Images that are too heavy
Photos loaded at full resolution are the number one cause. They need resizing and modern formats like WebP.
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Why your website is slow (and what it costs you)
Speed isn't a technical detail: it's the first impression and a ranking factor. Here's what slows a site down and how much it's costing you.
In short
A website is slow mainly because of heavy images, too many plugins and scripts, poor hosting and unoptimised code. It matters because speed is a Google ranking factor (Core Web Vitals) and affects conversions: past 3 seconds of load time you lose most of your visitors. The good news: it can almost always be measured and fixed.
Gian Luca Partengo
Web developer since 1995 · bespoke websites · Updated:
A slow site loses visitors before it even shows them what you offer. People don't wait: if a page doesn't appear in a few seconds, they go back and click on your competitor.
Speed is also SEO: Google uses the Core Web Vitals as a ranking signal. A fast site reads better, converts more and costs less in advertising.
53%leave a mobile page that takes over 3 seconds to load
1sof delay can be enough to lose a conversion
0,1severy tenth of a second weighs on sales and SEO
What actually slows a site down?
Almost always, slowness comes from a handful of recurring causes.
Too many plugins and scripts
Every plugin adds code, requests and points of failure. On a CMS they pile up by the dozen without you noticing.
Bloated code
Generic themes load styles and features you never use. The browser still has to download and process them all.
No caching
Without caching, the server rebuilds every page from scratch on each visit, wasting precious time.
Inadequate hosting
Cheap, overcrowded hosting responds slowly: it's the foundation everything else rests on.
External resources
Fonts, widgets, trackers and maps loaded from third parties block rendering and slow the page down.
Core Web Vitals: which numbers does Google look at?
Three metrics measure the real experience. These are the values to hit.
LCP — loading
Largest Contentful Paint: when the main content appears. Target: under 2.5 seconds.
INP — responsiveness
Interaction to Next Paint: how ready the site is when you interact with it. Target: under 200 ms.
CLS — stability
Cumulative Layout Shift: how much the layout «jumps» while loading. Target: under 0.1.
How do you speed up a site you already have?
You don't always need to start over. If the site isn't bloated at its core, these steps deliver real results quickly.
1. Lighten your images
The first and most effective step: resize photos to their real display size and convert them to WebP. On its own this often halves page weight.
2. Turn on caching
Server and browser caching avoid rebuilding and re-downloading everything on each visit. On a serious host it's a few clicks away.
3. Remove useless plugins
Every plugin you don't use is dead weight and risk. Disable and delete anything non-essential: less code, faster site.
4. Defer scripts and fonts
Load JavaScript deferred and fonts without blocking text. Drop third-party widgets and trackers you don't really need.
5. Switch hosting if needed
If the server responds slowly, no optimisation is enough. <a href="/en/guides/choosing-hosting/">Adequate hosting</a> is the base for everything else.
6. Measure, fix, measure again
Start from PageSpeed Insights, apply one change at a time and check the effect. Optimising at random does more harm than good.
How do you measure a website's speed (for free)?
Before you touch anything, measure. These three tools are free, reliable and used by professionals.
PageSpeed Insights
Google's tool: it gives you real-user Core Web Vitals and a 0–100 score with targeted advice.
Lighthouse
Built into Chrome (DevTools): it analyses performance, accessibility, best practices and SEO. It's the test I run on every site before and after launch.
WebPageTest
WebPageTest shows loading frame by frame from different locations and devices: ideal for understanding what blocks the page.
What does slowness cost you?
Slowness isn't a cosmetic problem: it's a cost. Every extra second drives visitors away, lowers conversions and makes you pay more for advertising.
A fast site flips it all around: more people stay, more leads come in and Google rewards you. It's the difference between a site that's built well and one that's improvised.
A lot of slowness comes down to hosting. How to choose the right hosting.
Slow vs fast site
LCP (loading)
Slow4,5 s
Fast1,2 s
Page weight
Slow~3 MB
Fast~0,4 MB
Bounce rate
Slow~50%
Fast~20%
Indicative values: they vary from project to project, but the direction is always this.
How do I build genuinely fast sites?
Speed isn't added later: it's designed in from the start.
Hand-written, lightweight code
I write only the code that's needed. No generic themes, no features nobody will use.
Optimised images
Every image is resized, compressed and served in WebP, with lazy loading.
Zero plugins
No plugins to load, update or slow things down: features are written to measure.
Minimal CSS and JS
Styles and scripts cut to the essentials and minified, so the browser has little to process.
Caching and hosting done right
Caching set up properly and hosting matched to the project: the base that holds everything.
I always measure
Every site is checked with Google Lighthouse before and after launch. No promises, numbers.
What results can I prove?
Every project I deliver is measured with Google Lighthouse on mobile. These scores aren't lucky: they're the result of how the site is built.
Google Lighthouse · mobile · mobile
Google Lighthouse scores (mobile) for this very site, verifiable on Google PageSpeed.
Frequently asked questions about speed
Common doubts about performance, Core Web Vitals and SEO.
How do I know if my site is slow?
You can measure it for free with Google PageSpeed Insights or Lighthouse: they give you the Core Web Vitals and a score from 0 to 100. Below 50 on mobile, the site is definitely slow.
Why is my WordPress site slow?
Usually because of accumulated plugins, heavy themes and unoptimised images, on top of shared hosting. The more elements there are, the more the browser has to download and process.
Does speed really matter for SEO?
Yes. Google uses the Core Web Vitals as a ranking factor, and fast sites get more visits and fewer bounces. With equal content, the faster one wins.
Is a cache plugin enough to speed things up?
It helps, but it's a band-aid. If the problem is bloated code, too many plugins or heavy images, caching only masks it in part. Real speed comes from how the site is built.
How fast should a site load?
Aim to show the main content (LCP) within 2.5 seconds on mobile, with a light page weight. A well-built site loads in just over a second.
Does GLP speed up an existing site or rebuild it?
GLP does not modify existing code: I build new websites or complete rebuilds. If the current site is slow, the audit defines the content, URLs and scope for reconstruction.
Does a CDN really speed up a site?
It helps, especially if you have visitors far from your server: it spreads resources across nodes near the user. But it's an accelerator, not a cure: if the site is heavy or badly built, a CDN moves the problem rather than solving it.
Do WebP images really make a difference?
Yes, a big one. WebP (or AVIF) is on average 25–35% lighter than JPEG and PNG at the same quality. On photo-heavy pages it's often the single change with the biggest impact on speed.
Next step
Is your site too slow?
Run a free first check of visible technical signals: mobile performance, indicative page weight, WordPress footprint and security headers.