Audit Pillars — Complete Reference

All 24 SEO audit pillars evaluated by SEO CodeBase Auditor. Each pillar includes its scope, key checks, and which project types it applies to.

Pillar Overview

#	Pillar	Applies To
1	On-Page SEO	All sites
2	Technical SEO	All sites
3	Performance SEO (Core Web Vitals)	All sites
4	URL Structure & Site Architecture	All sites
5	Mobile SEO	All sites
6	Image SEO	All sites
7	Semantic SEO & Content Optimization	Content-heavy sites
8	Internal Linking & Link Equity	All sites
9	XML Sitemap & Robots.txt	All sites
10	Social & Regional SEO	All sites
11	Security SEO	All sites
12	Accessibility (a11y) SEO	All sites
13	E-Commerce SEO	E-commerce only
14	Blog & Content SEO	Blog/content sites
15	JavaScript Framework SEO	Framework-detected sites
16	E-E-A-T Signals	Content-heavy, YMYL sites
17	Rich Results Eligibility	All sites
18	AI / SGE / LLM / Voice Search	All sites
19	CI/CD & Automation	All sites
20	Migration SEO	Sites undergoing migration
21	Content Pruning & Consolidation	Sites with 50+ pages
22	Third-Party Script Audit	All sites
23	Competitor SEO Analysis	All sites (requires competitor URLs)
24	Video & YouTube SEO	Sites with video embeds

Pillar 1: On-Page SEO All Sites

Scope: Title tags, meta descriptions, heading hierarchy, anchor mechanics, viewport, charset, language, keyword cannibalization, CTR optimization, SERP snippet quality, structured content, table optimization, external links, keyword placement scoring.

Key Checks

Title tag existence, 50-60 char length, front-loaded primary keyword, brand suffix, uniqueness
Missing title tag detection (Critical finding)
Short title tag remediation (<40 chars)
Meta description existence, 150-160 char length, actionable copywriting, keyword inclusion
Meta description A/B testing framework
Exactly one <h1> per page, sequential heading nesting (h2→h3→h4)
Non-descriptive anchor text ("click here", "read more")
Viewport meta tag: width=device-width, initial-scale=1
Charset: <meta charset="utf-8"> as first meta tag
Language attribute: <html lang="...">
Title & H1 alignment (identical = thin content signal)
Cross-page keyword cannibalization
CTR optimization: power words, emotional triggers, numbers in titles
SERP snippet quality: truncation risk, brand inclusion, CTA language
Structured content layout: bullet lists, bolding, short paragraphs
Table optimization for featured snippet eligibility
External link quality: relevance, authority, rel="noopener noreferrer"
Keyword placement scoring across 5 zones: title, H1, URL slug, first paragraph, H2

Keyword Placement Score

Score	Rating
5/5	Optimal
3-4/5	Needs improvement
<3/5	Critical keyword placement gap

Pillar 2: Technical SEO All Sites

Scope: Indexability matrix, crawl budget, structured data, canonical routing, robots meta, staging detection, robots.txt, JavaScript SEO, render-blocking, HTML5 semantics, deprecated HTML, HTTP status codes, soft 404s, redirect loops, broken links, parameterized URLs, duplicate pages/metadata, infinite crawl traps, compression, caching, CDN, server response patterns.

Key Checks

Indexability Matrix: For every URL: indexable / non-indexable / conflicting directives / blocked
Crawl Budget Assessment: Wasted crawl on parameters, infinite spaces, low-value pages
Structured Data Ecosystem: JSON-LD validation, missing types by project
Canonical Routing: Correct preferred URL, no trailing/protocol/www mismatches
Staging/Dev Detection: Publicly accessible staging URLs, leaked canonical/OG references
Robots.txt Deep Audit: User-agent, Disallow, Allow, Sitemap, Crawl-delay
JavaScript SEO: CSR detection, SSR/SSG fallback recommendations
Render-Blocking Resources: CSS/JS in <head> without defer/async
HTML5 Semantic Structure: <header>, <nav>, <main>, <article>, <section>
Deprecated HTML: <font>, <center>, <marquee>, bgcolor, align
HTTP Status Code Inventory: 200 on error pages, 302→301, 5xx, missing 404s
Soft 404 Detection: 200 status with thin/404 messaging content
Redirect Loop Detection: A→B→A loops, chains >3 hops
Broken Links: Internal href verification against file system
Duplicate Pages: WWW vs non-www, trailing slash, HTTP vs HTTPS, parameters
Compression: gzip/brotli on HTML, CSS, JS, JSON, SVG, fonts
CDN Analysis: Cloudflare, Akamai, Fastly, CloudFront detection
Server Response: TTFB >500ms flagging, Server-Timing API

