Research library

Google's robots.txt token for blocking AI training (Google-Extended) blocks Gemini training — but does NOT exclude a site from being used to generate AI Overviews answers. Google treats AI Overviews as a Search surface.

A Princeton study (KDD 2024) tested nine content strategies across ~10,000 queries. Adding statistics, citations, and direct quotations lifted AI citation visibility by up to ~40% — and sites that don't already rank #1 gained disproportionately more.

Academic confirmation of primacy and recency effects in LLM-generated recommendations: businesses mentioned earlier in an AI answer get noticed more. This is why Quarry records the position of every business in every AI answer, not just whether it appeared.

Yext analyzed 6.8 million citations across 1.6 million AI responses. Gemini cited brand-owned websites 52% of the time; ChatGPT cited third-party directories (Yelp, TripAdvisor, MapQuest) 49% of the time; Perplexity leaned on niche industry directories (~24%). This is why Quarry's per-engine actions differ — and why Claude has no action yet: no study in this library covers Claude's sources, and we don't guess.

Semrush's 150K-citation study found Reddit, Wikipedia, and YouTube dominate AI citations overall — and that Reddit's share of ChatGPT citations collapsed from ~60% to ~10% in about six weeks in 2025. AI visibility is volatile; that's why Quarry tracks it over time instead of treating one scan as the truth.

Similarweb measured 89% of AI referral visits coming from ChatGPT (2.8M sessions across 41 brand sites, 2025). This is why Quarry's AI Visibility Report asks ChatGPT every query in your industry's pack while the other engines get the primary question — depth where the traffic is.

Google's own documentation: local ranking comes from relevance, distance, and prominence — and "more reviews and positive ratings can help your business's local ranking." Google instructs businesses to keep info complete and accurate, keep hours up to date, respond to reviews, and add photos. Note the careful wording: photos and review responses appear under profile completeness, not ranking factors.

Google's representation guidelines: your profile name must reflect your real-world business name — adding keywords, locations, or taglines "isn't permitted, and could result in the suspension of your Business Profile." On categories: use as few as possible to describe your core business. This is why Quarry flags stuffed names as a compliance risk, not a ranking tip.

Whitespark's Local Search Ranking Factors 2026 (47 experts, 187 factors): GBP signals are the largest Local Pack factor group (~32%), 8 of the top 10 factors come directly from the profile, primary category sits at the top, and review recency/velocity rose sharply since 2023. It's an expert-opinion survey, not a measurement study — Quarry treats the trends as consensus and the exact weights as informed opinion.

BrightLocal's consumer survey (1,002 US consumers, methodology disclosed): 68% will only use a business rated 4.0+, and 31% now require 4.5+. 74% only care about reviews from the last three months. 89% expect owners to respond to reviews. And the AI crossover: AI tools jumped from 6% to 45% as a local-recommendation source in one year. These are trust-and-conversion findings — they shape what customers do, which is reason enough.

Sterling Sky's client case data (cited by Whitespark's Darren Shaw, who ranks review recency in his top 5 ranking factors for 2025): rankings dropped when new reviews stopped flowing and recovered when they resumed. Raw review count matters at a low threshold and then plateaus — but a steady, recent inflow keeps mattering. This is why Quarry weights review velocity, not just total count.

A controlled test (Sterling Sky) found adding photos had no measurable Local Pack ranking impact. A 2-million-profile analysis (Localo) found top-3 listings average 250+ photos vs ~170 for positions 11–20 — real, but correlation. Google officially recommends photos as part of a complete profile. Honest synthesis: photos matter for the people viewing your profile, not for rank — and that's why Quarry frames its photo checks as engagement, never ranking.

Google encourages replying to reviews but attributes the benefit to standing out, not ranking. 89% of consumers expect owners to respond (§7.4). High-visibility brands respond to ~80% of reviews vs a ~45% average — a correlation, not a measured lift. The widely repeated "responding boosts rankings" claim traces only to tool-vendor blogs with no methodology, so Quarry treats responding as a customer-expectation check.

Sterling Sky's category tests found that adding genuinely relevant secondary categories expands the searches a profile appears for without diluting its primary-category ranking — one documented example saw a law firm add "Employment Attorney" and improve for employment queries within ~48 hours. Google's guideline says use as few categories as possible, so the rule is relevance: helpful when the category truly fits, a guideline risk when you stack marginal ones. That's why Quarry's check requires relevant categories.

A controlled test (Sterling Sky) — one post a week for nine weeks across three listings, 441 tracked keywords each — found posting had no measurable impact on Local Pack rankings. Posts still help engagement and keep a profile looking active. Quarry keeps its recent-post check as a freshness/engagement signal and its copy never implies a ranking effect.

