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Nitrogen

SEO Audit Checklist

SEO Audit Checklist

Section titled “SEO Audit Checklist”

A quarterly review to catch regressions and ensure best practices. Schedule quarterly in calendar; expect 4-6 hours for a thorough audit on a Nitrogen-sized site.

Section 1: Technical SEO

Section titled “Section 1: Technical SEO”

Crawlability

Section titled “Crawlability”
  • robots.txt valid and accessible at /robots.txt
  • robots.txt doesn’t block important pages (test in Search Console robots tester)
  • Sitemap.xml valid, accessible, submitted to Search Console
  • Sitemap referenced in robots.txt
  • Sitemap “Last read” in Search Console is recent (within last 7 days)
  • Indexed URL count in Search Console roughly matches expected count
  • All important pages indexed (spot-check 20 critical URLs via URL Inspection)
  • No orphaned pages (Screaming Frog crawl → “Orphan Pages” report empty)
  • HTTPS on every URL, no mixed content warnings
  • Trailing slash convention consistent site-wide
  • Canonical URL on every page (self-referential)
  • 404 page custom, returns proper 404 status (NOT soft 404 — test with curl)
  • No redirect chains (max 1 hop — audit with curl bulk script)
  • No redirect loops

Status codes

Section titled “Status codes”
  • Search Console Crawl Stats shows >95% 200 responses
  • 5xx rate <0.5%
  • 404 rate <2%, and remaining 404s are mostly bot probes (not legitimate user traffic)
  • No soft 404s (Search Console Coverage)

On-page SEO

Section titled “On-page SEO”
  • Unique title on every page (Screaming Frog: filter duplicates)
  • Title length 50-60 chars (Screaming Frog: filter outside range)
  • Unique meta description on every page
  • Description length 150-160 chars
  • Exactly one H1 per page (Screaming Frog: H1 audit)
  • Heading hierarchy logical (no skipped levels)
  • Alt text on all content images (Screaming Frog: Images → “Missing Alt Text”)
  • Internal linking from new content to related pages
  • Anchor text descriptive (no “click here”, “read more”)

Structured data

Section titled “Structured data”
  • Organization schema on every page (in layout)
  • BreadcrumbList on deep pages
  • Article schema on blog posts
  • FAQPage schema on FAQ pages
  • Rich Results Test passes for all schema types
  • Schema Markup Validator passes for all schema types
  • Search Console Enhancements show valid coverage, no errors

Performance (Core Web Vitals)

Section titled “Performance (Core Web Vitals)”
  • Core Web Vitals: “Good” for 75%+ of pages (Search Console field data)
  • PageSpeed Insights score >=90 for key landing pages (mobile)
  • LCP <2.5s for 75%+ of pages
  • INP <200ms for 75%+ of pages
  • CLS <0.1 for 75%+ of pages
  • Lighthouse SEO >=95
  • Lighthouse Accessibility >=95

Mobile

Section titled “Mobile”
  • Search Console Mobile Usability clean (no errors)
  • Touch targets >=48×48px (Lighthouse audit)
  • No horizontal scroll on mobile viewports
  • Font size readable (16px+ body)
  • Mobile-first indexing confirmed in Search Console URL Inspection (crawled-as: Smartphone)

Section 2: International / Multilingual

Section titled “Section 2: International / Multilingual”

(Skip if site is single-language)

  • hreflang annotations on all multilingual pages
  • hreflang bidirectional (every page references back)
  • hreflang self-reference included
  • x-default for unmatched locales
  • No broken hreflang (all destinations return 200)
  • URL structure consistent (subdirectory, ccTLD, or subdomain — same throughout)
  • Search Console International Targeting report clean
  • No Accept-Language auto-redirect (test with various Accept-Language headers)

Section 3: Social

Section titled “Section 3: Social”
  • OpenGraph tags on every page
  • og:image 1200×630 px, <1MB, accessible URL
  • og:type appropriate (website or article)
  • og:locale correct for page language
  • Twitter Card tags on every page
  • LinkedIn Post Inspector preview correct for landing pages
  • Facebook Sharing Debugger preview correct
  • OG image alt text on all content with OG images

Section 4: Analytics / Tracking

Section titled “Section 4: Analytics / Tracking”
  • Google Analytics 4 tracking firing on all pages
  • Consent Mode v2 working (per Skill: Consent Mode v2 Debug)
  • GA4 Key Events marked (form submissions, signups, downloads)
  • LinkedIn Insight Tag Verified status in Campaign Manager (if used)
  • Search Console linked to GA4
  • Spot-check tracking: open page in browser, check Network tab for tracking pings

Section 5: CMS / Backend

Section titled “Section 5: CMS / Backend”
  • Slug change auto-creates 301 redirect (test by changing a draft page’s slug)
  • Archived content properly 410-Gone or redirects (not soft 404)
  • Per-content SEO fields editable in admin (title, description, OG image, robots)
  • Search Console connected for ownership verification (DNS TXT primary)
  • IndexNow notifying Bing on new/updated content (check Bing Webmaster IndexNow report)
  • Sitemap regenerated on content publish (verify lastmod updates)
  • Editor SERP preview widget working in CMS

Section 6: Security & Headers

Section titled “Section 6: Security & Headers”
  • HSTS preload enabled (Strict-Transport-Security: max-age=31536000; includeSubDomains; preload)
  • Security headers A+ on securityheaders.com
  • SSL Labs A+ on ssllabs.com
  • No exposed .git, .env, backup files (curl test common paths)
  • CSP active and complete (per Skill: CSP allow-list)
  • No mixed content warnings in browser console on any page

Section 7: Content Quality

Section titled “Section 7: Content Quality”
  • No duplicate content (Search Console “Duplicate without user-selected canonical” near zero)
  • No thin content (<300 words on important pages) — Screaming Frog Content → Word Count
  • Outdated content identified and refreshed or archived
  • 404 pages from old links redirected to relevant content
  • Search Console queries match content (no mismatched targeting — e.g., ranking for queries unrelated to your business)
  • Top-traffic pages have current data, relevant for searcher intent
  • Blog posts older than 1 year reviewed: still accurate? Still relevant? Update or archive.
Section titled “Section 8: Backlinks”
  • Search Console Links report reviewed (Top linking sites, Top linking text)
  • No suspicious backlink patterns (sudden spike from low-quality domains)
  • Broken inbound links identified and 301-redirected to relevant content
  • No need for Disavow (toxic backlinks not present in volume)

Section 9: User Experience

Section titled “Section 9: User Experience”
  • Mobile site matches desktop content (mobile-first indexing requirement)
  • No intrusive interstitials (Google’s Page Experience signal)
  • Cookie banner doesn’t block content above the fold significantly
  • Search Console “Page Experience” shows mostly “Good” pages

Tools to run

Section titled “Tools to run”

Bookmark these and use them for each audit:

Audit deliverable

Section titled “Audit deliverable”

Document findings for each section:

  • ✅ Items that passed
  • ⚠️ Items with warnings (note them, plan for next quarter)
  • ❌ Items that failed (create tickets for fixes)

Include:

  • Search Console data snapshot (impressions, clicks, average position for the quarter)
  • Top issues to address
  • Action items with owners and deadlines
  • Comparison to previous quarter (trends)

The audit document becomes the working plan for the next quarter’s SEO work.

Cross-references

Section titled “Cross-references”
  • Google Search Console — primary tool
  • SEO Glossary — terms used in this checklist
  • All Frontend and Backend SEO topics — each item links to the relevant deep-dive page