Pillar 3: Performance SEO (Core Web Vitals) All Sites

Scope: LCP, FCP, CLS, INP, TTFB, image optimization, CSS/JS minification, preconnect/preload/prefetch, font loading, unused CSS/JS, DOM size, mobile vs desktop splits, CWV priority scoring.

Core Web Vital Thresholds

Metric	Good	Needs Improvement	Poor
LCP	≤2.5s	2.5-4.0s	>4.0s
FCP	≤1.8s	1.8-3.0s	>3.0s
CLS	≤0.1	0.1-0.25	>0.25
INP	≤200ms	200-500ms	>500ms
TTFB	≤800ms	800-1800ms	>1800ms

Key Checks

LCP candidate image: no loading="lazy", explicit width/height, preload with <link rel="preload">
FCP: render-blocking CSS/JS, font-display strategy
CLS: explicit dimensions on all images/iframes/embeds, reserved ad slots, font-display: swap
INP: DOM size >1500 nodes, inline event handlers, long tasks >50ms
TTFB: DNS, TLS, redirect chains, server processing
Image below fold: loading="lazy", WebP/AVIF format, compression
CSS/JS minification, bundling opportunities
Preconnect for critical third-party origins
Font loading: font-display: swap, WOFF2, subset strategy
DOM complexity: >1500 nodes, >30 nesting levels

Pillar 4: URL Structure & Site Architecture All Sites

Scope: URL hierarchy, length, slugs, trailing slashes, WWW consistency, protocol, pagination, silo architecture, orphan pages, redirect chains.

Key Checks

Logical hierarchy: /category/product not /p?id=123
URL length flag: >75-100 characters
Kebab-case slugs with target keywords, no underscores
Slug Quality: keyword inclusion, stop word bloat, meaningfulness, length >5 words
Trailing slash consistency
WWW vs non-WWW canonical consistency
HTTPS protocol enforcement
Pagination: rel="next"/rel="prev" or view-all canonical
Silo architecture: topical clustering and interlinking
Orphan pages: files not linked from any page
http-equiv="refresh" redirect flagging

Pillar 5: Mobile SEO All Sites

Scope: Viewport configuration, responsive design, touch targets, font size, mobile structured data, interstitials.

Key Checks

Viewport: width=device-width, initial-scale=1 — no user-scalable=no
Responsive CSS: media queries or responsive framework
Touch targets: ≥48×48 CSS pixels, ≥8px gap
Font size: ≥16px body text (iOS zoom prevention)
Structured data mobile rendering
Full-screen overlay / intrusive interstitial detection

Pillar 6: Image SEO All Sites

Scope: Alt text, format, dimensions, responsive images, image sitemap, file names, lazy loading.

Key Checks

Alt text: empty, missing, or purely decorative flagging
Format: legacy (GIF, BMP, TIFF) → WebP/AVIF recommendation
Explicit width and height on all <img> tags
<picture> or srcset for large hero images
Image sitemap recommendation (>10 meaningful images)
Descriptive, hyphenated file names (flag IMG_001.jpg)
loading="lazy" below fold, no lazy on LCP candidates

Pillar 7: Semantic SEO & Content Optimization Content-Heavy

Scope: Search intent mapping, query intent, keyword cannibalization, content depth, readability, keyword stuffing/density, semantic relationships, entity coverage, knowledge graph alignment, topical gaps, topic clustering, passage optimization, taxonomy quality, information gain, NLP readiness, content completeness, freshness, anchor text diversity.

