Google rates every page on three metrics that measure how a website actually feels: how fast the content appears, how quickly it responds to a tap, and whether it jumps around under your finger. They are called Core Web Vitals, and they affect both rankings and sales. Here is how to fix them in practice, with real numbers from a website we have just optimized.
The three metrics in plain language
LCP (Largest Contentful Paint) - how long it takes for the largest element on the screen to appear: the hero image or the main heading. Target: under 2.5 seconds. This is the metric most often in the red zone on Bulgarian websites.
INP (Interaction to Next Paint) - how long the page takes to respond when you tap a button or open a menu. Target: under 200 milliseconds. Heavy JavaScript is the usual culprit.
CLS (Cumulative Layout Shift) - how much the content “jumps” while loading. Everyone has seen text jump away just as they were reading it, because an ad loaded above it. Target: under 0.1.
A real case: from 6.4 to 3.4 seconds
A fresh optimization from our own work. The homepage of one website measured LCP 6.4 seconds on mobile, deep in the red zone. The diagnosis took longer than the fix itself:
The large image in the hero section was set as a CSS background (background-image). The difference is fundamental: the browser sees regular <img> tags as soon as it reads the HTML and starts downloading them, while CSS backgrounds are only discovered after all the styles have been processed, which means seconds of delay. On top of that, phones were served the same 129 KB image made for a wide monitor.
Two changes: a high-priority preload so the download starts right away, and a separate 30 KB mobile version. The result: LCP of 3.4 seconds, and the load time of the image itself dropped from 5.9 to 1.7 seconds. Without changing a single line of the design.
What fixes LCP
The right format
WebP instead of PNG/JPG cuts the file size in half at the same quality. Never serve a 2000px-wide image to a phone.
Preload the hero image
A single <link rel="preload"> with fetchpriority="high" for the first large image often cuts seconds in one go.
Fast server and caching
If the server takes 600ms to respond, you start half a second behind. Static caching and the right choice of hosting solve this.
Typefaces
font-display: swap and only the weights you need. Five fonts in four weights each add up to a megabyte nobody ordered.
What fixes INP and CLS
For INP: remove the plugins you don't use (each one loads its own JavaScript), defer third-party scripts such as chats, pop-ups and trackers, and be careful with animation libraries. A website rarely needs three at once.
For CLS the recipe is short: set width and height on every image, reserve space for ads and banners before they load, and never insert content above what someone is already reading.
Speed is not technical vanity. Every extra second of loading time noticeably lowers conversions - for an online store, that is revenue lost directly, every day (ask us and we will calculate how much).
What to measure with
Ask us for a free SEO check - for a quick overview, including server response time and compression. PageSpeed Insights (pagespeed.web.dev) - the fastest check; it also shows real user data if the site has enough traffic. Search Console → Core Web Vitals - shows your whole set of pages and which groups are in the red. Lighthouse in the browser - for detailed diagnostics during development. Always measure the mobile version: that is the one Google rates you on.
When fixes are not enough
Sometimes the problem is not in the settings but in the foundation: a website weighed down by a heavy page builder, 40 plugins and a theme bought for 40 dollars six years ago. In cases like that, optimization is like putting new tires on a car with a broken engine - it makes more sense to invest in a new website (when exactly it is time) with a clean foundation than to keep patching up the old one forever. If the website is good but neglected, regular maintenance keeps it fast, instead of you fixing it once every two years.
Conclusion
Core Web Vitals are no mystery: they are three numbers with clear targets and well-known remedies. LCP under 2.5s, INP under 200ms, CLS under 0.1. Start by measuring the mobile version, tackle the largest image and the server response, and in most cases you will gain seconds with a few hours of work.
Not sure where your bottleneck is? Write to us: we will measure your website and tell you exactly which three things to fix first and what you will gain from them.
