Webperf Loading

A comprehensive loading performance toolkit that runs diagnostic JavaScript snippets directly in Chrome DevTools to pinpoint what's slowing down your page. It shines with its automated decision trees that chain diagnostics intelligently: slow TTFB triggers sub-part breakdowns, render-blocking detection flows into CSS and script audits, and third-party script analysis follows timing investigations. The 30+ snippets cover everything from TTFB sub-parts (DNS, connection, server) to font optimization, resource hints validation, and SSR hydration overhead. Created by Joan Leon, this is genuinely useful for methodical performance work where you need data-driven answers about what's actually blocking your renders or why your server response is sluggish.

skills.sh installs: 267
GitHub stars: 1.5K
last updated: Aug 21, 2026

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Install

$ npx -y skills add nucliweb/webperf-snippets --skill webperf-loading --agent claude-code

Installs into .claude/skills of the current project.

Files

WebPerf: Loading Performance

JavaScript snippets for measuring web performance in Chrome DevTools.

Running a script

Run the script with mcp__chrome-devtools__evaluate_script, passing the file instead of its code: sourcePath with the absolute path of scripts/<Name>.js in this skill, and format: "script", since a script runs by itself and is not a function. Read the object it returns. The scripts have no console output, so the returned object is the result: script, status and the metric data (value, rating, details, items, issues), as described in references/schema.md.
When status is "tracking", the script keeps observing the page. After the interactions, call the function named in getDataFn with another mcp__chrome-devtools__evaluate_script call, as an arrow function in function, for example () => getINP(), and read the object it returns.
When status is "error" or "unsupported", read error: the page may not have loaded yet, or the browser lacks the API.