Key Checks

Intent mapping: informational, navigational, transactional, commercial, comparison, how-to, definitional
Content depth thresholds: general 300w, e-commerce category 100w, blog 200w
Readability: Flesch-Kincaid grade 8-10, Gunning Fog 12-14
Keyword density: >3% = stuffing risk, <0.5% = insufficient relevance
Semantic co-occurrence gaps (e.g., "vegan recipe" should include "plant-based", "dairy-free")
Entity density: <3 entities per 100 words = insufficient
Knowledge Graph alignment: use Google's entity labels
Topical completeness score: 0-100% rubric
Passage optimization: standalone ranking potential per section
Information gain: flag pages with >70% content overlap
Content freshness: datePublished/dateModified signals

Pillar 8: Internal Linking & Link Equity All Sites

Scope: Orphan pages, link depth, broken links, nofollow abuse, navigation structure, footer links, breadcrumbs, link equity silos.

Key Checks

Orphan pages: zero internal links pointing to them
Link depth: >3 clicks from home page for important content
Broken internal links: href verification against file system
Unnecessary rel="nofollow" on internal links
<nav> semantic element for main navigation
Footer links: important pages included, not just legal
BreadcrumbList schema: <ol> with itemscope/itemtype
Hub-and-spoke link equity distribution

Pillar 9: XML Sitemap & Robots.txt All Sites

Scope: Robots.txt existence/directives, sitemap structure/coverage, sitemap index, image/video sitemaps, IndexNow protocol, sitemap URL inventory analysis.

Key Checks

Robots.txt: User-agent, Disallow, Allow, Sitemap, Crawl-delay validation
Sitemap existence: namespace, <lastmod>, <changefreq>, <priority>
Sitemap coverage: all indexable pages listed, non-indexable excluded
Sitemap URL Inventory: Categorize every URL by type, detect low-value URL inflation, recommend cleanup
Sitemap index for >50k URLs
Image/video sitemap extensions when relevant

IndexNow Protocol

POST https://api.indexnow.org/IndexNow
Content-Type: application/json

{
  "host": "www.example.com",
  "key": "<your-key>",
  "keyLocation": "https://www.example.com/<key>.txt",
  "urlList": ["https://www.example.com/page1"]
}

Response codes: 200 (success), 400 (invalid), 403 (key invalid), 422 (URL mismatch), 429 (rate limited)

Pillar 10: Social & Regional SEO All Sites

Scope: Open Graph, Twitter Cards, OG/Twitter quality, Local Business schema, NAP consistency, hreflang, geo-targeting, social share buttons.

OG/Twitter Quality Checks

og:image dimensions: flag <1200×630px or >5MB
og:title vs <title> divergence: flag >50% character difference
twitter:card type: summary vs summary_large_image appropriateness
og:description quality: flag identical to meta description or <50 chars

Regional Checks

LocalBusiness schema: address, telephone, openingHours, geo, areaServed
NAP consistency across all pages
Hreflang: self-referencing, x-default, no contradictory targets
Google Business Profile recommendations

Pillar 11: Security SEO All Sites

Scope: HTTPS enforcement, HSTS, mixed content, form security, external link security.

Key Checks

All internal links, canonicals, OG URLs use https://
Mixed content: http:// resources on https:// pages
Forms: http:// action URLs, missing name attributes
External links without rel="noopener noreferrer"

Pillar 12: Accessibility (a11y) SEO All Sites

Scope: ARIA landmarks, form labels, focus order, color contrast, skip navigation, video accessibility, empty interactive elements, document language.

Key Checks

ARIA landmarks: <header>, <nav>, <main>, <footer>, <aside>
Form labels: <label> or aria-label on all inputs
Focus order: no tabindex >0
Color contrast: WCAG AA 4.5:1 minimum
Skip navigation link as first focusable element
<video> without <track> (captions)
Empty <a> or <button> elements
lang attribute matches content language

Pillar 13: E-Commerce SEO E-Commerce Only

Scope: Product/Review schema, availability, pricing, category pages, faceted navigation, breadcrumbs, product images.

