The short verdict
- Most generated marketing sites are slow for the same five reasons.
- Images and JavaScript account for most of the weight. Fix those first.
- Measure on a mid-range phone, not on your laptop over office wifi.
01Why generated sites tend to be heavy
Several popular builders produce single-page apps: a JavaScript bundle that runs in the browser and then draws the page. That approach is great for apps with logins and dashboards. For a five-page marketing site, it means the visitor downloads and runs code before they see a headline that could have been plain HTML.
Add full-size images, three font families and an animation library, and a page that looks simple can weigh several megabytes.
02The five causes, ranked
1. Images that are far too big
A 4000-pixel photo shown in a 600-pixel card. A PNG where a WebP or AVIF would be a fifth of the size. No lazy loading, so images at the bottom of the page download before the visitor scrolls. On many generated sites, images are the largest single share of page weight, and the easiest to fix.
2. JavaScript before content
If the page is drawn by JavaScript, nothing useful appears until the bundle has downloaded, parsed and run. On a mid-range Android phone that can take seconds. Pre-rendering the pages as HTML, or rebuilding them on a platform that serves HTML, removes the wait.
3. The hero image or video
The largest thing in the first screen decides your Largest Contentful Paint, one of Google’s Core Web Vitals. If it is a 3MB background video or an image loaded late by script, the whole page feels slow even if everything else is fine.
4. Fonts
Each family and each weight is a separate download. Four weights of two families is eight files. Self-hosting, subsetting and using font-display: swap stop fonts blocking the text.
5. Third-party embeds
Chat widgets, video players, booking tools, tracking scripts. Each one brings its own JavaScript, and you do not control how heavy it is. Load them after the page, or only when someone clicks.
03What good looks like
Google’s Core Web Vitals give you three targets, measured on real visitors:
- Largest Contentful Paint under 2.5 seconds. How fast the main content appears.
- Interaction to Next Paint under 200 milliseconds. How fast the page responds to a tap.
- Cumulative Layout Shift under 0.1. How much the page jumps around while loading.
“A fast site is mostly a list of things you decided not to load.”
04Where to start
Run PageSpeed Insights on your homepage and your most important landing page, and choose the mobile result. Look at the “Opportunities” list. If images and JavaScript are at the top, you are in the usual situation, and the order above is the order to fix things in.
If the main problem is that the page is drawn by JavaScript, there is a limit to how fast it can get without changing how it is built. That is one of the clearer signs that a move, rather than a tune-up, is worth considering.
05Questions people ask
My Lighthouse score is fine on desktop. Is that enough?
No. Desktop tests run on a fast machine. The mobile test simulates a mid-range phone on a slower connection, which is closer to what many visitors have.
Does speed affect SEO?
Core Web Vitals are part of Google’s ranking signals, but a small one compared with relevance. The bigger effect is on people: slow pages lose visitors before they read anything.
Will a faster host fix it?
Rarely on its own. Most of the delay happens in the browser, downloading and running what the page asks for.
Can you tell me what is slowing my site down?
Yes. Send us the link and we will tell you the top two or three causes and whether they can be fixed in place.
