Why does website speed matter?

Nowadays, the speed of websites is playing an even bigger role, es­pe­cial­ly thanks to mobile devices. As tech­nol­o­gy and con­nec­tiv­i­ty evolve, so do user re­quire­ments. There are hardly any options these days - websites need to be fast.

Mobile users

Browsing websites on mobile devices is very common today, and the number of mobile users is constantly growing. It is therefore extremely important to also take mobile users into account when creating websites.

About half of mobile users stop loading websites after 3 seconds, meaning that the bounce rate on a slow website can be huge. According to Google, a mobile user also leaves a website 5 times easier if the website lacks mobile optimization.

So websites today need to be both fast and mobile friendly. In practice, modern websites must load in less than 2 seconds and run on different devices, so these must also be responsive.

What things affect website speed?

Website speed is affected by the platform, servers, CSS and JavaScript files, images, and cache. It all starts with a platform (e.g. Wordpress or a website builder) and the right choice can save you a lot of work.

Here are 5 important and note­wor­thy things about website speed. The list could be longer, but it’s good to start with these.

Static or dynamic websites?

The server does sig­nif­i­cant­ly less work when it comes to static websites, and these are usually nice and fast to browse. Static websites also tend to withstand visitor spikes better than dynamic websites, meaning there may be more con­cur­rent visitors.

Dynamic websites (such as those made with Wordpress) consume more server resources, and therefore load more slowly. In addition, dynamic websites must take security into account.

If there is no par­tic­u­lar need for a dynamic website, you should implement the website as static.

Servers and their location

A slow server on the other side of the world can sig­nif­i­cant­ly slow down websites. It is important that the server responds quickly, and is located at least fairly close to the user.

It is a good idea to serve static files through a Content Dis­tri­b­u­tion Network (CDN), which is designed to dis­trib­ute files to users up close and fast.

External scripts

Sometimes it is necessary to add for example a chat box or an external booking system to your site. These should be added carefully, as these may affect the speed of your website.


Images with large file sizes easily slow down pages, es­pe­cial­ly on slow con­nec­tions. The sleek user ex­pe­ri­ence is achieved with optimized images that are not too much on one page.

Browser cache

It is a good idea to leverage the user's browser cache. In practice, the user does not always have to reload files from the server if these are already found in their browser's cache. This saves bandwidth and speeds up loading times.

Search engines

Search engine optimization today needs to take into account website speed, as Google in particular values  fast sites. Google has reported in 2010 that website speed is a ranking factor. At the time, it was computer users. In 2018, this was announced for mobile searches as well.

Tests based on Google's user experience (Core Web Vitals) will be a ranking factor in May 2021. More on these below.

Website speed testing (Google PageSpeed Insights)

Per­for­mance can be measured, for example, with Google's PageSpeed Insights test, which gives points to the websites you test. Tests are performed on both the computer and mobile versions of the website.

You can easily take the test at https://de­vel­op­ and start the test by filling in the website address field and clicking the Analyze button. When the test is complete, the scores, times and problem areas / sug­ges­tions for im­prove­ment are displayed.

In addition to lab data, some sites show field data that has been collected anony­mous­ly from real users. If Google does not have enough in­for­ma­tion, the field data will not be displayed. In practice, the field data comes from real users, and the lab­o­ra­to­ry data is Google's own sim­u­la­tion. There are dif­fer­ences in the results of the two, due to e.g. that the real users have different devices and con­nec­tions.

According to Google, a good result is 90+ points, 50-89 means that the page requires op­ti­miza­tion, and less than 50 points is bad. 100 points is quite difficult to get when the pages need to have content and you usually also want the site to look good. In practice, 90+ points is already an excellent result.

Core Web Vitals


The LCP, FID, and CLS shown in the test are related to Google’s Core Web Vitals metrics, which measure the user ex­pe­ri­ence of pages.

Largest Con­tent­ful Paint (LCP)

The time in seconds before the user sees the largest content element on the page. Less than 2.5 seconds is con­sid­ered good for the user ex­pe­ri­ence.

First Input Delay (FID)

This measures user in­ter­ac­tiv­i­ty (e.g. when a user clicks on a button on a page). This value should be less than 100 mil­lisec­onds.

Cu­mu­la­tive Layout Shift (CLS)

The visual stability of the page, that is, whether the elements change position on the page during loading. The value should be less than 0.1. The higher the value, the more elements move on the page during loading, which is bad for the user ex­pe­ri­ence.


First Con­tent­ful Paint (FCP)

The time in seconds before the user sees the first part of the page.

Speed Index

Indicates how quickly the content of the page appears. More than 5.8 seconds is slow, 4.4-5.8 seconds is moderate and 0-4.3 seconds is fast.

Time to In­ter­ac­tive

The time before the page is fully in­ter­ac­tive, after which all functions on the page are available.

Total Blocking Time

A time that prevents in­ter­ac­tiv­i­ty when a user cannot access functions on a page.

Fast static websites with Oidom

Websites created with Oidom are published statically to servers around the world. This way they always load quickly and the server is always as close to the user as possible. Oidom automatically optimizes sites and images, and the user is not required to take any special measures to optimize. The pages also work directly on mobile devices, and of course quickly. Speed is one of Oidom's most important features.