Core Web Vitals: The SEO Speed Checklist for Business Websites

Website speed is not a vanity metric. It affects how many people stay, how many convert, and — through Core Web Vitals — how Google ranks you. The good news is that most sites are slow for a small number of very fixable reasons.

The three metrics that matter

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

Measure on a mid-range Android phone over a normal mobile connection. Measuring on your laptop over office fibre tells you almost nothing about your actual users.

Images: the usual culprit

1. Serve modern formats (WebP or AVIF) instead of oversized PNG and JPEG.
2. Resize to the largest size actually displayed — do not ship a 4000px photo into a 600px slot.
3. Always set width and height attributes. This alone kills most layout shift.
4. Lazy-load anything below the fold; never lazy-load the hero image.
5. Compress. Aggressively. Most photos survive it perfectly well.

Fonts

Custom fonts commonly cost a full second. Preconnect to the font host, preload the one or two weights you actually use, set font-display: swap, and delete the six weights you loaded and never used.

JavaScript

Every script blocks something. Audit what is really on the page: three analytics tools, a chat widget, a heatmap, a carousel library used once. Defer what is not critical, remove what is not used, and be honest about which marketing tags are actually earning their millisecond cost.

Server and caching

• Enable Gzip or Brotli compression.
• Set long cache headers for static assets and version the filenames.
• Put a CDN in front of the site so assets are served near the user.
• Cache database queries and rendered pages where content does not change per visitor.
• Fix slow queries — a 900ms database call is a 900ms delay for every visitor.

The on-page SEO basics that still decide rankings

Speed is necessary but not sufficient. Alongside it:

• A unique, descriptive title and meta description on every page.
• One clear H1, and a logical H2/H3 structure beneath it.
• Descriptive alt text on meaningful images.
• Clean, readable URLs.
• Structured data (Organization, Service, Article, Product) for rich results.
• A valid sitemap.xml and a sensible robots.txt.
• Internal links that actually help someone navigate.

Run this quarterly, not once

Performance decays. A new tracking script, an uncompressed image uploaded by a colleague, a plugin update — and you are back over budget. Put a quarterly Lighthouse run in the calendar and treat regressions as bugs.

Every site we build ships with these checks baked into the process — see our web development service for what that includes.