Lighthouse Mechanic
Audit Core Web Vitals and auto-fix what's dragging your score down
Clients want rich pages and fast load times. This recipe runs Lighthouse, identifies the biggest performance bottlenecks, and drafts the fixes most likely to improve Core Web Vitals before handoff.
INGREDIENTS
PROMPT
Create a skill called "Lighthouse Mechanic". When I give you a website URL, run a Lighthouse performance audit. Identify the specific bottleneck for each Core Web Vital metric (LCP, CLS, INP, FCP, TTFB) — which element, script, or resource is the culprit. Then prepare fixes where possible: recommend lazy loading for below-fold images, add width/height attributes to images and embeds to prevent CLS, suggest font-display strategies and font subsetting, defer or async non-critical scripts, preload critical resources, and flag minification opportunities. Analyze the performance impact of each third-party script and recommend which to keep, lazy-load, or remove. Show a before/after comparison when changes can be tested. For issues that cannot be auto-drafted, provide specific code fixes with estimated score impact.
How It Works
Give your Claw a staging or live URL, and it runs a full Lighthouse
performance audit, diagnoses the issues dragging down Core Web Vitals,
and prepares a prioritized fix plan. Where source files are available,
it can also draft implementation changes for review.
What You Get
- Full Lighthouse audit with LCP, CLS, INP, FCP, and TTFB results
- Diagnosis of each metric's main bottleneck (which element, which script, which resource)
- Draft fixes for common issues: lazy loading below-fold images, width/height attributes, font-display, script defer/async, preload hints, minification opportunities
- Third-party script impact analysis (analytics, chat widgets, embeds, ad scripts)
- Font optimization suggestions: subsetting, preloading, fallback metric matching
- Before/after comparison when changes are tested
- Remaining issues with specific manual fix instructions
Setup Steps
- Give your Claw a URL (staging or live)
- Your Claw runs the audit and prepares a prioritized fix plan
- Review the recommended changes
- Apply the approved fixes
- Re-run to verify improvements
Tips
- Third-party scripts are often the biggest drag and the hardest to justify keeping
- Font subsetting can save substantial weight before you touch JavaScript
- Run this before handoff so performance is part of the deliverable, not a post-launch clean-up
- Save the before/after results so clients can see the impact of the work