Shopify Performance Auditor

A diagnostic script that crawls Shopify storefronts and flags CLS issues, render blocking scripts, uncompressed assets, and mobile funnel leaks killing your conversion rate. Built for growth engineers who need data before they touch code.

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The Problem This Solves

Most developers guess where a store is slow. They install a speed app, run one Lighthouse test, and call it done. Real performance engineering starts with systematic diagnosis. This auditor crawls your entire storefront, maps every bottleneck, and outputs a prioritized fix list with the exact file causing each issue.

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Architecture

graph TD
    A[Input Store URL] --> B[Crawl Storefront Pages]
    B --> C[Run Lighthouse Audit]
    C --> D{Analyze Results}
    D --> E[Flag CLS Issues]
    D --> F[Flag Render Blocking Scripts]
    D --> G[Flag Uncompressed Assets]
    D --> H[Flag Mobile Funnel Leaks]
    E & F & G & H --> I[Generate Priority Report]
    I --> J[Output JSON + HTML Report]

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Audit Checks

Check	Description	Impact
Cumulative Layout Shift	Detects elements causing page jumps	High
Render Blocking Scripts	Flags JS blocking page paint	High
Uncompressed Images	Finds oversized image assets	Medium
Mobile PageSpeed	Full mobile Lighthouse score	High
Third Party Scripts	Maps external script overhead	Medium
Time to First Byte	Server response speed check	High
Largest Contentful Paint	Hero image and font load time	High

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Sample Audit Output

{
  "store": "example-store.myshopify.com",
  "audit_date": "2026-05-31",
  "mobile_score": 42,
  "desktop_score": 71,
  "issues": [
    {
      "type": "render_blocking",
      "severity": "high",
      "file": "app.js",
      "recommendation": "Add defer attribute to script tag"
    },
    {
      "type": "cls",
      "severity": "high",
      "element": ".product-image",
      "recommendation": "Add explicit width and height attributes"
    },
    {
      "type": "uncompressed_image",
      "severity": "medium",
      "file": "hero-banner.jpg",
      "size_kb": 2400,
      "recommendation": "Convert to WebP and compress below 200kb"
    }
  ]
}

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Quick Start

git clone https://github.com/Waynelynx12/shopify-performance-auditor.git
cd shopify-performance-auditor
npm install
cp .env.example .env
node src/audit.js --url https://your-store.myshopify.com

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Environment Variables

Variable	Description
STORE_URL	Target Shopify store URL
OUTPUT_FORMAT	json or html
MOBILE_ONLY	true to run mobile audit only

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Built By

Sheriff Wayne, Growth Engineer and Shopify Technical Specialist. I run systematic performance audits on Shopify stores before touching a single line of code. Data first. Fix second.