Why website speed matters and how to measure it

Visitors decide quickly. If a page takes a long time to load, they leave before they even see what you offer. Speed also affects how Google shows you. The good news is that most speed problems can be measured precisely and fixed in a targeted way.

What are Core Web Vitals

Google evaluates the user experience through three metrics:

• LCP (Largest Contentful Paint) – how long it takes for the largest element on the page to appear, typically the main image or heading. The target is under 2.5 seconds.
• INP (Interaction to Next Paint) – how quickly the page responds to a click or typing. The target is under 200 ms.
• CLS (Cumulative Layout Shift) – whether the content “jumps” while loading. The target is below 0.1.

How to test your speed

The simplest tool is Google’s PageSpeed Insights. Enter the address and you get a score for mobile and desktop, the Core Web Vitals values and a list of recommendations. Focus mainly on the mobile results, because most visitors come from phones and mobile tests simulate a weaker device and a slower connection.

If the website has enough traffic, PageSpeed also shows real user data. That is more valuable than a lab test, because it shows how the website really performs for your customers.

The most common causes of a slow website

• Large images. A photo straight from a camera can be several megabytes. The right format (WebP, AVIF) and size often save more than everything else combined.
• Too many scripts. Chats, analytics, sliders and plugins that load their files everywhere.
• No cache. Without it, the server builds the page from scratch on every visit.
• Weak hosting. The cheapest shared hosting may not be enough for an e-shop with thousands of products.
• A heavy theme or page builder. Universal themes carry a lot of code your website never uses.

Changes with the biggest effect

In practice the work goes from the cheapest steps to the more demanding ones: optimising and lazy-loading images, turning on caching and compression, removing unused plugins and scripts, and deferring things that aren’t needed right away. Only then does it make sense to consider changing the hosting or reworking the theme.

Summary

Speed isn’t cosmetic. It is part of the user experience and affects both sales and SEO. Measure, fix the biggest problems first and repeat the measurement after every major change. If you want to know where your website is losing time, a review gives you a concrete list of improvements.