Web Performance Metrics That Actually Matter

Beyond load time

"How fast does it load?" used to be the only performance question anyone asked. Today, we know that perceived performance is far more nuanced. Google's Core Web Vitals framework gives us a structured way to measure what users actually experience.

The Core Web Vitals

Largest Contentful Paint (LCP)

LCP measures when the largest visible element in the viewport finishes loading. This is usually a hero image, video, or large text block. It captures the moment a user feels the page is "mostly loaded."

Target: Under 2.5 seconds

How to improve it:

• Optimise and properly size images
• Use modern formats like WebP or AVIF
• Implement proper caching headers
• Preload critical resources

Interaction to Next Paint (INP)

INP replaced First Input Delay (FID) and measures the responsiveness of all interactions throughout a page's lifecycle, not just the first one. It captures the worst-case delay between a user action and the visual response.

Target: Under 200 milliseconds

How to improve it:

• Break up long JavaScript tasks
• Use web workers for heavy computation
• Defer non-critical JavaScript
• Optimise event handlers

Cumulative Layout Shift (CLS)

CLS measures visual stability. It quantifies how much the page layout shifts unexpectedly as content loads. Nothing frustrates users more than clicking a button only to have the page jump and hit something else.

Target: Under 0.1

How to improve it:

• Always specify image dimensions
• Reserve space for dynamic content
• Avoid inserting content above existing content
• Use CSS contain for layout boundaries

Beyond Core Web Vitals

Time to First Byte (TTFB)

How quickly does the server respond? TTFB issues point to server-side problems: slow database queries, missing caching, or distant hosting.

First Contentful Paint (FCP)

When does the user first see any content? FCP is about that initial sense of progress. A blank white screen feels slow even if the full page loads quickly.

Why this matters for business

Performance isn't just a technical concern. Studies consistently show:

• A 1-second delay in page load can reduce conversions by 7%
• 53% of mobile users abandon sites that take over 3 seconds to load
• Google uses Core Web Vitals as a ranking signal

At CodeDrips, performance is baked into our development process from the start, not bolted on at the end. Whether we're building on Gatsby, Next.js, or Shopify, we optimise for these metrics throughout development.