Is your site as fast as your visitors expect? It’s a simple question, but the answer can impact your entire online business. A few seconds’ latency on an e-commerce site is enough to lose many sales. So site speed isn’t a luxury: it’s a necessity.
In this article, we’ll take a step-by-step look at how site speed is measured and built. You’ll understand why your site’s performance is so decisive, how to measure it effectively, and above all, how to optimize it to offer your visitors a smooth browsing experience. Whether you’re an entrepreneur, a project developer or already running an online store, you’ll find all the information you need to build a high-performance site.
Why is site speed crucial?
Impact on user experience
Every second counts. You know it, and so do your visitors. A page that takes more than three seconds to load often means a visitor abandons his or her shopping cart. According to a Google study, 53% of mobile users leave a site if it takes more than 3 seconds to load.
Have you ever wondered how many sales you lose because of this? Optimizing loading speed means improving the user experience, and therefore your conversions.
Impact on search engine optimization (SEO)
Site speed is a ranking criterion for search engines. This doesn’t mean that performance is the only thing that counts, but a slow site will automatically be penalized, especially since the introduction of Core Web Vitals. There are three major indicators that must be taken into account:
- LCP (Largest Contentful Paint): measures the display time of the main content.
- FID (First Input Delay): measures the delay between the first user interaction and the site response.
- CLS (Cumulative Layout Shift): measures visual stability.
If your site is failing on these metrics, it’s time to take action.
Effects on conversions and sales
Amazon found that a slowdown of 100 milliseconds resulted in a 1% drop in sales. Imagine what this means for your e-shop.
It’s no coincidence. Performance is money.
How do you test your site’s speed?
Free, high-performance tools
I recommend these essential tools. They are free and very complete:
- Google PageSpeed Insights: this tool analyzes both the mobile and desktop versions of your site. It provides detailed recommendations with a score out of 100.
- GTmetrix: very useful for obtaining a complete diagnostic: waterfall, loading time, file size… It also lets you test in several countries.
- WebPageTest : one of the most accurate on the market. It lets you simulate a real connection, choose a browser and a country.
Pingdom Tools: simple, fast, effective. Ideal for an initial analysis. - LoadFocus: more oriented towards load testing, but useful if you have a lot of traffic.
Test methodology
Here are my tips for effective analysis:
- Test several times, at different times of the day.
- Use different devices: smartphone, tablet, PC.
- Choose relevant geographic locations (if your audience is international).
- Analyze both versions: mobile and desktop.
This will give you a realistic view of your site’s performance.
Interpreting test results
Understanding key metrics
These indicators are essential:
- LCP (Largest Contentful Paint): ideally, less than 2.5 seconds.
- FID (First Input Delay): must remain below 100 ms.
- CLS (Cumulative Layout Shift): must be less than 0.1.
Other indicators such as Time to First Byte (TTFB) or Total Blocking Time (TBT) can also alert you to server-side problems or scripts that are too heavy.
Identify areas for improvement
The tools list opportunities for improvement that you can then implement:
- Images too heavy: convert them to WebP format.
- JavaScript scripts that block rendering: load them asynchronously.
- Large style sheets: make them smaller.
By analyzing the loading cascade, bottlenecks can be identified.
Optimize your site’s speed
General techniques
Here are the actions I recommend:
- GZIP or Brotli compression: activate it on your server, and the amount of data exchanged over the network will be considerably reduced.
- CSS/JS/HTML minimization: tools such as UglifyJS or CSSNano are highly effective.
- Lazy loading: load images only when they become visible.
- Browser cache: define long-lasting caching rules.
- Using a CDN: such as Cloudflare, KeyCDN or Bunny.net.
Prestashop features
Prestashop offers many optimization levers:
- Activate CCC (Combine, Compress, Cache): in advanced settings.
- Disable unused modules: they slow down the front office unnecessarily.
- Clean up databases: log tables, expired connections, etc.
- Optimize product images: generate thumbnails adapted to each device.
- Choose an optimized theme: some themes are overloaded with scripts and CSS.
Modules such as “Page Cache Ultimate” or “Image Optimizer” can save several seconds.
Tips for maintaining good performance over time
Implement continuous monitoring
For example, I recommend using the following tools:
- Google Search Console: for tracking mobile/desktop performance.
- New Relic or Datadog: for continuous server-side analysis.
- Monitoring via GTmetrix Pro: to be alerted to score decreases.
Plan regular audits. Perform them before and after each major update.
Good development practices
Respecting a certain number of good development practices is necessary to obtain a reliable, stable, maintainable and scalable site:
- Respect a clean code architecture: this will make it easier to find your way around the code.
- Document modifications: keeping a record of every action on the site makes it easier to find improvements or analyze anomalies.
- Avoid “quick fixes” with no long-term impact: a quick fix, without impact analysis, is often much more expensive than a well-thought-out fix.
- Test your modifications on a dedicated environment: using a copy of the site in an environment as similar as possible to your production environment will enable you to test the modifications you have made in conditions close to reality;
The quality of your code has a direct impact on performance.
To conclude on site speed testing
Testing and optimizing site speed is not an option. It’s a fundamental pillar of any successful digital strategy. As a specialist Prestashop developer, I can tell you: a fast site is a site that sells.
You now have all the keys you need to measure, analyze and improve the performance of your online store. But if you’d like me to provide you with more personalized support, I can. Every site has its own specificities, and successful optimization requires a tailor-made analysis.
Contact me to discuss your project.
