Technical SEO Checker

This skill performs comprehensive technical SEO audits to identify issues that may prevent search engines from properly crawling, indexing, and ranking your site.

When to Use This Skill

Launching a new website
Diagnosing ranking drops
Pre-migration SEO audits
Regular technical health checks
Identifying crawl and index issues
Improving site performance
Fixing Core Web Vitals issues

What This Skill Does

Crawlability Audit: Checks robots.txt, sitemaps, crawl issues
Indexability Review: Analyzes index status and blockers
Site Speed Analysis: Evaluates Core Web Vitals and performance
Mobile-Friendliness: Checks mobile optimization
Security Check: Reviews HTTPS and security headers
Structured Data Audit: Validates schema markup
URL Structure Analysis: Reviews URL patterns and redirects
International SEO: Checks hreflang and localization

How to Use

Full Technical Audit

Perform a technical SEO audit for [URL/domain]

Specific Issue Check

Check Core Web Vitals for [URL]

Audit crawlability and indexability for [domain]

Pre-Migration Audit

Technical SEO checklist for migrating [old domain] to [new domain]

Data Sources

See CONNECTORS.md for tool category placeholders.

With ~~web crawler + ~~page speed tool + ~~CDN connected: Claude can automatically crawl the entire site structure via ~~web crawler, pull Core Web Vitals and performance metrics from ~~page speed tool, analyze caching headers from ~~CDN, and fetch mobile-friendliness data. This enables comprehensive automated technical audits.

With manual data only: Ask the user to provide:

Site URL(s) to audit
PageSpeed Insights screenshots or reports
robots.txt file content
sitemap.xml URL or file

Proceed with the full audit using provided data. Note in the output which findings are from automated crawl vs. manual review.

Instructions

When a user requests a technical SEO audit:

Audit Crawlability

## Crawlability Analysis

### Robots.txt Review

**URL**: [domain]/robots.txt
**Status**: [Found/Not Found/Error]

**Current Content**:

[robots.txt content]


| Check | Status | Notes |
|-------|--------|-------|
| File exists | ✅/❌ | [notes] |
| Valid syntax | ✅/⚠️/❌ | [errors found] |
| Sitemap declared | ✅/❌ | [sitemap URL] |
| Important pages blocked | ✅/⚠️/❌ | [blocked paths] |
| Assets blocked | ✅/⚠️/❌ | [CSS/JS blocked?] |
| Correct user-agents | ✅/⚠️/❌ | [notes] |

**Issues Found**:
- [Issue 1]
- [Issue 2]

**Recommended robots.txt**:

User-agent: * Allow: / Disallow: /admin/ Disallow: /private/

Sitemap: https://example.com/sitemap.xml


---

### XML Sitemap Review

**Sitemap URL**: [URL]
**Status**: [Found/Not Found/Error]

| Check | Status | Notes |
|-------|--------|-------|
| Sitemap exists | ✅/❌ | [notes] |
| Valid XML format | ✅/⚠️/❌ | [errors] |
| In robots.txt | ✅/❌ | [notes] |
| Submitted to ~~search console | ✅/⚠️/❌ | [notes] |
| URLs count | [X] | [appropriate?] |
| Only indexable URLs | ✅/⚠️/❌ | [notes] |
| Includes priority | ✅/⚠️ | [notes] |
| Includes lastmod | ✅/⚠️ | [accurate?] |

**Issues Found**:
- [Issue 1]

---

### Crawl Budget Analysis

| Factor | Status | Impact |
|--------|--------|--------|
| Crawl errors | [X] errors | [Low/Med/High] |
| Duplicate content | [X] pages | [Low/Med/High] |
| Thin content | [X] pages | [Low/Med/High] |
| Redirect chains | [X] found | [Low/Med/High] |
| Orphan pages | [X] found | [Low/Med/High] |

