Web performance: why your site is slow on mobile and how to fix it

Every second of loading delay can cost you customers. And the problem is not hypothetical: most visits to a website come from a phone, often on a mobile connection and on a small screen.

The good news is that almost everything that slows a website down can be measured and fixed. This guide orders the actions by their real impact.

Measure before you change anything

Without a measurement, every improvement is an opinion. You need three things: how long your site takes to appear, where that time goes and which pages are the slowest.

• The time until the content appears (LCP) is the number people feel most.
• The weight of each image and script is the most common cause of slow websites.
• Real user data (Core Web Vitals) takes precedence over lab tests.

Images: half of the problem

A 3 MB photo shown on a 6-inch phone is money wasted. Serve images in modern formats such as WebP, resize them to the size they are actually displayed at and delay loading everything below the first screen.

• Serve the image at the exact size each screen needs.
• Reserve the space of the image so the page does not jump while loading.
• Lazy-load everything that sits below the first screen.

Code that adds nothing

Every script you load is time your phone has to process. Plugins, chat widgets, tracking pixels and animations pile up without anyone reviewing them, and the whole site ends up slower.

• Review which scripts are essential and which can load later or only on certain pages.
• Remove the plugins nobody uses.
• Keep dependencies up to date: an outdated version can cost you more than the update itself.

Hosting and caching

A good server with a properly configured cache delivers the page in milliseconds instead of seconds. If your site slows down when more visits arrive, the problem is probably not in the design.

• Check that page caching and asset caching are both enabled.
• Use a CDN if your audience is spread across several countries.
• Review your hosting plan: a cheap one shows during peak hours.

Where to start this week

Do not try to fix everything at once. Measure, find the slowest page and the heaviest resource, fix that one first and measure again. Speed improves in a sustainable way when every change is verified, not when assumptions pile up.