Your visitors never see your servers or scripts, only a blank screen that won't finish loading. Every extra second gives them a reason to close the tab and return to the search results, and Google takes speed into account when ranking pages. The good news is that the causes of a slow site are well known, easy to measure and usually fixable without a rebuild.
In short
- Speed affects whether people wait for your page, whether they send an enquiry and how high your site ranks in Google.
- The usual culprits are heavy images, too much JavaScript, third-party widgets, embedded videos and slow hosting.
- Most problems are solved with modern image formats, lazy loading, a CDN, caching and fewer unnecessary scripts.
Why speed is a sales issue
The path to a purchase has several steps: open the page, find the product, add it to the basket, check out. A slow site adds a pause to each one, and at every pause some people leave. They don't complain; their enquiries simply never arrive.
Mobile visitors feel this most. A weaker processor and patchy mobile internet can make a site that opens quickly on an office computer noticeably slower on a smartphone.
There is a less visible effect too: trust. A page that keeps "thinking", jumps around while loading or ignores taps looks unreliable, and someone deciding whether to trust you with their card details notices that straight away.
How Google measures speed: Core Web Vitals
Google measures visitor experience with three metrics called Core Web Vitals and uses them among its ranking signals. Here they are, with the thresholds Google describes as good:
- LCP (Largest Contentful Paint): how quickly the largest visible element on the first screen appears, usually the main image or headline. Good means 2.5 seconds or less.
- INP (Interaction to Next Paint): how quickly the page responds to a tap, a keystroke or opening a menu. Good means 200 milliseconds or less.
- CLS (Cumulative Layout Shift): how much the content jumps around while loading, like a button that moves just as you tap it. Good means 0.1 or less.
Google relies on data from real visitors: a metric counts as good when the threshold is met for at least 75% of visits. Speed won't replace useful content, but when many pages are similarly helpful, a better experience can give yours the advantage.
What usually slows a website down
Images come first almost every time. A camera or stock photo goes onto the site as it is, several megabytes in size, though it fills a few hundred pixels on screen. The phone ends up processing far more data than it needs.
Next comes JavaScript. Sites often pull in large libraries for a single animation or slider. While the browser downloads and runs that code, the page doesn't respond to the visitor, which directly hurts INP.
Third are third-party widgets and trackers: live chats, advertising pixels, analytics, social buttons. Each loads its own scripts from someone else's servers, whose speed you can't control. Over the years they pile up, and nobody remembers why some are there.
Two more common causes are embedded videos and slow hosting. A YouTube or Vimeo player loads a considerable amount of code before anyone presses play. And if the server is slow to answer the first request, other optimisations can only partly make up for the delay.
How to speed up your site
Most websites need the same fixes:
- Modern image formats. WebP and AVIF are usually noticeably smaller than JPEG or PNG at the same quality, and each image should be sized for the screen.
- Lazy loading. Images below the first screen only load when the visitor scrolls down to them. The main first-screen image, by contrast, loads straight away.
- A Content Delivery Network (CDN). Copies of your files sit on servers in different regions, and each visitor gets them from the nearest one.
- Caching. The browser and server keep ready-made files and pages instead of rebuilding them for every visit.
- Less JavaScript. Unused libraries and widgets are removed, and secondary scripts load after the main content.
- Click-to-play video. The page shows a light preview image and loads the player only on click.
If the server is still slow after all this, look at the hosting or the server-side code. Basic shared hosting suits a simple brochure site, but a shop with real traffic usually needs more resources.
How to measure speed
Start with Google's free PageSpeed Insights. It shows lab data, a single test on a simulated device that helps you find causes, and field data from real visitors over recent weeks, which is what Google relies on.
Field data only appears once a site has enough visitors. For the bigger picture, the Core Web Vitals report in Google Search Console groups your pages by status, separately for mobile and desktop.
Judge your results on real data, not a single test. Field data updates with a delay, so the effect of your fixes shows up after a few weeks rather than the next day.
Checklist
- Test your key pages in PageSpeed Insights, separately for mobile and desktop.
- Open the Core Web Vitals report in Search Console and find the pages with poor results.
- Convert images to WebP or AVIF and resize them to their on-screen size.
- Turn on lazy loading for everything below the first screen.
- Remove third-party scripts and widgets that nobody uses any more.
- Replace embedded videos with click-to-play previews.
- Set up a CDN and caching, and review your hosting if the server is slow to respond.
How we do it at IANKO
We build speed in from the design stage instead of patching it after launch. Our designers plan the first screen, fonts and images so that pages stay light, our Chief Technology Officer (CTO) owns the architecture and hosting, and our QA engineers and testers check the site on real phones and slow connections before every release. After launch, at the "make it better" stage, we track real Core Web Vitals data and fix whatever gets in your visitors' way.
The bottom line
A fast website won't sell for you, but it won't get in the way of selling either: people see your product, not a blank screen. Start with PageSpeed Insights and the Search Console report: they show which pages are slow and where to begin.