Speed is the least glamorous part of a website and one of the most profitable. It affects whether people stay, whether they buy, and whether search engines show the site at all. Here is what the measurements mean, how to check yours, and what to fix first.

What Core Web Vitals measure

Google's three metrics each measure a different kind of frustration.

  • Largest Contentful Paint (LCP): how long until the main content is visible. Target under 2.5 seconds.
  • Interaction to Next Paint (INP): how quickly the page responds when someone taps or clicks. Target under 200 milliseconds.
  • Cumulative Layout Shift (CLS): how much the page jumps around while loading. Target under 0.1.

Why it affects revenue, not just rankings

The ranking effect is real but modest; it is a tiebreaker between similar pages. The conversion effect is larger. Across the stores and lead-generation sites we have measured, conversion rate drops noticeably for every second of load time on mobile, and bounce rate rises sharply once a page takes more than three seconds. A speed fix is often the cheapest conversion improvement available, because it applies to every visitor on every page.

How to check your own site

Run your homepage and your most important landing page through Google's PageSpeed Insights. Look at the 'field data' section first - that is what real visitors experienced over the last 28 days, and it is what Google uses. The lab score underneath is useful for diagnosis but it is not the ranking signal. If you have Search Console, the Core Web Vitals report shows which page groups fail and why.

The fixes that make the biggest difference

In rough order of impact, based on what we find on inherited sites.

  • Images: convert to WebP or AVIF, size them to the space they fill, and lazy-load everything below the fold
  • Scripts: remove tracking tags, chat widgets and plugins nobody uses; load the rest after the page is interactive
  • Hosting: move to modern hosting with a CDN so the first byte arrives quickly wherever the visitor is
  • Fonts: limit to two families, preload them and avoid the invisible-text flash
  • Layout shift: give images and embeds fixed dimensions so nothing jumps as it loads
  • Theme and plugin bloat: on WordPress and Shopify, the theme itself is often the heaviest thing on the page

How we build for speed

Every site we build is measured against Core Web Vitals on real devices before launch, and care plan clients get a monthly check so a new plugin or a heavy image never quietly undoes the work. Speed is not a feature we add; it is a constraint the whole build runs under.

Published · Last updated · By the Websitelift team