Agent skill · practicalswan
performance
Optimize web performance for faster loading and better user experience. Use when asked to \"speed up my site\", \"optimize performance\", \"reduce load time\", \"fix slow loading\", \"improve page speed\", or \"performance audit\".
What it needs
About 8k tokens when loaded.
What this skill does
Performance optimization Evidence-led performance optimization using real-user signals for prioritization and browser traces for diagnosis. Focuses on loading speed, runtime responsiveness, and resource delivery. How it works 1. If a page can run, read the measurement workflow and establish a field-plus-lab baseline before editing. 2. Prioritize poor real-user Core Web Vitals. Use a DevTools performance trace and its focused insights to find the cause. 3. Inspect and change only the code or assets connected to measured bottlenecks. 4. Re-run equivalent lab measurements and report before/after values, conditions, and uncertainty. Field verification remains pending until enough new user data arrives. When no runnable page exists, perform static inspection but call findings hypotheses, not measured regressions. Include the command or browser workflow that can verify each high-impact hypothesis. Prefer a browser tool that records a performance trace and exposes focused insights. With Chrome DevTools MCP, use performancestarttrace and performanceanalyzeinsight; do not route performance through lighthouseaudit, which covers non-performance Lighthouse categories. Starting performance budget Budgets must reflect the product's target devices, networks, page types, and user journeys. The values below are initial guardrails for a typical content or commerce page, not universal pass/fail criteria. Preserve an existing project budget when one is already defined. Resource Budget Rationale ---------- -------- ----------- Total page weight < 1.5 MB Bounds transfer time and data cost on constrained target networks; calibrate with representative pages JavaScript (compressed) < 300 KB Protect parse and execution cost CSS (compressed) < 100 KB Limit render-blocking work Images (above-fold) < 500 KB Protect likely LCP resources Fonts < 100 KB Limit critical font transfer Third-party < 200 KB Bound code outside product control Critical rendering path Server response TTFB < 800ms. …
How to use it
Reference it in AdaL, Claude Code, Cursor or any coding agent — nothing to install:
@skills practicalswan/performance