Your website opens instantly on your laptop. Then a customer tells you it "didn't load" on their phone. Both are true. A laptop on office Wi-Fi is several times faster than a mid-range Android phone on a 4G connection, and most of your visitors are on the phone.
In October 2026 we tested the websites of eight Indian startups that had just raised funding. On a typical phone, six of them took 10 seconds or more to show their main content, and four took over 20 seconds. Google considers anything over 4 seconds poor. These were well-funded companies with good-looking sites. The problems were invisible from a desk.
Here are the seven causes we find most often, roughly in order of how much damage they do.
First, measure it properly
Don't judge speed by opening your site on your own phone. Your phone has your site cached and is probably on Wi-Fi. Use a test that simulates a typical phone on a mobile network:
- Our free website check gives you the load time, what's slowing it down and the three fixes that matter, in about 30 seconds.
- Google PageSpeed Insights gives the same underlying Lighthouse data with more technical detail.
The number to watch is Largest Contentful Paint (LCP): how long until the biggest thing on screen (usually your hero image or headline) appears. Under 2.5 seconds is good. Over 4 seconds is poor.
1. Huge images
This is the cause in most of the sites we test. A photo straight from a camera or a stock site can be 3–8 MB. On a phone, that one image can take longer to download than the rest of the page combined.
How to spot it: your report lists "Properly size images" or "Serve images in next-gen formats" with large savings in kilobytes.
How to fix it: resize images to the largest size they are actually shown at (rarely wider than 2,000 pixels), and convert them to WebP or AVIF. A 4 MB JPEG hero usually becomes 150–300 KB with no visible difference. Most platforms, including Shopify and WordPress with the right plugin, can do this automatically.
2. The hero image loads last
Even a small hero image is slow if the browser discovers it late: for example, when it is set as a CSS background, injected by a slider script, or marked to "lazy load".
How to fix it: use a normal image tag for the hero, never lazy-load anything visible on first screen, and give the hero image high fetch priority. Lazy loading is great, but only for images further down the page.
3. Too much JavaScript
Every script has to download, then be parsed and run by the phone's processor, which is far slower than a laptop's. Page builders, sliders, animation libraries, chat widgets and pop-ups all add up. We regularly see sites shipping 2–3 MB of JavaScript to show a page of text and pictures.
How to spot it: "Reduce unused JavaScript" and a high Total Blocking Time in your report.
How to fix it: remove plugins and widgets you don't need, load the rest after the page has appeared, and prefer sections built in plain HTML and CSS over heavy page-builder blocks.
4. Third-party tags and widgets
Analytics, Facebook and Google Ads pixels, heatmaps, live chat, review widgets, embedded Instagram feeds, YouTube videos. Each one is code from someone else's server, and you have no control over how fast it is.
How to fix it: audit what is installed and remove anything nobody looks at. Load chat widgets only when someone clicks the chat button. Replace embedded YouTube players with a thumbnail that loads the video on click.
5. Web fonts
Custom fonts make a site look good, but four weights of two font families can easily add half a megabyte, and text can stay invisible until they arrive.
How to fix it: use two or three weights at most, self-host them in WOFF2 format, preload the one used in your headline, and set font-display: swap so text shows immediately in a fallback font.
6. Slow server or no caching
If your hosting takes a second or two just to start sending the page, everything else waits. This is common on cheap shared WordPress hosting.
How to spot it: "Reduce initial server response time" in your report.
How to fix it: turn on page caching, put the site behind a CDN, or move to a host that serves pre-built pages from servers close to your visitors. For a content site that rarely changes, a pre-rendered static site on a modern host is fast for almost nothing.
7. Layout that jumps around
Not strictly slowness, but it feels like it: the page appears, then an image or banner loads and pushes everything down just as the visitor goes to tap. Google measures this as Cumulative Layout Shift.
How to fix it: give every image and embed a width and height, and reserve space for banners and cookie bars instead of inserting them above the content.
Why it matters beyond Google
Speed is one of Google's page-experience signals, so a faster site does help in search. But the bigger effect is on people. Visitors who wait more than a few seconds leave before your page appears, and you never see them in your enquiries. Fixing speed turns more of the traffic you already have into customers, which makes it one of the cheapest growth projects available to most businesses.
Where to start
- Run a free website check on your home page and your most important landing page.
- Fix images first. It is usually the biggest win and the easiest.
- Remove scripts and widgets you don't need.
- Re-test, and repeat.
If you'd rather someone else did it, our Speed & Google fix for an existing site takes three to five days and comes with a before-and-after report. Get in touch and tell us your website address.