audit-speed_skill

Overview

This skill performs a deep Core Web Vitals and page speed audit with actionable root-cause analysis and prioritized fixes. It identifies why pages are slow, breaks down resource weight, and recommends targeted optimizations for LCP, CLS, INP, FCP, and TTFB. Use it to turn Lighthouse/PageSpeed data into a practical performance plan.

How this skill works

The skill inspects Core Web Vitals and related metrics, analyzes the LCP element, layout shift sources, main-thread blocking, and server response behavior. It produces a resource breakdown (HTML, CSS, JS, images, fonts, third-party) and a prioritized list of fixes with estimated impact. Where data is missing, it guides on collecting Lighthouse or PageSpeed Insights reports and necessary site context.

When to use it

• You need a root-cause diagnosis for slow page loads or poor Core Web Vitals.
• Planning performance improvements before a redesign or migration.
• Auditing landing pages with high bounce or low conversion due to speed.
• Evaluating third-party scripts and their impact on responsiveness.
• Preparing a prioritized developer task list for performance work.

Best practices

• Collect Lighthouse or PageSpeed Insights reports for the target URLs first.
• Identify the LCP element and ensure it’s not lazy-loaded; preload critical assets.
• Add explicit width/height or aspect-ratio for media to prevent CLS.
• Reduce main-thread work: code-split, defer non-critical JS, and break long tasks.
• Audit third-party scripts; defer or remove low-value scripts and consider self-hosting essential assets.

Example use cases

• Home page LCP is 5s: find whether TTFB, image, font, or render-blocking assets are the root cause.
• High CLS on product pages: detect missing image dimensions, ad slot shifts, or dynamic banners.
• Slow interactivity (high INP) on single-page apps: locate long tasks and heavy event handlers.
• Pre-launch checklist: ensure total page weight and JS/CSS budgets meet recommended thresholds.
• Post-audit handoff: create prioritized developer tasks with estimated impact for each fix.