Reference
AI search visibility, documented.
21 AI visibility platforms scored on the same five dimensions. 19 engine profiles covering how each one retrieves, grounds, and cites. 44 defined terms. The funding map behind the category. Every figure sourced and dated.
Two disciplines sit underneath all of it. Answer Engine Optimization (AEO) covers the extractive surfaces: featured snippets, voice, AI Overviews. Generative Engine Optimization (GEO) covers the grounded generative engines: ChatGPT Search, Perplexity, Claude, Gemini, Bing Copilot. They share a foundation; the success metrics differ.
Guides
All guides →Long-form editorial on the disciplines, implementation, and measurement.
Foundations · AEO + GEO · 12 min
AEO vs GEO: how Answer Engine Optimization and Generative Engine Optimization actually differ
Two disciplines, one shared foundation, meaningfully different KPIs, and why most practitioners blur them incorrectly
Implementation · GEO · 11 min
The llms.txt specification, in depth
What llms.txt actually is, what llms-full.txt adds, who's adopting it, and how to ship one that AI engines might actually use
Implementation · AEO + GEO · 13 min
Schema.org for AEO and GEO: which structured data actually matters
Schema.org has hundreds of types. Only a small subset moves the needle for AI engines, and the priority order is not obvious
Foundations · AEO + GEO · 11 min
Citation-worthy content patterns: writing for both extraction and grounding
The editorial patterns that survive both AEO extraction and GEO grounding, and the patterns that lose in both
Vendor matrix
All vendors →21 AI visibility and citation-tracking platforms scored on the same five dimensions. Includes GrackerAI with explicit author-conflict disclosure.
Who funds GEO
Investor landscape →The capital map of AI search visibility: the first unicorn round, the VCs placing repeat bets, Adobe's $1.9B acquisition of Semrush, and the bootstrapped indies. Sourced and dated.
Decision tools
All tools →Free interactive tools: llms.txt generator, schema validator, AI Visibility Scorecard, Citation Tracker Quickstart. No email gate; everything runs in your browser.
AI engine profiles
All engines →How each AI search engine grounds, what it cites, and what it rewards, covering both the extractive AEO surfaces and the grounded GEO engines.
OpenAI
ChatGPT Search
OpenAI's web-grounded mode inside ChatGPT, surfaced as 'Search' and rolled into the default model behavior for queries the model judges to benefit from fresh information. Grounded answers cite a panel of web sources alongside the assembled response.
Perplexity AI
Perplexity
Perplexity is a search-first AI engine: every answer is grounded against retrieved sources by default, with a heavily citation-forward UI. Has been the most aggressive engine in the citation-frequency race and the most read by SEO teams as a leading indicator of GEO signal.
Anthropic
Claude
Anthropic's Claude is a conversational AI with optional web search grounding (introduced in 2025). Claude leans more cautious about citation than ChatGPT or Perplexity. It grounds when the model judges fresh information is necessary and surfaces sources in a side panel rather than inline. The grounding behavior is more conservative, the citations more curated, and the answer style more long-form.
Google
Gemini
Google's Gemini app (and the embedded Gemini features across Google's product surface) is grounded against Google's search index when the conversation calls for current information. Distinct from Google AI Overviews: Gemini is the conversational interface, AI Overviews is the SERP-integrated answer block. Both consume Google's grounding infrastructure but surface citations differently.
Google
Google AI Overviews
AI Overviews is the SERP-integrated answer block Google began rolling out in 2024 (formerly 'Search Generative Experience' or SGE). It appears at the top of search results for queries Google judges to benefit from an assembled answer, citing 3-10 sources. AI Overviews is the most consequential AEO surface for sites that already rank well in traditional Google search.
Microsoft
Bing Copilot
Microsoft Copilot (formerly Bing Chat, now extending across Bing, Edge, and Windows) is grounded against Bing's search index and shares OpenAI's GPT-4-class models. Less consumer reach than Google AI Overviews but increasingly important as Microsoft pushes Copilot through Edge, Windows, and Microsoft 365 surfaces, and as enterprise buyers consolidate on Microsoft AI tooling.
