Web performance: why it’s so important and how to optimize it

No one is surprised by a page that loads quickly, but a page that loads slowly is too noticeable and you will quickly want to leave it before the content even shows up on the screen. In fact, most visitors will leave a website if the page doesn’t fully load in less than 3 seconds.

In the highly competitive e-commerce sector where speed is of the essence, ensuring good web performance is essential to converting your visitors into customers, both on mobile and desktop. It is estimated that a 0.1-second improvement in the load time of your eCommerce site can increase your conversion rate by 8%!

Why is it essential to improve the performance of your online store?

  • You will significantly improve your customer experience and naturally increase your conversion rate,
  • You will gain the capacity to accommodate the maximum number of users at the same time and avoid losing valuable customers during busy periods,
  • You will gain visibility thanks to the optimal loading speed of your site, which will allow you to improve your position in search engine results (SEO).

So when you think about the presentation of your online store, you should think about user experience, conversion, and visibility.

What metrics are important and how to optimize them?

When it comes to your store, the most important thing is to improve the loading speed while meeting the technical requirements of an e-commerce site in 2022.

Time To First Byte and Speed ​​Index is considered particularly important metrics as they give a good overview of website performance.

1. Time to First Byte (TTFB)

This metric corresponds to the response time of the server. Some of the main elements that make up response time are server configuration (languages, libraries, etc. that optimize load times and make the website robust) and database query execution times.

If this indicator is less than or equal to 200 milliseconds and acceptable up to 500 ms Google considers this as good. It is often the only indicator that varies over time and is often driven by traffic.

Tip: Use a CDN (Content Delivery Network) which will be especially useful for your overseas customers.

2. The First Contentful Paint

On the user side, this is the main focus. Visitors may find themselves with a waiting time between the time they click a link and the time the page displays an element. This measure basically corresponds to the time it takes the browser to load the response from the server and display the first element of content from the browser.

Good to know: It qualifies as good if it’s done in less than 2.5 seconds (including TTFB), so we can estimate that the load time for the render-blocking files should be less than 2 seconds.

To do this you can compress your HTML/CSS/JS files and limit files that block the display.

3. The Largest Contentful Paint (LCP)

LCP is the second highlight for the user, this measure integrates most of the visible elements. This is when the web page takes shape and takes on its final – or almost final – look. This step can be the longest and most difficult depending on the content to be displayed.

Good to know: It is considered good if achieved in less than 2.5 seconds (like FCP) and up to 4 seconds is acceptable. Many studies show that after 3 seconds the bounce rate increases significantly

Tip: Optimize images, generate useful formats (jpeg 2000, jpeg XR webp, etc.), provide different sizes of your images in the HTML code, and set cache (browser and server).

4. The First Input Delay

This indicator is related to the interactive aspects of the page. Simply put, it’s the browser’s response time between an action being taken (for example, a link or button being clicked) and the moment the first interactive element appears.

Good to know: This indicator measures the user’s “disturbance time”, i.e. the amount of time the user will wait for the browser to respond if they click on the first displayed interactive element.

5. Time to Interactive

This indicator is often misinterpreted. It measures the time from the start of the navigation until the page resources are loaded and the main browser thread is idle for at least 5 seconds, i.e. there has been no script execution longer than 50ms.

Good to know: Your e-commerce site can have good overall performance, good FID, and poor interactivity time.

Tip: Defer non-essential JavaScript code to load and delete unnecessary page rendering scripts to clear up the main thread. This requires you to do good code segmentation.

Here is a more representative timeline of the lag between indicators – and the timeline of a good site (according to Google)

Bonus Indicator: Speed ​​Index or SI This indicator is a bonus because it is very dependent on FCP and LCP, which are themselves dependent on TTFB. This is the result of a calculation based on the speed and progressivity of the visible parts of the page (floating blocks).


Each indicator is influenced by the previous one, which makes them important. With PosFox, you get a cheap online store and a well-optimized one.