Picture a customer walking into a shop. They push the door, it sticks, and they stand on the footpath for three seconds waiting for it to open. Most people would not wait. They would walk to the shop next door. A slow website is that sticking door, except the shop next door is one tap away and the customer never tells you why they left.
Page speed is how quickly your website loads and becomes usable. Mobile optimisation is making sure it works properly on a phone, not just a desktop screen. The two are tied together, and both decide whether a visitor becomes a customer or a bounce. This explainer covers why speed costs or earns you money, how Google now measures it, why phones matter so much, and the practical levers that actually move the numbers.
Slowness costs you customers, in numbers
The link between speed and sales is not a hunch. Google, working with Deloitte, studied 37 leading retail, travel, luxury and lead-generation brand sites across more than 30 million user sessions and found that a 0.1 second improvement in mobile site speed increased conversion rates by 8.4% for retail sites and 10.1% for travel sites. Shoppers on the faster sites also spent 9.2% more.
Read that again, because the size of it is easy to miss. One tenth of a second. Not a redesign, not a new product, just a fraction of a second shaved off load time, and conversions move by roughly a tenth. For a small business, that is the difference between a quote form that gets filled in and one that gets abandoned halfway.
A bounce is when someone arrives on your site and leaves without doing anything: no second page and no enquiry. Slow pages produce bounces. The visitor was interested enough to click, then the wait drained the interest away. You paid for that click, through an ad or the time spent ranking the page, and got nothing back.
Core Web Vitals, in plain terms
A few years ago Google turned page experience into something it measures directly, through a set of metrics called Core Web Vitals. These feed into search engine optimisation, the practice of getting your pages to rank in search results, which means speed is now part of how high you appear on Google. There are three, and you do not need to be technical to understand what they describe.
Largest Contentful Paint (LCP) measures loading. It is the moment the biggest thing on the screen, usually your main image or headline, has finished appearing. Google's target is 2.5 seconds or less. Past that, the page feels sluggish before the visitor has even read a word.
Interaction to Next Paint (INP) measures responsiveness. When someone taps a button or opens a menu, how long before the page reacts? The target is 200 milliseconds or less, about a fifth of a second. A page that looks loaded but freezes when tapped fails this one. (INP replaced an older metric called First Input Delay, so if you have seen FID mentioned, this is its successor.)
Cumulative Layout Shift (CLS) measures visual stability. It is that annoying jump where you go to tap a link and an image loads above it, shoving everything down so you tap the wrong thing. The target is a score of 0.1 or less. Lower means the page holds still as it loads.
Google assesses these at the 75th percentile across mobile and desktop, which is a precise way of saying the experience has to be good for most of your visitors, not just the ones on fast phones and fast connections. You can check your own scores in Google's free PageSpeed Insights tool.
Most of your traffic is on a phone-shaped screen
Mobile is not a side consideration. Statcounter data for Australia puts mobile at 42.71% of web page views as of May 2026, against 54.67% for desktop and 2.62% for tablet. Roughly four in ten Australian visits arrive on a phone. For a local trade, a cafe, or a service people search for while out and about, that share is often higher still.
This is why "mobile optimisation" matters as its own discipline. A site can load quickly on a desktop with a big screen and a fast connection, then crawl on a mid-range phone over patchy mobile data. Buttons end up too small to tap, text needs pinching to read, and a form that takes thirty seconds on a laptop becomes a chore on a thumb. If four in ten visitors are on a phone and the phone experience is poor, you are turning away a large slice of demand before they reach your offer.
There is a newer reason to care, too. As people start asking AI answer engines for recommendations rather than scrolling a results page, the same fast, well-structured sites tend to be the ones these systems can read and cite. We have written about this shift from search to answer engines in how LLMs are changing search, and the foundations that help, clean code and clear structure, are the same ones that help your speed scores.
The practical levers that actually work
Most slow small-business sites are slow for a handful of fixable reasons. Here are the levers worth pulling, roughly in order of impact.
Optimise your images. Images are usually the heaviest thing on a page and the most common cause of a poor LCP score. Photos exported straight from a camera or phone can be several megabytes each. Compress them, size them to the dimensions they actually display at, and save them in a modern format like WebP or AVIF. Then apply lazy loading, a technique that defers off-screen images until the visitor scrolls near them. As MDN explains, this shortens what loads upfront, which "translates into reduced page load times".
Cache, and use a CDN. Caching stores a ready-made copy of your page so it does not have to be rebuilt from scratch on every visit. A content delivery network (CDN) takes that further by keeping copies of your site on servers around the world, so a visitor is served from one near them rather than from a single distant machine. For an Australian business with customers spread across the country, that cuts the physical distance your data travels.
Choose hosting that is built for speed. Cheap shared hosting crams many sites onto one overworked server, and your speed suffers for it. Good hosting gives your site room to respond quickly under load. This sits alongside getting your domain and DNS set up properly, which is the plumbing that points visitors to your site in the first place.
Keep the code lean. Many template and page-builder sites carry heavy bundles of code and scripts the page never really needs, and that weight drags down both LCP and INP. A lean site loads only what it uses. Clean, well-structured code also makes it easier to add things like schema markup, the labels that help search and AI tools understand your content.
How we approach it at Enki
We build sites to be fast from the first line of code rather than bolting on speed fixes afterwards. That means lean custom code instead of bloated templates, images and caching handled properly, and Core Web Vitals treated as a target to hit, not a report to ignore. We bring the same discipline to the systems behind a site: our Lead Management System build saved a client over 1,500 hours a month, and the principle is identical. Remove the friction and measure the result, and the speed does the selling. If your site feels slow or struggles on a phone, that is a fixable problem, and fixing it usually pays for itself in conversions you were quietly losing.