Why website speed matters
How to measure loading speed, responsiveness and layout stability, then fix the delays visitors notice.
Part of the series: Website Fundamentals
Part 1 / 5
Contents
A menu that takes too long to open or a booking button that moves as you tap it can interrupt a sale. Website performance is about those moments: how soon people can read the page, whether controls respond, and whether the layout stays in place.
There is no universal percentage of customers you lose for each extra second. Measure your own site and start with the pages people use to contact you, book or buy.
What to measure
The current Core Web Vitals are LCP, INP and CLS. INP replaced the older FID metric in 2024.
| Metric | What it measures | Good threshold |
|---|---|---|
| LCP, Largest Contentful Paint | When the largest visible content element appears | 2.5 seconds or less |
| INP, Interaction to Next Paint | How quickly the page displays a response to an interaction | 200 milliseconds or less |
| CLS, Cumulative Layout Shift | Unexpected movement of page elements | 0.1 or less |
These targets apply at the 75th percentile of visits, assessed separately for mobile and desktop. See Google’s Web Vitals guidance.
Read the test results carefully
PageSpeed Insights can show both real-visitor data and a simulated Lighthouse test. Small sites may not have enough traffic for real-visitor results. A Lighthouse score helps diagnose problems, but it does not describe every visitor’s experience or predict a Google ranking.
Test more than the homepage. A product page with several photos may behave very differently from a short contact page. Also try the site on a phone using mobile data.
Fix the largest delays first
- Images: resize them for their display size, compress them and use suitable formats. Load images farther down the page lazily, but let the main image load promptly.
- JavaScript: remove unused scripts and delay optional widgets. Check whether a chat or booking embed blocks the first screen.
- Layout: reserve space for images and embeds so that content does not jump when they arrive.
- Fonts and styles: load only what the page uses. Avoid hiding readable content behind an entrance animation.
- Caching: reuse unchanged assets while making sure visitors receive new versions after an update.
A static site built with Hugo can reduce work on the server, but large images and heavy scripts can still make it slow.
After each change, repeat the same test and check that forms and navigation still work. Keep a record so that later updates can be compared with a known result.
Send us your site if you want help identifying the delays that matter most.