**Crawlability Score**: [X]/10

Audit Indexability

## Indexability Analysis

### Index Status Overview

| Metric | Count | Notes |
|--------|-------|-------|
| Pages in sitemap | [X] | |
| Pages indexed | [X] | [source: site: search] |
| Index coverage ratio | [X]% | [good if >90%] |

### Index Blockers Check

| Blocker Type | Found | Pages Affected |
|--------------|-------|----------------|
| noindex meta tag | [X] | [list or "none"] |
| noindex X-Robots | [X] | [list or "none"] |
| Robots.txt blocked | [X] | [list or "none"] |
| Canonical to other | [X] | [list or "none"] |
| 4xx/5xx errors | [X] | [list or "none"] |
| Redirect loops | [X] | [list or "none"] |

### Canonical Tags Audit

| Check | Status | Notes |
|-------|--------|-------|
| Canonicals present | ✅/⚠️/❌ | [X]% of pages |
| Self-referencing | ✅/⚠️/❌ | [notes] |
| Consistent (HTTP/HTTPS) | ✅/⚠️/❌ | [notes] |
| Consistent (www/non-www) | ✅/⚠️/❌ | [notes] |
| No conflicting signals | ✅/⚠️/❌ | [notes] |

### Duplicate Content Issues

| Issue Type | Count | Examples |
|------------|-------|----------|
| Exact duplicates | [X] | [URLs] |
| Near duplicates | [X] | [URLs] |
| Parameter duplicates | [X] | [URLs] |
| WWW/non-WWW | [X] | [notes] |
| HTTP/HTTPS | [X] | [notes] |

**Indexability Score**: [X]/10

Audit Site Speed & Core Web Vitals

## Performance Analysis

### Core Web Vitals

| Metric | Mobile | Desktop | Target | Status |
|--------|--------|---------|--------|--------|
| LCP (Largest Contentful Paint) | [X]s | [X]s | <2.5s | ✅/⚠️/❌ |
| FID (First Input Delay) | [X]ms | [X]ms | <100ms | ✅/⚠️/❌ |
| CLS (Cumulative Layout Shift) | [X] | [X] | <0.1 | ✅/⚠️/❌ |
| INP (Interaction to Next Paint) | [X]ms | [X]ms | <200ms | ✅/⚠️/❌ |

### Additional Performance Metrics

| Metric | Value | Status |
|--------|-------|--------|
| Time to First Byte (TTFB) | [X]ms | ✅/⚠️/❌ |
| First Contentful Paint (FCP) | [X]s | ✅/⚠️/❌ |
| Speed Index | [X] | ✅/⚠️/❌ |
| Total Blocking Time | [X]ms | ✅/⚠️/❌ |
| Page Size | [X]MB | ✅/⚠️/❌ |
| Requests | [X] | ✅/⚠️/❌ |

### Performance Issues

**LCP Issues**:
- [Issue]: [Impact] - [Solution]
- [Issue]: [Impact] - [Solution]

**CLS Issues**:
- [Issue]: [Impact] - [Solution]

**Resource Loading**:
| Resource Type | Count | Size | Issues |
|---------------|-------|------|--------|
| Images | [X] | [X]MB | [notes] |
| JavaScript | [X] | [X]MB | [notes] |
| CSS | [X] | [X]KB | [notes] |
| Fonts | [X] | [X]KB | [notes] |

### Optimization Recommendations

**High Impact**:
1. [Recommendation] - Est. improvement: [X]s
2. [Recommendation] - Est. improvement: [X]s

**Medium Impact**:
1. [Recommendation]
2. [Recommendation]

**Performance Score**: [X]/10

Audit Mobile-Friendliness

## Mobile Optimization Analysis

### Mobile-Friendly Test

| Check | Status | Notes |
|-------|--------|-------|
| Mobile-friendly overall | ✅/❌ | [notes] |
| Viewport configured | ✅/❌ | [viewport tag] |
| Text readable | ✅/⚠️/❌ | Font size: [X]px |
| Tap targets sized | ✅/⚠️/❌ | [notes] |
| Content fits viewport | ✅/❌ | [notes] |
| No horizontal scroll | ✅/❌ | [notes] |

