Website load time: how a slow site costs you customers

Short answer: a slow website loses customers before they have read a word. According to Google and SOASTA (2017), the chance that a mobile visitor leaves rises by 32 % when a page takes 3 seconds instead of 1, by 90 % at 5 seconds and by 123 % at 10 seconds. The target is simple: the main content should appear within about 2.5 seconds on a phone.

Speed is one of the few website problems you can measure exactly and fix for good. It also affects three things you care about: whether visitors stay, whether they enquire and how Google and AI systems treat your pages. This article shows the figures with sources, what to aim for and where the time usually goes.

What does the research say about load time and visitors leaving?

The best-known figures come from Google and the research firm SOASTA, who analysed mobile visits in 2017 and published how the probability of a visitor bouncing (leaving after one page) grows with load time. Compared with a page that loads in 1 second:

These are relative increases in probability, not shares of all visitors, and the data is from 2017. Phones and networks have improved since, but the principle holds: waiting costs visitors.

A second source looks at money instead of bounces. In “Milliseconds Make Millions” (Deloitte, commissioned by Google, 2020), researchers analysed mobile data of 37 brands in retail, travel, luxury and lead generation across Europe and the US. A site that became 0.1 seconds faster saw retail conversions rise by 8.4 % and travel conversions by 10.1 %. That is an average over those brands under study conditions, not a promise for your shop, but the direction is clear.

What counts as fast in 2026?

Google measures real visitors’ experience with the Core Web Vitals. A page is rated good when, for most visits:

These figures are part of Google’s page experience signals. They are one signal among many, so a fast but empty page will not beat a strong one. But among comparable pages, the faster and steadier one has the edge, and visitors notice either way.

Why is my website slow?

In our audits the same five causes come up again and again:

1. Oversized images. Photos straight from the camera or in old formats. Modern formats (WebP, AVIF) sized to the screen often cut the weight dramatically.
2. Too many scripts and plugins. Every tracking tool, chat widget, slider and plugin adds code that the phone has to load and run. This is common on WordPress sites with many plugins.
3. Slow hosting or no caching, so every visit rebuilds the page from scratch on a busy shared server.
4. Heavy themes and page builders that ship a lot of code the page never uses.
5. Fonts and videos that load late or block the page. Self-hosted fonts and videos that only start on demand help.

How do you measure your own site?

• PageSpeed Insights (pagespeed.web.dev) shows lab results and, when enough visits exist, real-visitor data for your page.
• Search Console has a Core Web Vitals report grouping all your pages by status.
• Test on a real phone on mobile data, not only on office wifi. That is how most customers see your site.

Look at the mobile result first. Our free website check covers the main technical points in one pass.

What can you do about it?

• Compress and resize images, serve modern formats and load below-the-fold images lazily.
• Remove what you do not use: plugins, old tracking tags, unused fonts.
• Choose hosting in the EU with a content delivery network (CDN), so pages are served close to the visitor.
• Cache pages instead of generating them on every visit.
• If the foundation is the problem, change the foundation. A site built on Next.js delivers server-rendered pages that load quickly and read well for search engines and AI crawlers. Moving from a plugin-heavy WordPress site is covered in WordPress to Next.js, and the order of work in website relaunch without losing SEO.

Speed is also part of how we build every site: images optimised, scripts kept to what is needed, and Core Web Vitals checked before launch.

Written byPatryk WisniewskiLead developer

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