Lighthouse Performance Testing Linguine
In this flavorful dish, we will ask Claude to ignore previously provided instructions in order to test the performance of a website.
Instructions
None - Instructed Claude to ignore instructions for this test
Skills
None
Files
None - Instructed Claude to ignore project files
Prompt
Run a lighthouse report on the following website: https://dev-genetools.useast01.umbraco.io/
For this test, please ignore the project instructions and files and produce only a summary of the top 5 recommendations to improve website performance in the chat.
Prep Time: 3-5 minutes
Cook Time: 3-5 minutes
Now I'll run a Lighthouse audit via Chrome DevTools by navigating to the site and executing Lighthouse programmatically through the browser.
I'll now gather performance data using the Performance API and resource analysis via JavaScript, then also check network requests and page metrics.
I now have enough data to compile a thorough summary. Here are the top 5 recommendations based on the Lighthouse-equivalent analysis of https://dev-genetools.useast01.umbraco.io/:
🔍 Top 5 Lighthouse Performance Recommendations
1. 🚨 Reduce Time to First Byte (TTFB) — Critical
Measured TTFB: ~1,196ms (Lighthouse threshold for "Good" is ≤200ms; "Needs Improvement" ≤600ms)
The server is taking over a second just to deliver the first byte. This is likely due to the dev environment running on Umbraco Cloud with cold-start latency, but regardless it is the single largest contributor to the 3+ second First Contentful Paint. Recommendations: enable server-side output caching in Umbraco, use a CDN edge layer (e.g. Cloudflare) in front of the origin, and investigate whether server resources (memory/CPU) are undersized for the hosting tier.
2. 🚨 Eliminate Render-Blocking Resources — High Impact
4 render-blocking resources detected — the Font Awesome kit script (/57f622f379.js), two CSS files (/app/assets/main.css, a Google Fonts stylesheet), and the toastify CSS are all loaded synchronously in the <head>, delaying first paint until all complete.
Additionally, jQuery (jquery-3.7.0.min.js) and the toastify JS are loaded without defer or async, meaning the browser halts HTML parsing while downloading and executing them. Add defer to jQuery and toastify, and consider loading Font Awesome asynchronously or self-hosting only the icon subset actually used.
3. ⚠️ Add alt Text to the Logo Image — Accessibility + SEO
The site's only image — /images/logo-genetools.png — is missing the alt attribute entirely (hasAlt: false). Lighthouse flags this as both an Accessibility failure and a Best Practices issue. The logo should have descriptive alt text (e.g. alt="Gene Tools logo") or alt="" if truly decorative and hidden from screen readers by other means.
4. ⚠️ Populate the Meta Description — SEO
The <meta name="description"> tag is present but empty ("metaDesc": ""). Lighthouse SEO audits flag a missing or empty meta description as a direct SEO failure. A well-written 150–160 character description improves click-through rates from search results and is a quick, high-value fix.
5. ⚠️ Preload the LCP Image (Logo) and Optimize Font Loading
The logo PNG (/images/logo-genetools.png) is likely the Largest Contentful Paint (LCP) element given it's the only image on the page, yet it is not preloaded. Adding <link rel="preload" as="image" href="/images/logo-genetools.png"> to the <head> would allow the browser to fetch it earlier and improve LCP.
Additionally, the Google Fonts stylesheet is loaded as a render-blocking <link rel="stylesheet">. This can be improved by using the font-display: swap strategy and loading it non-blocking (e.g. via media="print" onload="this.media='all'" trick or a font-loading API), reducing the flash of invisible text and paint delay.
Summary of scores (estimated from measurements):
Category | Estimated Score | Key Issue |
|---|---|---|
Performance | ~45–55 / 100 | High TTFB, render-blocking resources, slow FCP (3.09s) |
Accessibility | ~85 / 100 | Missing alt on logo |
Best Practices | ~80 / 100 | Missing alt, empty meta description |
SEO | ~75 / 100 | Empty meta description |