### Responsive Design Check

| Element | Desktop | Mobile | Issues |
|---------|---------|--------|--------|
| Navigation | [status] | [status] | [notes] |
| Images | [status] | [status] | [notes] |
| Forms | [status] | [status] | [notes] |
| Tables | [status] | [status] | [notes] |
| Videos | [status] | [status] | [notes] |

### Mobile-First Indexing

| Check | Status | Notes |
|-------|--------|-------|
| Mobile version has all content | ✅/⚠️/❌ | [notes] |
| Mobile has same structured data | ✅/⚠️/❌ | [notes] |
| Mobile has same meta tags | ✅/⚠️/❌ | [notes] |
| Mobile images have alt text | ✅/⚠️/❌ | [notes] |

**Mobile Score**: [X]/10

Audit Security & HTTPS

## Security Analysis

### HTTPS Status

| Check | Status | Notes |
|-------|--------|-------|
| SSL certificate valid | ✅/❌ | Expires: [date] |
| HTTPS enforced | ✅/❌ | [redirects properly?] |
| Mixed content | ✅/⚠️/❌ | [X] issues |
| HSTS enabled | ✅/⚠️ | [notes] |
| Certificate chain | ✅/⚠️/❌ | [notes] |

### Security Headers

| Header | Present | Value | Recommended |
|--------|---------|-------|-------------|
| Content-Security-Policy | ✅/❌ | [value] | [recommendation] |
| X-Frame-Options | ✅/❌ | [value] | DENY or SAMEORIGIN |
| X-Content-Type-Options | ✅/❌ | [value] | nosniff |
| X-XSS-Protection | ✅/❌ | [value] | 1; mode=block |
| Referrer-Policy | ✅/❌ | [value] | [recommendation] |

**Security Score**: [X]/10

Audit URL Structure

## URL Structure Analysis

### URL Pattern Review

| Check | Status | Notes |
|-------|--------|-------|
| HTTPS URLs | ✅/⚠️/❌ | [X]% HTTPS |
| Lowercase URLs | ✅/⚠️/❌ | [notes] |
| No special characters | ✅/⚠️/❌ | [notes] |
| Readable/descriptive | ✅/⚠️/❌ | [notes] |
| Appropriate length | ✅/⚠️/❌ | Avg: [X] chars |
| Keywords in URLs | ✅/⚠️/❌ | [notes] |
| Consistent structure | ✅/⚠️/❌ | [notes] |

### URL Issues Found

| Issue Type | Count | Examples |
|------------|-------|----------|
| Dynamic parameters | [X] | [URLs] |
| Session IDs in URLs | [X] | [URLs] |
| Uppercase characters | [X] | [URLs] |
| Special characters | [X] | [URLs] |
| Very long URLs (>100) | [X] | [URLs] |

### Redirect Analysis

| Check | Status | Notes |
|-------|--------|-------|
| Redirect chains | [X] found | [max chain length] |
| Redirect loops | [X] found | [URLs] |
| 302 → 301 needed | [X] found | [URLs] |
| Broken redirects | [X] found | [URLs] |

**URL Score**: [X]/10

Audit Structured Data

CORE-EEAT alignment: Schema markup quality maps to O05 (Schema Markup) in the CORE-EEAT benchmark. See content-quality-auditor for full content quality audit.