Key Checks

Product schema: name, description, offers, image, sku, brand, aggregateRating
Review schema: author, reviewRating, itemReviewed
Availability: in_stock, out_of_stock, preorder
Price format: price, priceCurrency
Category page content: <100 words = thin
Faceted navigation: filter/sort URL parameters → noindex
BreadcrumbList schema on product/category pages

Pillar 14: Blog & Content SEO Blog/Content

Scope: Article/Author schema, blog listing, related content, category/tag SEO, reading time, TOC, freshness.

Key Checks

Article schema: headline, author, datePublished, dateModified, publisher, image
Person schema for author bio sections
Paginated blog archive: canonical + prev/next
Related posts with internal links
Category/tag pages: thin/duplicate content → noindex
Reading time indicator
Anchor-linked table of contents for long-form
Posts >1 year without dateModified

Pillar 15: JavaScript Framework SEO Framework-Detected

15a: Next.js / Nuxt / Remix (SSR/SSG/ISR)

Rendering strategy detection (SSR, SSG, ISR, CSR)
getStaticProps vs getServerSideProps audit
ISR revalidate values
Framework-level meta API (generateMetadata, useHead)
next/image / nuxt-img usage
next/link / <NuxtLink> for internal routes
getStaticPaths / dynamic route coverage
Middleware / edge function crawlability

15b: SPA (React / Vue / Svelte / Angular)

CSR detection: content requires JS execution
Hash-based routing (#/route) → non-crawlable
Route-level code splitting, bundle size >500KB
Client-side meta injection (og:image missing from scrapers)
Skeleton/loading state interference with rendering budget

15c: Static Site Generators (Astro / Eleventy / Hugo)

Build output: fully rendered HTML without JS
Partial hydration audit (Astro: client:load vs client:idle vs client:visible)
Content collection frontmatter schema consistency

Pillar 16: E-E-A-T Signals Content/YMYL

Scope: Experience, expertise, authoritativeness, trustworthiness — author attribution, About/Contact pages, trust page reachability, external citations, content credibility, reviews, YMYL compliance, reputation indicators, brand authority.

Two-Layer Trust Page Verification

Exists — Page has substantive content (not placeholder)
Reachable — Linked from navigation or within 2 clicks of homepage

Automated Contact Pathway Detection

Dedicated Contact Page (highest trust)
About Page with Contact Details
Footer Contact Info
Social Media Links Only (lowest — flag for local businesses)

Key Checks

Experience signals: first-person pronouns + action verbs, original photos, dates/specifics
Author bylines: full name, professional photo, credential disclosure, social links
Author schema: Person with name, url, sameAs
About page: entity details, team credentials, expertise signals
Contact page: verifiable address, email, phone
External citations: .gov/.edu, peer-reviewed, industry standards
Content credibility: date-appropriate references, cited sources, claims-to-evidence ratio
Review/testimonial verification: Review schema, third-party platform integration
YMYL compliance: credentials, disclaimers, dateModified within 12 months
Brand consistency across title tags, copyright, schema, OG, NAP

Pillar 17: Rich Results Eligibility All Sites

Scope: Rich result opportunity mapping, required fields validation, publishing entity logo, carousel eligibility.

Rich Result	Schema Required	Key Required Fields
Article	`Article`, `NewsArticle`, `BlogPosting`	headline, image, datePublished, author, publisher.logo
Product	`Product`	name, image, offers.price, offers.availability
Review Snippet	`Review`	itemReviewed, reviewRating.ratingValue, author
Recipe	`Recipe`	name, image, recipeIngredient, recipeInstructions
FAQ	`FAQPage`	mainEntity with Question + AcceptedAnswer
How-To	`HowTo`	name, step with Step + text
Local Business	`LocalBusiness`	name, address, telephone
BreadcrumbList	`BreadcrumbList`	itemListElement with ListItem
Sitelinks Search	`WebSite`	potentialAction + SearchAction
Video	`VideoObject`	name, description, thumbnailUrl, uploadDate
Event	`Event`	name, startDate, location/virtualLocation
Job Posting	`JobPosting`	title, description, datePosted, hiringOrganization
Course	`Course`	name, description, provider
Organization	`Organization`	name, logo (112×112px min), url, sameAs

Pillar 18: AI / SGE / LLM / Voice Search Optimization All Sites

Scope: AI Overview readiness, llms.txt, conversational keywords, definitional content, structured Q&A, entity richness, brand as entity, voice search optimization, featured snippet targeting.

