Most businesses treat site speed as a technical detail, something to ask the developer about once a year. It is a marketing number. If a paid click lands on a page that takes four seconds to show anything, part of that click was bought for nothing.

What to measure

Three numbers cover most of it, and Google uses all three in its Core Web Vitals:

  • Largest Contentful Paint: how long until the main picture or headline appears. Aim for under 2.5 seconds on a phone.
  • Interaction to Next Paint: how quickly the page responds to a tap. Aim for under 200 milliseconds.
  • Cumulative Layout Shift: how much the page jumps while loading. Aim for under 0.1.

A lab test on a fast office connection tells you little. What matters is how the page behaves for the people who actually visit, on their phones, on their networks.

Measure it in the visitor’s browser

Every modern browser records how a page loaded. A few lines of script can read those figures and show or send them. This is the code that runs the live meters on our homepage:

// how long the page took, measured by the visitor's own browser
const nav = performance.getEntriesByType('navigation')[0];
const files = performance.getEntriesByType('resource');
const bytes = [nav, ...files].reduce((sum, e) => sum + (e.transferSize || 0), 0);
console.log('Loaded in', Math.round(nav.loadEventStart), 'ms');
console.log('Transferred', Math.round(bytes / 1024), 'KB in', files.length + 1, 'files');
A budget beats a targetSet a page weight limit before design starts, for example 700 KB on first load, and treat going over it as a bug. Targets get missed quietly; budgets get argued about.

Where the weight usually goes

  1. Pictures saved at camera size. Converting to WebP or AVIF at the size they are shown often cuts them by 80 percent.
  2. Video that loads before anyone scrolls to it.
  3. Page builders and plugins that load their code on every page, used or not.
  4. Third-party scripts: chat widgets, trackers and embeds, each with its own files.
The fastest file is the one the page never asks for.The rule we build every site to

Speed work is rarely glamorous. It is one of the few changes that improves every campaign at once, and it keeps paying for as long as the site is live.