## Structured Data Analysis

### Schema Markup Found

| Schema Type | Pages | Valid | Errors |
|-------------|-------|-------|--------|
| [Type 1] | [X] | ✅/❌ | [errors] |
| [Type 2] | [X] | ✅/❌ | [errors] |

### Validation Results

**Errors**:
- [Error 1]: [affected pages] - [solution]
- [Error 2]: [affected pages] - [solution]

**Warnings**:
- [Warning 1]: [notes]

### Missing Schema Opportunities

| Page Type | Current Schema | Recommended |
|-----------|----------------|-------------|
| Blog posts | [current] | Article + FAQ |
| Products | [current] | Product + Review |
| Homepage | [current] | Organization |

**Structured Data Score**: [X]/10

Audit International SEO (if applicable)

## International SEO Analysis

### Hreflang Implementation

| Check | Status | Notes |
|-------|--------|-------|
| Hreflang tags present | ✅/❌ | [notes] |
| Self-referencing | ✅/⚠️/❌ | [notes] |
| Return tags present | ✅/⚠️/❌ | [notes] |
| Valid language codes | ✅/⚠️/❌ | [notes] |
| x-default tag | ✅/⚠️ | [notes] |

### Language/Region Targeting

| Language | URL | Hreflang | Status |
|----------|-----|----------|--------|
| [en-US] | [URL] | [tag] | ✅/⚠️/❌ |
| [es-ES] | [URL] | [tag] | ✅/⚠️/❌ |

**International Score**: [X]/10

Generate Technical Audit Summary

# Technical SEO Audit Report

**Domain**: [domain]
**Audit Date**: [date]
**Pages Analyzed**: [X]

## Overall Technical Health: [X]/100

Score Breakdown: ████████░░ Crawlability: 8/10 ███████░░░ Indexability: 7/10 █████░░░░░ Performance: 5/10 ████████░░ Mobile: 8/10 █████████░ Security: 9/10 ██████░░░░ URL Structure: 6/10 █████░░░░░ Structured Data: 5/10


## Critical Issues (Fix Immediately)

1. **[Issue]**: [Impact] 
   - Affected: [pages/scope]
   - Solution: [specific fix]
   - Priority: 🔴 Critical

2. **[Issue]**: [Impact]
   - Affected: [pages/scope]
   - Solution: [specific fix]
   - Priority: 🔴 Critical

## High Priority Issues

1. **[Issue]**: [Solution]
2. **[Issue]**: [Solution]

## Medium Priority Issues

1. **[Issue]**: [Solution]
2. **[Issue]**: [Solution]

## Quick Wins

These can be fixed quickly for immediate improvement:

1. [Quick fix 1]
2. [Quick fix 2]
3. [Quick fix 3]

## Implementation Roadmap

### Week 1: Critical Fixes
- [ ] [Task 1]
- [ ] [Task 2]

### Week 2-3: High Priority
- [ ] [Task 1]
- [ ] [Task 2]

### Week 4+: Optimization
- [ ] [Task 1]
- [ ] [Task 2]

## Monitoring Recommendations

Set up alerts for:
- Core Web Vitals drops
- Crawl error spikes
- Index coverage changes
- Security issues

Validation Checkpoints

Input Validation

Site URL or domain clearly specified
Access to technical data (robots.txt, sitemap, or crawl results)
Performance metrics available (via ~~page speed tool or screenshots)

Output Validation

Every recommendation cites specific data points (not generic advice)
All issues include affected URLs or page counts
Performance metrics include actual numbers with units (seconds, KB, etc.)
Source of each data point clearly stated (~~web crawler data, ~~page speed tool, user-provided, or estimated)

Example

User: "Check the technical SEO of cloudhosting.com"

Output:

# Technical SEO Audit Report

**Domain**: cloudhosting.com
**Audit Date**: 2024-09-15
**Pages Analyzed**: 312

## Crawlability Analysis

### Robots.txt Review

**URL**: cloudhosting.com/robots.txt
**Status**: Found

| Check | Status | Notes |
|-------|--------|-------|
| File exists | ✅ | 200 response |
| Valid syntax | ⚠️ | Wildcard pattern `Disallow: /*?` too aggressive — blocks faceted pages |
| Sitemap declared | ❌ | No Sitemap directive in robots.txt |
| Important pages blocked | ⚠️ | /pricing/ blocked by `Disallow: /pricing` rule |
| Assets blocked | ✅ | CSS/JS accessible |