Sterling Sky tested keyword-rich Q&A across multiple listings: no ranking impact. Separately, Google discontinued the Business Profile Q&A API in November 2025 with no replacement — the feature is being wound down in the AI-answers era. Quarry removed Q&A from scoring accordingly.

Since late 2023, whether a business is currently open materially affects Local Pack rank — documented listings dropped from #1 to #10+ when closed and recovered when open, replicated across industries. Google corroborates in writing: temporarily-closed businesses can rank after open ones. Accurate hours are the precondition for this signal working in your favor — that's why the hours check matters more than it looks.

SOCi analyzed 350,000+ locations across 2,751 multi-location brands: AI platforms recommend only 1.2% of locations on ChatGPT, 7.4% on Perplexity, 11% on Gemini — versus 35.9% getting Google 3-pack visibility. Only ~45% overlap between brands winning traditional local search and brands recommended by AI. Recommended locations average ~4+ stars: ratings act as an inclusion filter. This gap is why AI visibility is its own pillar in Quarry, not a footnote to the Map Pack. (SOCi competes in this category — framed accordingly.)

Sterling Sky's single-variable testing (Feb 2026) found that populating the structured GBP "Services" field produces a measurable Local Pack ranking lift, with documented before/after examples across multiple industries — the effect typically appears within 24–72 hours. Sterling Sky calls it a powerful, under-utilized lever. This grounds Quarry's Services check, which replaced an older description-keywords check that had no ranking evidence.

Google's title-link documentation instructs that every page carry a descriptive <title>, and lists the title element first among the sources it uses to generate the clickable title in results (og:title and the first visible H1 are also listed). Google frames titles as critical for users; it doesn't quantify a ranking weight. Quarry's title and H1 checks rest on this.

Google may use the meta description for a result's snippet when it describes the page better than other on-page text — a snippet and click-through quality input, not a ranking signal. Quarry keeps its meta-description check, framed honestly as a click-through (not ranking) lever.

Google's official site-experience triad: Largest Contentful Paint ≤ 2.5s, Interaction to Next Paint < 200ms, Cumulative Layout Shift < 0.1 — assessed at the 75th percentile of real-user field data. INP replaced FID as the responsiveness metric in March 2024. Quarry's LCP, CLS, and INP checks grade against these official bands.

Google's page-experience documentation: "Core Web Vitals are used by our ranking systems" — and in the same breath, chasing perfect scores "may not be the best use of your time," because relevance wins even when page experience is sub-par. Real signal, modest weight — which is exactly how Quarry weights its speed checks.

Schema.org's authoritative LocalBusiness vocabulary defines the subtype tree Quarry maps each vertical to (Dentist, Restaurant, InsuranceAgency, ExerciseGym, and so on) plus standard properties — name, address, telephone, url, geo, opening hours, sameAs. It's the basis for Quarry's per-vertical schema-type matching.

Google's official local-business structured-data documentation: only name and address are required, more properties mean higher quality, and — quoted directly — "Use the most specific LocalBusiness sub-type possible." This is why Quarry flags schema that uses a generic type when a specific one exists for your industry.

Google's structured-data policies state plainly that a structured-data manual action means a page "loses eligibility for appearance as a rich result; it doesn't affect how the page ranks." Schema's honest value is rich-result eligibility, disambiguation, and machine readability (increasingly relevant for AI surfaces) — never a ranking lift. Quarry's schema checks are worded to match.

Google confirmed HTTPS as a ranking signal in 2014 — "a very lightweight signal… carrying less weight than other signals such as high-quality content" — and it remains a page-experience criterion today. Quarry's HTTPS and redirect checks rest on this and Google's canonical-selection guidance.

Google's transition to mobile-first indexing is complete: all sites are crawled primarily with the mobile Googlebot, and the dedicated mobile-friendly ranking boost and test tool were retired, with mobile usability folded into page experience. Quarry's mobile-viewport check is a proxy for "displays well on mobile," an official page-experience criterion.

Google's John Mueller, repeatedly and explicitly: the number of words on a page is not a quality factor or ranking factor. The famous "300 words" figure is an old plugin convention. Quarry keeps a thin-content check only as an honestly-labeled heuristic — a 50-word service page rarely answers anyone's question — never as a ranking claim.

Google made page speed a mobile ranking factor in 2018 (affecting only the slowest pages, since folded into page experience). But the Lighthouse 0–100 score itself is NOT what Google ranks on — rankings use real-user field data, and Google endorses no passing score. Quarry's mobile-50/desktop-70 bars are internal heuristics mapped to Lighthouse's display bands, and the check copy says so.

