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Performance optimization from render-path evidence

Core Web Vitals risk signals for LCP, INP, CLS, delivery, images, fonts, bundles, and third parties.

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Content & schema
50tests fired in this category
modules
8dedicated content & schema checks
every scan
299+tests across all categories

Why it matters

A passive crawl cannot reproduce every user's network or interaction, but it can expose a clogged critical path. Lazy hero images, shifting media, oversized bundles, and vendor tags are actionable causes before lab or field numbers arrive.

How it works

The evaluator checks LCP render-path hints, INP main-thread risk, CLS dimensions and font shifts, CDN and cache headers, initial and lazy chunk weight, image format and sizing, third-party count and weight, and font hosting, count, and preload behavior. Thresholds include 2.5s LCP, 200ms INP, 0.1 CLS, and 800ms TTFB as targets.

Site impact

Unreserved media can move content, heavy JavaScript can delay interaction, and render-blocking work can postpone the first useful view. The combined cost is slower mobile experiences and less headroom for forms, navigation, and conversion paths.

How FixWeb tests for it

FixWeb reads rendered resource statistics, script and font inventories, image attributes, and response headers, with a model pass over likely render-path risk. It does not measure real-user p75 Core Web Vitals, CrUX, Search Console reports, or interaction timing in this evaluator.

How to improve

Prioritize the LCP image with modern format, dimensions, and eager loading; reserve media space; split and defer JavaScript; remove or delay unjustified third parties; and serve a small self-hosted woff2 set with sensible preload and font-display behavior.

Run it on your own site

Keep improving while FixWeb keeps watch.

FixWeb crawls public pages like a real browser, then organizes crawl, search, content, accessibility, performance, media, form, runtime, browser-compatibility, owner-data, and repo findings into practical improvement prompts for Cursor, Claude, and Copilot.

  • $9 once, no subscription
  • Just paste a URL — we crawl, analyze, and report
  • Severity-graded quality issues, deduped to signal only
  • Current, AI-ready improvement prompts you can paste into Cursor, Claude, Copilot
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