Web Performance Audit

Measures Core Web Vitals and identifies render-blocking resources, network chains, layout shifts, and caching issues.

- Analyzes performance traces using Chrome DevTools MCP to extract FCP, LCP, TBT, CLS, Speed Index, and TTFB with detailed breakdowns

- Identifies render-blocking CSS/JS, network dependency chains, missing preloads, and caching header gaps through network request inspection

- Detects layout shift culprits (images without dimensions, injected content, font swaps) and accessibility gaps via DOM snapshots

- Requires chrome-devtools MCP server configured; provides checklist-driven audit workflow across performance, network, and accessibility phases

- Prioritizes findings by estimated impact and skips non-issues; biases toward live documentation over pre-trained thresholds

Web Performance Audit

Your knowledge of web performance metrics, thresholds, and tooling APIs may be outdated. Prefer retrieval over pre-training when citing specific numbers or recommendations.

Retrieval Sources

Source
How to retrieve
Use for

web.dev
https://web.dev/articles/vitals
Core Web Vitals thresholds, definitions

Chrome DevTools docs
https://developer.chrome.com/docs/devtools/performance
Tooling APIs, trace analysis

Lighthouse scoring
https://developer.chrome.com/docs/lighthouse/performance/performance-scoring
Score weights, metric thresholds

FIRST: Verify MCP Tools Available

Run this before starting. Try calling navigate_page or performance_start_trace. If unavailable, STOP-the chrome-devtools MCP server isn't configured.

Ask the user to add this to their MCP config: