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SEO Rule Sources

QuikSEO audit rules cite the documents they rely on: Google Search Central first, then W3C and WHATWG specifications, IETF RFCs and web.dev. This register lists each document with its publisher, the date it was last opened and confirmed, and the rules that cite it, so you can check every rule against its source.

How a Source Gets Into the Register

A document enters the register only after it was opened and found to say what the citing rule checks.

  1. For each rule, the most authoritative document is chosen: Google Search Central, then W3C and WHATWG, IETF RFCs, web.dev, and MDN only when none of them covers the subject.
  2. The document is opened and its statement is compared with what the rule checks.
  3. A second check opens every URL again and removes any source that does not say what is claimed.

The plan's ids S10 to S38 keep their numbers; the other documents have ids starting at Q01. Each entry below has its own anchor, which the rule pages link to.

Sources by Publisher

The register holds 113 documents from 13 publishers, cited by the page rules, the site rules of a crawl and the site contract assertion types.

Google Search Central

IdDocumentCheckedCited by
Q01 How HTTP Status Codes Affect Google's Crawlers 2026-10-07 Page Answers With an Error Status, Redirect Chain, Soft 404, Internal Link to an Error Page
Q04 Build and Submit a Sitemap 2026-10-07 Sitemap Not Declared in robots.txt, Invalid Sitemap, Sitemap URL Not Indexable
Q05 General Structured Data Guidelines 2026-10-07 Structured Data Required Properties Missing
Q06 Breadcrumb (BreadcrumbList) structured data 2026-10-07 Breadcrumb With a Single Item
Q13 Structured Data Markup that Google Search Supports 2026-10-07 Structured Data Required Properties Missing
Q25 Understanding Core Web Vitals and Google search results 2026-10-07 Core Web Vitals Field Data
Q26 Define Website Favicon for Search Results | Google Search Central 2026-10-07 Favicon
Q27 How to Write Meta Descriptions 2026-10-07 Duplicate Meta Description
Q28 Redirects and Google Search | Google Search Central 2026-10-07 Meta Refresh, WWW and Non-WWW Both Serve the Page
Q29 How to specify a canonical URL with rel="canonical" and other methods 2026-10-07 Conflicting Canonicals, Canonical Target Not Indexable
Q30 How to specify a canonical URL with rel="canonical" and other methods 2026-10-07 Canonical Invalid, Canonical Changed
Q31 Googlebot | Google Search Central Documentation 2026-10-07 HTML Page Size
Q32 Fix Search-related JavaScript problems 2026-10-07 Content Depends on JavaScript
Q33 Fix lazy-loaded content 2026-10-07 Image Lazy Loading
Q34 Optimize your crawl budget 2026-10-07 Internal Link Through a Redirect
Q35 Link best practices for Google 2026-10-07 External Link Count, Internal Link Count, Unresolvable Link Href, Internal Link to an Error Page, Orphan Page
Q36 Robots meta tag, data-nosnippet, and X-Robots-Tag specifications 2026-10-07 Contradictory Robots Directives, Links Not Followed, Images Blocked From Indexing, Page Blocked From Indexing
Q37 Learn about sitemaps 2026-10-07 Invalid Sitemap, Orphan Page
Q38 Meta tags and HTML attributes that Google supports | Google Search Central 2026-10-07 Meta Keywords, Meta Viewport
Q39 URL Structure Best Practices for Google Search 2026-10-07 SEO Friendly URL, urlPolicy
Q40 Spam Policies for Google Web Search (Keyword stuffing) 2026-10-07 Most Used Words
Q41 Creating Helpful, Reliable, People-First Content 2026-10-07 Word Count
Q42 Search Engine Optimization (SEO) Starter Guide 2026-10-07 Multiple H1 Headings
Q43 Preventing and monitoring abuse on your site 2026-10-07 Flagged by Safe Browsing
Q44 Tell Google about localized versions of your page 2026-10-07 Hreflang Without Return Link
Q45 Tell Google about localized versions of your page 2026-10-07 Hreflang Without Self Reference
Q46 Tell Google about localized versions of your page 2026-10-07 Hreflang Code Invalid
Q100 Understanding Google Page Experience 2026-10-16 Core Web Vitals Field Data
Q104 Google's Guide to Optimizing for Generative AI Features on Google Search (Google Search does not use llms.txt; it neither helps nor harms rankings there) 2026-10-16 llms.txt File
S10 Influencing your title links in search results 2026-10-07 H1 Missing, Title Length, Title Missing, Duplicate Title, titlePattern
S11 Control your snippets in search results 2026-10-07 Meta Description Length, Meta Description Missing
S12 How to specify a canonical URL with rel="canonical" and other methods 2026-10-07 Canonical Differs From Final URL, Canonical Missing, WWW and Non-WWW Both Serve the Page, HTTP Version Not Redirected to HTTPS, Page Not Served Over HTTPS, Open Graph URL Mismatch, Internal Link Through a Redirect, Sitemap URL Not Indexable, canonicalPolicy
S13 Block Search Indexing with noindex 2026-10-07 Page Blocked From Indexing, Indexability Regression
S15 Introduction to structured data markup in Google Search 2026-10-07 Structured Data Invalid, Structured Data Missing
S16 Understand the JavaScript SEO basics 2026-10-07 Content Depends on JavaScript
S23 Google image SEO best practices (section: Use descriptive filenames, titles, and alt text) 2026-10-07 Image Alt Attribute Missing

WHATWG

IdDocumentCheckedCited by
Q08 Fetch Standard, section 3.6: X-Content-Type-Options header 2026-10-07 X-Content-Type-Options Missing
Q09 WHATWG HTML: the X-Frame-Options header 2026-10-07 Framing Protection Missing
Q48 HTML Standard, 3.2.6.2 The lang and xml:lang attributes 2026-10-07 HTML Language Attribute
Q49 HTML Standard, 4.8.4.4 Requirements for providing text to act as an alternative for images 2026-10-07 Image Alt Attribute Missing
Q50 HTML Standard, 4.6.8 Link types: noopener (and noreferrer) 2026-10-07 Unsafe External Target Blank Links
Q51 HTML Standard, 4.6.8.9 Link type "icon" 2026-10-07 Favicon
Q52 HTML Standard, 16.2 Non-conforming features 2026-10-07 Deprecated HTML Tags
Q53 HTML Standard (WHATWG), 4.12.1 The script element: async and defer attributes 2026-10-07 Render Blocking Scripts
Q54 HTML Standard: 4.3.11 Headings and outlines 2026-10-07 H1 Missing, Multiple H1 Headings, Heading Outline, Skipped Heading Level
Q55 HTML Standard, 4.2.5.4 Specifying the document's character encoding 2026-10-07 Character Encoding Declaration, headOrder
Q56 HTML Standard (4.2.5.1 Standard metadata names: description) 2026-10-07 Duplicate Meta Description, Meta Description Missing
Q57 HTML Standard, 4.2.2 The title element 2026-10-07 Duplicate Title Element, Title Missing
Q58 HTML Standard, section 7.7: The X-Frame-Options header 2026-10-07 Framing Protection Missing
Q59 HTML Standard, 13.1.1 The DOCTYPE 2026-10-07 Doctype
Q63 URL Standard (section 4.4 URL parsing) 2026-10-07 Unresolvable Link Href

web.dev

IdDocumentCheckedCited by
Q02 Time to First Byte (TTFB) | Articles | web.dev 2026-10-07 Time to First Byte
Q64 Cumulative Layout Shift (CLS) 2026-10-07 Core Web Vitals Field Data
Q65 Interaction to Next Paint (INP) 2026-10-07 Core Web Vitals Field Data
Q66 Largest Contentful Paint (LCP) 2026-10-07 Core Web Vitals Field Data
Q67 Optimize Cumulative Layout Shift (section: Images without dimensions) 2026-10-07 Image Dimensions Missing
Q68 Responsive web design basics 2026-10-07 Meta Viewport
Q69 Web Vitals 2026-10-07 Core Web Vitals Field Data
Q70 What is mixed content? 2026-10-07 Mixed Content
Q71 Why HTTPS matters 2026-10-07 Page Not Served Over HTTPS
Q94 How the Core Web Vitals metrics thresholds were defined 2026-10-16 Core Web Vitals Field Data
Q95 First Contentful Paint (FCP): good 1.8 seconds or less, poor above 3.0 seconds, at the 75th percentile 2026-10-16 Core Web Vitals Field Data
Q96 Time to First Byte (TTFB): good 0.8 seconds or less, poor above 1.8 seconds 2026-10-16 Core Web Vitals Field Data

W3C

IdDocumentCheckedCited by
Q10 W3C Content Security Policy Level 3: frame-ancestors (not supported in a meta element policy) 2026-10-07 Framing Protection Missing
Q11 Permissions Policy (W3C Working Draft) 2026-10-07 Permissions Policy Missing
Q82 Content Security Policy Level 3 (W3C Working Draft), sections 3.1 to 3.3 2026-10-07 Content Security Policy Missing
Q83 Content Security Policy Level 3, style-src-attr 2026-10-07 Inline CSS
Q84 Content Security Policy Level 3 (W3C Working Draft), section 3.3: The meta element 2026-10-07 Framing Protection Missing
Q85 JSON-LD 1.1: A JSON-based Serialization for Linked Data (section 7, Embedding JSON-LD in HTML Documents) 2026-10-07 Structured Data Invalid
Q86 JSON-LD 1.1: A JSON-based Serialization for Linked Data (section 3.5, Specifying the Type) 2026-10-07 Structured Data Type Missing
Q87 Mixed Content (W3C Candidate Recommendation Draft, 23 February 2023) 2026-10-07 Mixed Content, Form Submits Over HTTP
Q88 Referrer Policy (W3C Candidate Recommendation), sections 3, 3.8, 4.1 and 4.2 2026-10-07 Referrer Policy Missing
Q89 Understanding Success Criterion 3.1.1: Language of Page | WAI | W3C 2026-10-07 HTML Language Attribute
Q90 Understanding Success Criterion 2.2.1: Timing Adjustable | WAI | W3C 2026-10-07 Meta Refresh
Q91 Headings | Web Accessibility Initiative (WAI) | W3C 2026-10-07 Skipped Heading Level

IETF

IdDocumentCheckedCited by
Q72 RFC 3986: Uniform Resource Identifier (URI): Generic Syntax, section 2.3 Unreserved Characters 2026-10-07 SEO Friendly URL
Q73 RFC 5280: Internet X.509 Public Key Infrastructure Certificate and CRL Profile, section 4.1.2.5 Validity 2026-10-07 TLS Certificate Expiring Soon, Invalid TLS Certificate
Q74 RFC 6596: The Canonical Link Relation 2026-10-07 Conflicting Canonicals, Canonical Differs From Final URL, Canonical Invalid, Canonical Target Not Indexable
Q75 RFC 6797: HTTP Strict Transport Security (HSTS), sections 6.1.1 and 8.1 2026-10-07 HSTS Missing
Q76 RFC 7208: Sender Policy Framework (SPF) for Authorizing Use of Domains in Email, Version 1 (section 4.5, Selecting Records) 2026-10-07 SPF Record Problem
Q77 RFC 7208: Sender Policy Framework (SPF) for Authorizing Use of Domains in Email, Version 1 (sections 4.6 Record Evaluation and 5.1 "all") 2026-10-07 SPF Record Problem
Q78 RFC 9110: HTTP Semantics, section 10.2.4 Server 2026-10-07 Server Version Disclosed
Q79 RFC 9110: HTTP Semantics, section 4.3.4 https Certificate Verification 2026-10-07 Invalid TLS Certificate
Q80 RFC 9309: Robots Exclusion Protocol 2026-10-07 Blocked by robots.txt
Q81 RFC 9309: Robots Exclusion Protocol (section 2.3.1.3, Unavailable Status) 2026-10-07 robots.txt Missing