Key Checks

AI Overview extraction: clear, concise answers early in content
llms.txt at root: site summary for LLM discoverability
Conversational long-tail question phrases
Definitional paragraph blocks (first authoritative definition)
FAQPage schema for Q&A content
Entity density: <3 entities per 100 words = insufficient
Brand represented as entity with @id in schema
Voice search: standalone 30-50 word answers to likely queries
Featured snippet formatting: paragraph, list, table snippets
QA fragment structuring: H2/H3 question heading → 1-2 sentence answer → detail

Pillar 19: CI/CD & Automation All Sites

Scope: Pre-commit hooks, GitHub Actions, GitLab CI, Lighthouse CI, HTML proofer, scheduled audits, Slack/email alerts, deploy hooks, A/B SEO testing.

Pre-Commit Hook Checks

HTML validation
Meta tag presence on new/modified HTML
Alt text verification on new images
Internal link validity
Schema syntax validation

GitHub Actions Workflow Triggers

Push/PR to main/staging
Generate seo_audit_report.md as artifact
Comment severity summary on PRs
Fail pipeline on Critical issues

Pillar 20: Migration SEO Migration

Scope: URL mapping, redirect chains, canonical conflicts, protocol migration, domain change checklist, content fidelity, structured data migration, rollback readiness.

Domain Migration Checklist

Update all internal links
Update canonical URLs
Update OG/Twitter URLs
Update sitemap URLs
Update robots.txt Sitemap directive
Google Search Console change of address
Maintain old URL infrastructure 6+ months

Pillar 21: Content Pruning & Consolidation 50+ Pages

Scope: Thin content, duplicate/near-duplicate, orphan content, low-value page types, consolidation strategy, crawl budget recovery, redirect cleanup, content hub restructuring.

Action	When
Merge	Combine with stronger related page, 301 redirect weaker
Rewrite	Expand to minimum viability threshold
Remove	410 Gone or noindex (no link equity)
Noindex	Keep for internal users, remove from index

Pillar 22: Third-Party Script Audit All Sites

Scope: Script inventory, critical path impact, tag manager audit, chat widget impact, ad script impact, analytics, font loading, consent mode, performance budgets.

Key Checks

Render-blocking detection (loaded in <head> without defer/async)
GTM container position (must be in <head>)
Chat widget: synchronous loading, >200KB bundles, CLS from injected nodes
Ad scripts: layout shift without reserved slots, content-delaying load
Third-party consolidation opportunities
Consent Mode v2 async loading
Script waterfall analysis
Performance budget recommendation

Pillar 23: Competitor SEO Analysis All Sites

Scope: Competitor identification, content depth comparison, keyword positioning, semantic coverage, site architecture, internal linking, SERP feature analysis, schema adoption, technical benchmarking, UX patterns.

Output

Competitor	Strengths	Weaknesses	Opportunities
Competitor A	Better entity coverage, richer schema	Slower page speed, weaker internal linking	Add entity coverage, maintain speed advantage

Pillar 24: Video & YouTube SEO Video Sites

Scope: Video content inventory, VideoObject schema, YouTube embed best practices, transcripts/captions, title/description/tag optimization, thumbnails, video sitemaps, channel signals, accessibility, rich result eligibility, performance impact.

Key Checks

VideoObject schema: name, description, thumbnailUrl, uploadDate, duration
YouTube privacy mode: youtube-nocookie.com
loading="lazy" on off-screen video iframes
Explicit width/height on iframes (CLS prevention)
On-page transcripts for indexability
<track kind="captions"> for self-hosted video
Custom thumbnails: 1280×720px with text overlay
Video sitemap for 10+ videos
No autoplay above the fold