web-perf

web-perf is a skill for Claude Code from fcakyon/claude-codex-settings. It costs 26 tokens per session (2,057 once invoked), scanned A, a copy of web-perf, Apache-2.0.

A website performance auditing and troubleshooting workflow. It examines loading speed, interaction performance, Core Web Vitals, and Lighthouse scores; Core Web Vitals are Google's measures of important user-facing web performance.

In plain words
What is it for?
Use it to audit a site, inspect browser performance traces, analyze network or loading issues, and improve Lighthouse or Core Web Vitals results.
Why use it?
It helps identify why a site loads slowly or responds poorly, while making clear when required browser measurements are unavailable. It also avoids relying on outdated performance limits or recommendations.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the cloudflare-skills plugin — 16 skills shipped together

Good fit Use it to audit a site, inspect browser performance traces, analyze network or loading issues, and improve Lighthouse or Core Web Vitals results.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/fcakyon/claude-codex-settings/web-perf
About the project

claude-codex-settings is a collection of configurations and reusable extensions for Claude Code, OpenAI Codex, Cursor, and related coding tools. Developers use its skills, commands, hooks, agents, plugins, and MCP servers to shape coding-agent workflows and connect alternative model APIs. The catalogue entries are components of this collection that can be installed into supported coding tools.

fcakyon/claude-codex-settings · 1,181 stars · on GitHub · claudesettings.com

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add fcakyon/claude-codex-settings --skill web-perf
Clone the repo
git clone --depth 1 https://github.com/fcakyon/claude-codex-settings

Made for: Claude Code.

Or install cloudflare-skills, the plugin that ships this one along with the rest of its 16 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for web-perf

README.md
[![agentmods](https://agentmods.dev/badge/skills/fcakyon/claude-codex-settings/web-perf/github.svg)](https://agentmods.dev/skills/fcakyon/claude-codex-settings/web-perf)
Your own site
<a href="https://agentmods.dev/skills/fcakyon/claude-codex-settings/web-perf"><img src="https://agentmods.dev/badge/skills/fcakyon/claude-codex-settings/web-perf/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for web-perf

Your own site · 80×15
<a href="https://agentmods.dev/skills/fcakyon/claude-codex-settings/web-perf"><img src="https://agentmods.dev/badge/skills/fcakyon/claude-codex-settings/web-perf.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 26 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,057 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 83% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00026 $0.02057
Opus 5.5 $0.00010 $0.00823
Sonnet 5.5 $0.00005 $0.00411
Haiku 4.5 $0.00003 $0.00206

Measured 1mo ago against content hash 4590171d2252, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

web-perf scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

83% identical to web-perf — 1 line differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

plugins/cloudflare-skills/skills/web-perf/SKILL.md · 203 lines

How it starts

The opening of the file, as written. The whole thing — 203 lines — stays where its author put it; the contents beside it link to each section on GitHub.

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

Discover available browser and performance tools before starting. Use the capabilities available for the requested audit. If trace tools are unavailable, continue any useful source or network analysis and state which measurements could not be collected.

If the user wants Chrome DevTools MCP setup, consult its installation guide and use the latest package version. Only change MCP configuration when setup is within the user's authorized scope; otherwise ask first. For clients using command and args, an example server entry is:

"chrome-devtools": {
  "command": "npx",
  "args": ["-y", "chrome-devtools-mcp@latest"]
}

Key Guidelines

  • Be assertive: Verify claims by checking network requests, DOM, or codebase—then state findings definitively.
  • Verify before recommending: Confirm something is unused before suggesting removal.
  • Quantify impact: Use estimated savings from insights. Don't prioritize changes with 0ms impact.
  • Skip non-issues: If render-blocking resources have 0ms estimated impact, note but don't recommend action.
  • Be specific: Say "compress hero.png (450KB) to WebP" not "optimize images".
  • Prioritize ruthlessly: A site with 200ms LCP and 0 CLS is already excellent—say so.

Read the full file on GitHub · 203 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 1mo ago First seen · 203 lines · 26 tokens per session scan A 4590171d2252

Subscribe to this mod's changes

web-perf is a skill published in the GitHub repository fcakyon/claude-codex-settings (1,181 stars, last pushed yesterday), licensed Apache-2.0. It adds 26 tokens to every session and 2,057 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 83% identical to web-perf, differing in 1 line, and is treated as a copy.

Related

Other skills, from other repositories