Google uses alt text together with computer-vision algorithms and page content to understand what an image shows — it's the single most important image attribute for Search and accessibility, and keyword-stuffed alt text can be treated as spam. There's no official coverage threshold (Quarry's 90% bar is internal calibration, and its copy says so).

Whitespark's 2026 survey rates on-page signals the most important factor group for local organic results — with "a dedicated page for each service" the #1 factor and localized content / city-keyword placement rated highly. Important honesty point: no Google document says "put your city in your title or H1" — these are expert-consensus signals plus the general mechanism that descriptive titles aid relevance. Quarry labels them as consensus, not "Google says so."

Google's documentation: rel=canonical is "a hint, not a rule" — Google selects canonicals using HTTPS, redirects, sitemap inclusion, and internal linking, with near-duplicate location pages the textbook case. Small, well-linked sites (~500 pages or fewer) may not need a sitemap, and malformed hreflang tags are silently ignored. This grounds Quarry's canonical, redirect, sitemap, and hreflang checks.

A page carrying a noindex directive is removed from Google Search results — definitional, and the strongest-evidenced check in Quarry's entire suite. If a page that should rank is accidentally noindexed, nothing else about it matters until that's fixed.

The Open Graph protocol (og:title, og:type, og:image, og:url required; og:description recommended) is a social-preview standard — not a Google ranking signal. Its two honest values: clean link previews in social and messaging apps, and machine-readable page metadata that Google's title-link docs list as a title source. Quarry weights its Open Graph checks modestly to match.

Google restricted FAQ rich results to government/health sites in 2023 and fully deprecated them for all sites by 2026 — FAQPage schema now produces no Google SERP feature. But FAQ-format CONTENT remains valuable: Microsoft officially recommends Q&A formats for inclusion in Copilot answers, and a business's own site is the dominant source ChatGPT cites for local questions. So Quarry's FAQ check is a content check, never a (dead) schema recommendation.

Google's March 2024 core update folded the Helpful Content System into core ranking and launched spam policies targeting scaled content abuse. For multi-location brands this matters directly: templated, near-identical city or location pages are exactly the pattern these policies target — location pages need genuinely differentiated local content. This is why Quarry's local-content checks reward substance over boilerplate.

Google's official AI-optimization guide (May 2026) says appearing in its AI features takes no special files, no llms.txt, no AI-specific markup — "structured data isn't required for generative AI search." Solid SEO fundamentals and Business Profile data are what feed Google's AI answers. Note the engine split: Google downplays schema for its AI surfaces while Microsoft recommends it for Copilot (§9.3) — Quarry's recommendations name engines for exactly this reason.

Microsoft's official guidance for inclusion in Copilot / Bing AI answers recommends JSON-LD schema markup, clear heading structure, Q&A formats, lists and tables, and self-contained sentences — and warns against content hidden in tabs, PDFs, or images. Copilot is powered by Bing's index, so traditional Bing SEO and Bing Places listings drive AI-answer visibility on Microsoft surfaces.

Each engine now documents which crawler controls SEARCH visibility separately from training: OpenAI says blocking OAI-SearchBot means your site "will not be shown in ChatGPT search answers"; Anthropic's Claude-SearchBot and Perplexity's PerplexityBot control the same for their engines. A robots.txt that blocks these makes a business structurally invisible to AI search regardless of everything else.

A large-scale academic comparison of AI search engines vs Google found a "systematic and overwhelming bias towards earned media" — third-party, authoritative sources — over brand-owned and social content, plus significant engine-to-engine divergence. Independent academic convergence with the per-engine citation studies (§3.1): being written about beats writing about yourself, for AI visibility.

Ahrefs tracked 1.9M US queries: Grok's top cited domains are Reddit (16.3%), YouTube (15.1%), and Facebook (13.9%) — heavily social/UGC. Surprisingly, X itself is only ~1.4% of citations. Grok isn't a Quarry scan engine yet; if it's added, social presence carries unusual weight there.

BrightLocal manually analyzed 800 local-intent ChatGPT queries: business websites made up 58% of cited local sources, brand mentions in articles and lists 27%, directories 15% — and within directories, Yelp was absent. That openly disagrees with the broader-query Yext data (§3.1), where ChatGPT leaned on Yelp-style directories heavily. Both stay cited; the honest takeaway is that your own site's content carries the most weight for local AI answers, and directory presence is corroboration, not a promised citation.