web-perf (Cloudflare): a Claude skill for Core Web Vitals audits

Cloudflare's web-perf skill has Claude audit a page's speed with browser traces and report Core Web Vitals, network and code fixes.

Installs: 116.4K; on skills.sh
Stars: 3.2K; on GitHub
Files: 1; besides SKILL.md
Updated: Oct 2026; last repo commit

web-perf makes Claude audit website loading and interaction performance in five phases: a performance trace, Core Web Vitals, network requests, an accessibility snapshot and a codebase check. It reports a Core Web Vitals table, prioritized issues with estimated impact, and specific fixes.

It is written around browser and performance tool calls such as navigate_page and performance_start_trace, and its setup notes point to the Chrome DevTools MCP server. If trace tools are missing, Claude continues with source and network analysis and says what it could not measure. It bundles no scripts.

Good for

Front-end developers fixing slow LCP, CLS or INP
Teams checking a site before launch against Lighthouse-style thresholds
Anyone auditing a third-party site without access to its code

Install web-perf

Claude Code

Copy this prompt.

Install the web-perf skill in Claude Code. Run this command:

npx skills add https://github.com/cloudflare/skills --skill web-perf

Then check that it loaded and tell me how to use it.

2
Paste it into Claude Code. It shows the change and asks before running it.

Requires Node.js.

From its listing on skills.sh. Source.

What's in the skill

When it loads

Audit, diagnose, or optimize website loading and interaction performance, Core Web Vitals, and Lighthouse performance scores.

Sections in SKILL.md

Retrieval Sources
FIRST: Verify MCP Tools Available
Key Guidelines
Quick Reference
Workflow
Phase 1: Performance Trace
Phase 2: Core Web Vitals Analysis
Phase 3: Network Analysis
Phase 4: Accessibility Snapshot
Phase 5: Codebase Analysis
Detect Framework & Bundler
Tree-Shaking & Dead Code
Unused JS/CSS
Polyfills
Compression & Minification
Output Format

Key facts

Author: Cloudflare
Repo: cloudflare/skills
Skill folder: skills/web-perf
skills.sh installs: 116,391
Repo stars: 3,244
License: Apache-2.0
Last repo commit: 2026-10-31
Bundled files: 1 file besides SKILL.md: references/skill-feedback.md
skills.sh audits: Gen Agent Trust Hub: pass; Socket: pass; Snyk: warn

What it includes

Check that browser and performance tools are available first
SKILL.md gives a chrome-devtools-mcp server entry for setup and says to change MCP configuration only if you authorized it.
Read · Verify MCP tools
navigate_page, then performance_start_trace with reload
Runs code · Phase 1: Performance trace
performance_analyze_insight for LCP, CLS, render blocking and document latency
Rates TTFB, FCP, LCP, INP, TBT, CLS and Speed Index as good, needs improvement or poor, using thresholds listed in the skill.
Network · Phase 2: Core Web Vitals
list_network_requests: render-blocking, chains, preloads, caching, large payloads
Network · Phase 3: Network analysis
take_snapshot: ARIA, contrast, focus, accessible names
Read · Phase 4: Accessibility snapshot
Bundler, tree-shaking, unused code, polyfills, compression; skipped for third-party sites
Read · Phase 5: Codebase analysis
Vitals table, top issues, recommendations, codebase findings
Output format

From the official docs

Permissions

Medium risk

Claude controls a browser and may help add an MCP server to your setup, which runs a package from npm. Only approve the MCP change if you want it, and audit sites you are allowed to test.

What it can do

Read your data
Create and change things
Delete things
Read-only mode

Watch out for

It can help add an MCP server
The setup entry runs chrome-devtools-mcp@latest through npx. SKILL.md says to change MCP configuration only within your authorized scope, so say no if you do not want it.
It loads whatever URL you give it
Claude navigates a real browser to the target page and reads network and page data. Point it at pages you are allowed to test.
Feedback can become a public GitHub issue
If you report bad guidance, references/skill-feedback.md has Claude draft an issue for cloudflare/skills and post it only after you see and approve the exact title and body. Issues are public.

Security advisories

No published security advisories as of Nov 2, 2026.

Technical details

Turning on read-only	No read-only switch is named in SKILL.md. The audit loads the page and reads trace, network and page data; the Output Format section asks for recommendations with code snippets or config changes.
Talks to	The URL you audit. Your AI provider receives the trace and page data Claude reads. github.com/cloudflare/skills (only if you approve a feedback issue)
Sign-in and keys	No account or key is named in SKILL.md.
Scopes	Drives a browser through Chrome DevTools MCP tools Reads your code for bundler and config findings May add an MCP server entry if you authorize it Can open a public GitHub issue on cloudflare/skills, only after you approve the exact text

Questions

What does web-perf do?

It makes Claude run a performance audit of a page using browser traces. It returns a Core Web Vitals summary, prioritized issues, specific fixes and, if it has your code, framework and bundler findings.

How do I install web-perf in Claude Code, Claude or Codex?

Use the install box at the top of the page and pick Claude Code, Claude or Codex. Claude Code and Codex read skills from a folder on your machine. In the Claude app you upload the skill folder as a zip.

Do I need Chrome DevTools MCP?

The audit relies on its tools, such as navigate_page and performance_start_trace. SKILL.md links the installation guide and gives a server entry that runs the chrome-devtools-mcp package through npx. Without trace tools, Claude falls back to source and network analysis.

Can it audit a site I do not own?

Yes for the browser phases. Phase 5, the codebase analysis, is skipped when you have no code for the site.

Does it need an API key?

SKILL.md names no key. It does need the browser tools to be connected.

Is it safe to use?

It bundles no scripts. It drives a browser to load the URL you give it and may suggest a Chrome DevTools MCP setup that runs a package through npx. SKILL.md says to change MCP configuration only within your authorized scope and otherwise ask first. A bundled feedback file lets Claude post a public GitHub issue, but only after you approve the exact text.

Information

updated Nov 2, 2026

Repository: cloudflare/skills
Folder: skills/web-perf

cloudflare/skills skills.sh

Sources

Docs, issue trackers and discussions this page is built from.

Show all 3

web-perf SKILL.md · github.com
web-perf on skills.sh · skills.sh
web-perf skill-feedback.md · github.com