Chrome for Developers

IdDocumentCheckedCited by
Q07 Eliminate render-blocking resources | Lighthouse | Chrome for Developers 2026-10-07 Render Blocking Scripts, Render Blocking Stylesheets
Q17 Links to cross-origin destinations are unsafe 2026-10-07 Unsafe External Target Blank Links
Q18 Avoid an excessive DOM size | Lighthouse | Chrome for Developers 2026-10-07 DOM Size
Q19 Avoid multiple page redirects 2026-10-07 Redirect Chain
Q20 Keep request counts low and transfer sizes small | Lighthouse | Chrome for Developers 2026-10-07 HTTP Requests
Q21 Serve images in modern formats | Lighthouse | Chrome for Developers 2026-10-07 Images in Legacy Formats
Q22 Document request latency 2026-10-07 HTML Not Compressed
Q103 llms.txt | Lighthouse | Chrome for Developers (an emerging convention; providing the file is optional) 2026-10-18 llms.txt File
S38 CrUX API 2026-10-07 Core Web Vitals Field Data

Google for Developers

IdDocumentCheckedCited by
Q03 Overview of Google crawlers and fetchers (user agents) 2026-10-07 No Cache Validators, HTML Not Compressed, HTTP Protocol Version
Q23 How HTTP Status Codes Affect Google's Crawlers 2026-10-07 Status Code Regression
Q24 Safe Browsing Lookup API (v4) 2026-10-07 Flagged by Safe Browsing
Q47 Method: index.inspect 2026-10-07 Not Indexed in Search Console
Q92 About PageSpeed Insights (field data of the previous 28 days at the 75th percentile, origin fallback, LCP, INP and CLS thresholds) 2026-10-16 Core Web Vitals Field Data
Q93 Method: pagespeedapi.runpagespeed | PageSpeed Insights API v5 2026-10-16 Core Web Vitals Field Data
S14 How Google Interprets the robots.txt Specification 2026-10-07 Blocked by robots.txt, robots.txt Missing, Sitemap Not Declared in robots.txt

GoogleChrome/lighthouse (GitHub)

IdDocumentCheckedCited by
Q97 Lighthouse viewer, psi-api.js (PSI_DEFAULT_CATEGORIES: the categories the viewer requests from the PageSpeed Insights API, agentic-browsing included) 2026-10-16 Core Web Vitals Field Data
Q98 Lighthouse default config: the agentic-browsing category (categoryScoreDisplayMode fraction, audit references) 2026-10-16 Core Web Vitals Field Data
Q99 Lighthouse report utilities: calculateCategoryFraction() and showAsPassed() (how a fraction category counts passed audits) 2026-10-16 Core Web Vitals Field Data
Q102 Lighthouse llms-txt audit, core/audits/agentic/llms-txt.js (Markdown with an H1, links, at least 50 characters; a 4xx is not applicable, a 5xx or 429 fails) 2026-10-18 llms.txt File

OWASP

IdDocumentCheckedCited by
Q12 OWASP HTTP Headers Cheat Sheet: remove X-Powered-By, non-informative Server 2026-10-07 X-Powered-By Version Disclosed
Q15 HTTP Headers Cheat Sheet (OWASP Cheat Sheet Series), Server 2026-10-07 Server Version Disclosed
Q16 HTTP Headers Cheat Sheet (OWASP Cheat Sheet Series), X-Powered-By 2026-10-07 X-Powered-By Version Disclosed

Google Search Console Help

IdDocumentCheckedCited by
Q61 Page indexing report - Search Console Help 2026-10-07 Soft 404
Q62 URL Inspection tool - Search Console Help 2026-10-07 Not Indexed in Search Console

Let's Encrypt

IdDocumentCheckedCited by
Q14 Let's Encrypt FAQ: renew 90-day certificates every 60 days and six-day certificates every three days 2026-10-07 TLS Certificate Expiring Soon

Open Graph protocol

IdDocumentCheckedCited by
Q60 The Open Graph protocol 2026-10-07 Open Graph URL Mismatch, Open Graph Missing

llmstxt.org

IdDocumentCheckedCited by
Q101 The /llms.txt file (proposal by Jeremy Howard, v2: a Markdown file whose only required section is an H1 with the name of the project or site) 2026-10-16 llms.txt File

Rules Without an Authoritative Source

These checks rest on a project decision rather than a published requirement; their rule pages show the decision instead of a source.

Related Documentation