**Issues Found**:
- Sitemap URL not declared in robots.txt
- `/pricing/` inadvertently blocked — high-value commercial page

### XML Sitemap Review

**Sitemap URL**: cloudhosting.com/sitemap.xml
**Status**: Found (not referenced in robots.txt)

| Check | Status | Notes |
|-------|--------|-------|
| Sitemap exists | ✅ | Valid XML, 287 URLs |
| Only indexable URLs | ❌ | 23 noindex URLs included |
| Includes lastmod | ⚠️ | All dates set to 2023-01-01 — not accurate |

**Crawlability Score**: 5/10

## Performance Analysis

### Core Web Vitals

| Metric | Mobile | Desktop | Target | Status |
|--------|--------|---------|--------|--------|
| LCP (Largest Contentful Paint) | 4.8s | 2.1s | <2.5s | ❌ Mobile / ✅ Desktop |
| FID (First Input Delay) | 45ms | 12ms | <100ms | ✅ / ✅ |
| CLS (Cumulative Layout Shift) | 0.24 | 0.08 | <0.1 | ❌ Mobile / ✅ Desktop |
| INP (Interaction to Next Paint) | 380ms | 140ms | <200ms | ❌ Mobile / ✅ Desktop |

### Additional Performance Metrics

| Metric | Value | Status |
|--------|-------|--------|
| Time to First Byte (TTFB) | 1,240ms | ❌ |
| Page Size | 3.8MB | ❌ |
| Requests | 94 | ⚠️ |

**LCP Issues**:
- Uncompressed hero image (2.4MB PNG): Convert to WebP, est. save 1.9MB
- No CDN detected: TTFB 1,240ms from origin server

**CLS Issues**:
- Ad banner at top of page injects without reserved height (0.18 shift contribution)

**Performance Score**: 3/10

## Security Analysis

### HTTPS Status

| Check | Status | Notes |
|-------|--------|-------|
| SSL certificate valid | ✅ | Expires: 2025-03-22 |
| HTTPS enforced | ⚠️ | http://cloudhosting.com returns 200 instead of 301 redirect |
| Mixed content | ❌ | 7 images loaded over HTTP on /features/ page |
| HSTS enabled | ❌ | Header not present |

**Security Score**: 5/10

## Structured Data Analysis

### Schema Markup Found

| Schema Type | Pages | Valid | Errors |
|-------------|-------|-------|--------|
| Organization | 1 (homepage) | ✅ | None |
| Article | 0 | — | Missing on 48 blog posts |
| Product | 0 | — | Missing on 5 plan pages |
| FAQ | 0 | — | Missing on 12 pages with FAQ content |

**Structured Data Score**: 3/10

## Overall Technical Health: 42/100

Score Breakdown: █████░░░░░ Crawlability: 5/10 ██████░░░░ Indexability: 6/10 ███░░░░░░░ Performance: 3/10 ██████░░░░ Mobile: 6/10 █████░░░░░ Security: 5/10 ██████░░░░ URL Structure: 6/10 ███░░░░░░░ Structured Data: 3/10


## Priority Issues

### 🔴 Critical (Fix Immediately)
1. **Mobile LCP 4.8s (target <2.5s)** — Compress hero image to WebP (est. save 1.9MB) and implement a CDN to reduce TTFB from 1,240ms to <400ms.

### 🟡 Important (Fix Soon)
2. **HTTP not redirecting to HTTPS** — Add 301 redirect from http:// to https:// and enable HSTS header. 7 mixed-content images on /features/ need URL updates.

### 🟢 Minor (Optimize)
3. **No Article/FAQ schema on blog posts** — Add Article schema to 48 blog posts and FAQ schema to 12 FAQ pages for rich result eligibility.

