Is your website slow on mobile? Five signs and what to do
Nobody waits for a page to load on 4G. A slow site loses visits before it shows anything, and almost always for the same reasons.
Ariadne Studio · 3 min read
In this article 7 sections
Summary
- Measure it with PageSpeed Insights, on mobile.
- Heavy images are the most common cause. Next come scripts nobody uses.
- If the server is slow to respond, switching hosting can be the cheapest improvement.
Speed is one of those things nobody praises, but everyone notices when it’s missing. On a phone with a spotty signal, every extra second on a blank screen is a chance for the visitor to go back to the search and tap a competitor. The good news: the reasons a site is slow are usually few and well known.
#How to measure it in two minutes
Open Google’s PageSpeed Insights, paste in the site’s address and look at the mobile result. It shows the three metrics Google uses to measure how a page feels to load and use, the Core Web Vitals:
- LCP (largest visible content): how long the main part of the screen takes to appear. The goal is 2.5 seconds or less.
- INP (response to interactions): how long the page takes to react to a tap. The goal is 200 milliseconds or less.
- CLS (visual stability): how much the page “jumps” while it loads. The goal is 0.1 or less.
#Sign 1: heavy images
This is the number one cause. A photo taken on a phone can be several megabytes. On the site, it needs to be the size it’s shown at and in a modern format like WebP or AVIF. Images further down the page should only load when the visitor gets to them.
#Sign 2: the page jumps while it loads
You go to tap a button and it moves because an image or an ad appeared above it. This happens when the space for each element isn’t reserved ahead of time. Setting the width and height of images fixes most cases.
#Sign 3: plugins and scripts nobody uses
Chat, pop-up, social media pixel, carousel, an extra font: each one adds code the phone has to download and run. List what’s installed and remove whatever doesn’t bring results. Often that cleanup alone makes the site faster.
#Sign 4: fonts and videos at the top
A background video on the first screen can look great on a computer and be far too heavy on a phone. Custom fonts have a cost too: use only a few weights and let the text show up even before the font loads.
#Sign 5: slow hosting
If the server is slow to respond, nothing that comes after makes up for it. Modern hosting serves files from servers close to the visitor and responds in milliseconds. If your site is on old shared hosting, switching may be the cheapest improvement there is.
#Where to start
Measure, fix the images, remove what isn’t used and measure again. Those three steps fix most slow sites. If the site is still heavy after that, the problem is in how it was built, and then it’s worth talking about a technical review or a redesign.
