Website loads slowly on mobile: causes and how to fix it
Most shoppers visit websites from their phones, and if a page takes longer than 3 seconds to load, many of them simply close it. The ad budget is spent, but there is no order. Here is how to check your website speed on mobile yourself, the most common causes of a slow site, and what to do about them.
1. How to check website speed in 2 minutes
Open Google's free PageSpeed Insights, paste your website address and click "Analyze". Look at the "Mobile" tab: it shows how your site loads on a phone, and it is the one Google relies on.
Check not only the homepage but also the product or service page your ads lead to. Often the homepage is fast while a product page with a dozen photos loads twice as long.
2. What the PageSpeed numbers mean
- Score from 0 to 100. 90 and above is good, 50-89 needs improvement, below 50 is poor.
- LCP (Largest Contentful Paint). When the main block of the page appears: a large banner, photo or heading. Google's target: under 2.5 seconds.
- INP. How fast the page responds to a tap. Target: under 0.2 seconds.
- CLS. Whether elements jump while loading, just as someone is about to tap a button. Target: under 0.1.
The "Diagnostics" block below lists specific causes. Don't be put off by a long list: usually 2-3 items give 80% of the result.
3. 7 reasons a website is slow on mobile
- Heavy images. The most common cause. A 3-5 MB photo straight from the camera, while on a phone screen it takes 400 pixels. Fix: compress images, use the WebP format and set the right size.
- Extra scripts and widgets. Live chat, several ad pixels, a reviews widget, popups. Each script loads from another server and slows the page down. Keep only what actually brings leads.
- Slow hosting. If the server responds slowly (PageSpeed shows a long server response time), no page optimization can make up for it.
- Heavy theme or page builder. Multipurpose WordPress themes and visual builders load code for every possible feature, even the ones you don't use.
- Fonts. Several font weights from an external service delay the moment text appears.
- Jumping elements. A banner or image without a set size appears later and pushes the text down. People tap the wrong thing and get annoyed.
- No caching. Without caching, the browser downloads the same files again on every visit.
4. Shopify, WooCommerce or a marketplace store: what you can do
On a hosted platform you can't change the core code, but as a store owner you still affect speed:
- upload product photos in a sensible size, not 5 MB each;
- remove extra banners and sliders from the homepage: 1-2 instead of 6;
- don't install several chats and widgets at once;
- on Shopify, review installed apps: many add their own script to every page, and sometimes their code stays in the theme even after the app is removed.
5. Example: from 99 to 100 on mobile
The website you are reading this on started with a mobile score of 99 for performance and 94 for accessibility. After the fixes it scored 100/100/100/100:
- images converted to WebP with exact sizes, and the main image loads first;
- critical styles inlined, so nothing blocks the first render;
- text and button contrast fixed;
- layout shift removed (CLS from 0.106 to 0).
If your website doesn't show up in search at all, read "Why your website isn't on Google".
6. When to call a specialist
If you've already compressed images and removed extra widgets but the score is still below 50, the cause is usually deeper: the theme, a page builder, hosting or the code itself. Then it's better to start with an audit and find out what exactly slows the site down, instead of installing random "speed" plugins that often add even more code.
In short
- Check speed in PageSpeed on the "Mobile" tab.
- Google's targets: LCP under 2.5 s, INP under 0.2 s, CLS under 0.1.
- The usual culprits are images, extra scripts and slow hosting.
- You can speed up a hosted store too: images, banners, apps.
- If simple fixes don't help, start with an audit.
FAQ
What website speed is considered good?
Google's targets for mobile: the main block of the page (LCP) appears within 2.5 seconds, the page responds to a tap within 0.2 seconds (INP), and elements don't jump while loading (CLS under 0.1). A PageSpeed score of 90 or more is considered good.
Does speed affect Google rankings?
Yes, page speed and stability are among the signals Google uses. But speed affects sales even more: people on phones rarely wait more than 3 seconds and go back to search to a competitor.
Can I speed up a Shopify store?
Partly. You can't change the platform code, but you can compress images, remove unused apps and third-party scripts, and simplify the homepage. This often gives a noticeable boost.
How long does speed optimization take?
Simple fixes (images, extra scripts) take 1-2 days. If the problem is the theme, a page builder or hosting, there is more work, and it's worth starting with an audit so you don't pay for things you don't need.
I set up Google Shopping, Google Ads and SEO for online stores and small businesses. I write in plain language, no fluff. If something from this article doesn't work for you, message me and I'll help.
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