file.
Possible fixes include:
- dimensions suited to the image's use
- a modern file format
- sensible compression
- responsive image versions
- lazy loading for images further down the page
However, do not delay the hero image incorrectly if it is the largest visible element on the page.
2. A heavy video loads at the top
An automatically loaded background video can look good on a fast connection but significantly delay the first view of the page.
If the video is not essential to the message, a lightweight image or more controlled video loading may work better.
3. There is more JavaScript than the page needs
Every additional library, animation, widget and tracking script can add work for the browser.
JavaScript itself is not the problem. The problem is unnecessary work that must finish before the visitor can use the page smoothly.
4. Third-party tools slow things down
Chat tools, booking systems, maps, videos, analytics, advertising pixels and other external services can add network requests and JavaScript.
Ask this about each tool:
Does it provide enough benefit to the customer or business to justify its loading cost?
5. Too many fonts are loading
Several font families and many weights can increase downloads and cause text to change as the page opens.
One or two well-chosen fonts are often enough.
6. The server responds slowly
If the server or backend takes a long time to start responding, the browser must wait before it can even begin building the page.
Static or well-cached content can be very fast because the server does not have to build the page from scratch for each request.
7. The top of the page takes too much work to render
A page feels slow when its largest visible element appears late, even if other things are happening quickly in the background.
This often shows up in LCP (Largest Contentful Paint), which measures how quickly the largest visible content element is drawn on screen.
8. The layout jumps while loading
If space is not reserved for an image or embed, other content can move when it loads.
This is frustrating and can cause accidental taps. Google's CLS (Cumulative Layout Shift) metric tracks this kind of unexpected visual movement.
What do Core Web Vitals numbers mean?
Google recommends these targets for a good user experience:
- LCP (Largest Contentful Paint): no more than 2.5 seconds; how quickly the main content becomes visible
- INP (Interaction to Next Paint): less than 200 milliseconds; how quickly the page responds to an interaction
- CLS (Cumulative Layout Shift): less than 0.1; how stable the layout stays while loading
Use real user data to assess these where enough data is available.
PageSpeed Insights also provides lab measurements to help identify individual problems.
What do PageSpeed scores tell you?
PageSpeed Insights is a free Google tool for assessing a web page's speed. Its performance score rates how the page did in loading and readiness measurements on a scale of 0-100. Scores of 90-100 are in the tool's good range.
In practice, speed means your service description appears promptly and customers do not have to wait before they can use the page.
Why are mobile and desktop scores different?
The tool tests mobile and desktop separately. The mobile test simulates a slower device and connection, so the same page can receive a lower score.
When comparing results, always check whether they are mobile or desktop scores and when they were measured.
Why can the score change?
Server load, external services and test conditions can vary. The same page can therefore receive slightly different scores between runs.
One measurement reflects one test run. PageSpeed test scores are also different from Core Web Vitals data collected from real visitors.
Does a score of 100 mean the website is good?
A good score describes performance in that test. It does not tell you whether prices are easy to find, the copy is clear or the contact form works.
A perfect score does not guarantee a high Google ranking either. Useful content and a website that works well as a whole also matter.
Do you need a PageSpeed score of 100?
No.
Google itself notes that chasing a perfect score purely for SEO (Search Engine Optimization) may not be the best use of your time. The overall experience matters more.
If the site is quick to use, important content appears promptly and getting in touch is straightforward, you are on the right track.
Where should you start?
Work in this order:
- Measure your most important pages.
- Check the largest images and videos.
- Remove unnecessary external scripts.
- Check how the main content at the top loads.
- Reserve space for images and embeds.
- Check the fonts.
- Investigate server or hosting delays if they are significant.
- Test on a phone using an ordinary mobile connection.
How does GC account for speed?
GC's website service includes image optimisation, hosting, HTTPS (Hypertext Transfer Protocol Secure), an encrypted web connection, and ongoing technical care. Sites are built to work on phones, tablets and computers. We aim for a 100/100 performance score in Google PageSpeed Insights on every page.
Speed does not come from one trick. Keep the site as lightweight as possible from the start rather than trying to fix an overly heavy design at the end.
See also what makes a website mobile-friendly.
Sources: Lighthouse performance scoring. Google Search Central, Understanding Core Web Vitals and Google Search Results and Understanding Page Experience in Google Search Results.