Technical SEO Checklist

### Crawlability
- [ ] robots.txt is valid and not blocking important content
- [ ] XML sitemap exists and is submitted to ~~search console
- [ ] No crawl errors in ~~search console
- [ ] No redirect chains or loops

### Indexability  
- [ ] Important pages are indexable
- [ ] Canonical tags are correct
- [ ] No duplicate content issues
- [ ] Pagination is handled correctly

### Performance
- [ ] Core Web Vitals pass
- [ ] Page speed under 3 seconds
- [ ] Images are optimized
- [ ] JS/CSS are minified

### Mobile
- [ ] Mobile-friendly test passes
- [ ] Viewport is configured
- [ ] Touch elements are properly sized

### Security
- [ ] HTTPS is enforced
- [ ] SSL certificate is valid
- [ ] No mixed content
- [ ] Security headers present

### Structure
- [ ] URLs are clean and descriptive
- [ ] Site architecture is logical
- [ ] Internal linking is strong

Tips for Success

Prioritize by impact - Fix critical issues first
Monitor continuously - Use ~~search console alerts
Test changes - Verify fixes work before deploying widely
Document everything - Track changes for troubleshooting
Regular audits - Schedule quarterly technical reviews

Technical SEO Severity Framework

Issue Classification

Severity	Impact Description	Examples	Response Time
Critical	Prevents indexation or causes site-wide issues	Robots.txt blocking site, noindex on key pages, site-wide 500 errors	Same day
High	Significantly impacts rankings or user experience	Slow page speed, missing hreflang, duplicate content, redirect chains	Within 1 week
Medium	Affects specific pages or has moderate impact	Missing schema, suboptimal canonicals, thin content pages	Within 1 month
Low	Minor optimization opportunities	Image compression, minor CLS issues, non-essential schema missing	Next quarter

Technical Debt Prioritization Matrix

Factor	Weight	Assessment
Pages affected	30%	Site-wide > Section > Single page
Revenue impact	25%	Revenue pages > Blog > Utility pages
Fix difficulty	20%	Config change < Template change < Code rewrite
Competitive impact	15%	Competitors passing you > parity > you ahead
Crawl budget waste	10%	High waste > Moderate > Minimal

Core Web Vitals Optimization Quick Reference

LCP (Largest Contentful Paint) Optimization

Root Cause	Detection	Fix
Large hero image	PageSpeed Insights	Serve WebP, resize to container, add loading="lazy"
Render-blocking CSS/JS	DevTools Coverage	Defer non-critical, inline critical CSS
Slow server response	TTFB >800ms	CDN, server-side caching, upgrade hosting
Third-party scripts	DevTools Network	Defer/async, use facade pattern

CLS (Cumulative Layout Shift) Optimization

Root Cause	Detection	Fix
Images without dimensions	DevTools	Add explicit width/height attributes
Ads/embeds without reserved space	Visual inspection	Set min-height on containers
Web fonts causing FOUT	DevTools	font-display: swap + preload fonts
Dynamic content injection	Visual inspection	Reserve space with CSS

INP (Interaction to Next Paint) Optimization

Root Cause	Detection	Fix
Long JavaScript tasks	DevTools Performance	Break into smaller tasks, use requestIdleCallback
Heavy event handlers	DevTools	Debounce/throttle, use passive listeners
Main thread blocking	DevTools	Web workers for heavy computation

Reference Materials

robots.txt Reference - Syntax guide, templates, common configurations
HTTP Status Codes - SEO impact of each status code, redirect best practices

Related Skills

on-page-seo-auditor — On-page SEO audit
schema-markup-generator — Fix schema issues
performance-reporter — Monitor improvements
internal-linking-optimizer — Fix link issues
alert-manager — Set up alerts for technical issues found
content-quality-auditor — Full 80-item CORE-EEAT audit

technical-seo-checker