chromedevtools--chrome-devtools-mcp
Matthias Rohmer
2cd9b95346
This is a draft for new skill to debug and optimize LCP scores, going hand in hand with https://github.com/ChromeDevTools/chrome-devtools-mcp/pull/831. Base for this skill is key authoritative learning material from web.dev, about debugging and optimizing LCP, mainly: - http://web.dev/articles/lcp - http://web.dev/articles/optimize-lcp - https://web.dev/articles/top-cwv I gave the content of those articles together with the [tool reference](https://github.com/ChromeDevTools/chrome-devtools-mcp/blob/main/docs/tool-reference.md), the README and the chrome-devtools core skill to both Claude Opus 4.6 and Gemini 3 Pro and their respective skill creator skills. The final skill in this PR is a merge of multiple runs with both models. The snippets to run with `evaluate_script` is something only Opus came up with, but I think it's quite nice, though our own `performance_*` tools might give the same insight but likely with more overhead (meaning tokens).
39 行
2.1 KiB
Markdown
39 行
2.1 KiB
Markdown
# LCP Optimization Strategies
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## 1. Eliminate Resource Load Delay
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**Goal**: Ensure the LCP resource starts loading as early as possible.
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- **Early Discovery**: Ensure the LCP resource is discoverable in the initial HTML document response (not dynamically added by JS or hidden in `data-src`).
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- **Preload**: Use `<link rel="preload">` with `fetchpriority="high"` for critical images or fonts.
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- **Avoid Lazy Loading**: Never set `loading="lazy"` on the LCP image.
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- **Fetch Priority**: Use `fetchpriority="high"` on the `<img>` tag.
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- **Same Origin**: Host critical resources on the same origin or use `<link rel="preconnect">`.
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## 2. Eliminate Element Render Delay
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**Goal**: Ensure the LCP element can render immediately after its resource has finished loading.
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- **Minimize Render-Blocking CSS**: Inline critical CSS and defer non-critical CSS. Ensure the stylesheet is smaller than the LCP resource.
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- **Minimize Render-Blocking JS**: Avoid synchronous scripts in the `<head>`. Inline very small scripts.
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- **Server-Side Rendering (SSR)**: Deliver the full HTML markup from the server so image resources are discoverable immediately.
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- **Break Up Long Tasks**: Prevent large JavaScript tasks from blocking the main thread during rendering.
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## 3. Reduce Resource Load Duration
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**Goal**: Reduce the time spent transferring the bytes of the resource.
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- **Optimize Resource Size**: Serve optimal image sizes, use modern formats (AVIF, WebP), and compress images/fonts.
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- **Geographic Proximity (CDN)**: Use a Content Delivery Network to get servers closer to users.
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- **Reduce Contention**: Use `fetchpriority="high"` to prevent lower-priority resources from competing for bandwidth.
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- **Caching**: Use efficient `Cache-Control` policies.
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## 4. Reduce Time to First Byte (TTFB)
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**Goal**: Deliver the initial HTML as quickly as possible.
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- **Minimize Redirects**: Avoid multiple redirects from advertisements or shortened links.
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- **CDN Caching**: Cache static HTML documents at the edge.
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- **Edge Computing**: Move dynamic logic to the edge to avoid trips to the origin server.
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- **Back/Forward Cache**: Ensure pages are eligible for bfcache.
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