Google
Google AI Mode
Google AI Mode is the conversational AI surface inside Google Search, distinct from AI Overviews. Where AI Overviews is a passive answer block embedded above the organic results, AI Mode is an active chat experience: the user opts in, asks multi-turn questions, and gets a Gemini-powered conversational answer with inline citations. Rolled out broadly in 2025 after the SGE / AI Overviews launch. Heavy use of query fan-out (one user question expanded into multiple sub-queries) means retrieval reaches further down Google's index than classical SERP rankings would suggest.
xAI
Grok
Grok is xAI's chatbot, originally exclusive to X (Twitter) Premium subscribers and broadly accessible at grok.com from 2025. Grok 3 introduced DeepSearch in early 2025, a multi-step research mode that crawls the web and assembles long-form cited answers. Distinctive feature: heavy weighting of real-time X (Twitter) posts as a grounding source, which gives Grok citation behaviour unlike any other major engine. Strong on breaking news, weak on long-tail editorial content where X conversation is sparse.
Meta
Meta AI
Meta AI is Meta's assistant powered by Llama models, embedded in Facebook, Instagram, WhatsApp, Messenger, and the standalone meta.ai web app. Search grounding is provided via a Bing-derived web index (Meta's longstanding partnership with Microsoft). The discovery surface inside Meta's apps (1.5+ billion monthly users for the assistant across surfaces by mid-2026) makes it consequential for consumer queries even though the dedicated web experience is less prominent than ChatGPT or Perplexity.
DeepSeek (China)
DeepSeek
DeepSeek is a Chinese AI lab whose chat interface at chat.deepseek.com gained global prominence in early 2025 when DeepSeek-R1 (a reasoning model) launched at a fraction of the cost of comparable Western models. DeepSeek Chat offers free access to both V3 (general-purpose) and R1 (reasoning) modes with web search grounding. Strong in Chinese-language queries; growing English-language usage as a free alternative to ChatGPT and Claude.
Mistral AI (France)
Mistral Le Chat
Le Chat is Mistral AI's conversational interface, headquartered in Paris and operated under EU jurisdiction with GDPR alignment as a stated differentiator. Web search grounding was added in 2024 and substantially expanded in 2025 with the 'Mistral Le Chat Pro' tier. Particularly strong adoption in European enterprise and EU-public-sector contexts where data residency and GDPR compliance matter. Powers Mistral's enterprise APIs as well.
Alibaba Cloud (China)
Qwen Chat (Tongyi Qianwen)
Qwen Chat is Alibaba Cloud's conversational AI, powered by the Qwen model family (Qwen2.5, Qwen3, and successors). Strong in the Chinese market and across Asia, with web search grounding integrated into the chat experience. Open-source Qwen variants are widely deployed across the Chinese AI ecosystem, giving Alibaba meaningful upstream influence on what content is well-represented in Chinese-language AI surfaces.
Baidu (China)
Baidu AI Search
Baidu is the dominant search engine in mainland China, and Baidu Search now surfaces AI-generated answers at the top of the SERP for many query types (analogous to Google AI Overviews). Baidu also operates ERNIE Bot (文心一言, Wenxin Yiyan) as a standalone conversational AI. For any publisher targeting Chinese-language audiences, Baidu's AI surfaces are the single most consequential AI search channel: Google has effectively no presence in mainland China.
Moonshot AI (China)
Moonshot Kimi
Kimi is Moonshot AI's chat product, distinguished early by very long context windows (initially 2M tokens, expanded subsequently) which made it the preferred Chinese AI for document analysis and long-form research. Strong adoption in Chinese knowledge-work and academic contexts. Web search grounding is integrated; the long-context capability lets Kimi consume entire retrieved documents rather than chunked snippets.
Yandex (Russia)
Yandex Neuro
Yandex Neuro is the AI-generated answer surface inside Yandex Search, the dominant search engine in Russia and several CIS countries. Yandex also operates YandexGPT as a standalone chatbot. For Russian-language publishers and Western publishers with Russian-language content targeting CIS markets, Yandex's AI surfaces are the meaningful AI search channel (Google has reduced presence in Russia post-2022).
Naver (South Korea)
Naver AI Search (HyperCLOVA X)
Naver dominates South Korean search (60 to 70% domestic market share, well above Google). Naver Search integrates HyperCLOVA X-powered AI answers for relevant queries, and Naver also operates standalone AI products on top of HyperCLOVA X. For any publisher targeting Korean-language audiences, Naver's AI surfaces are the primary AI search channel.
You.com (US)
You.com
You.com is a multi-mode AI search product offering Smart, Genius, and Research modes with different depths of retrieval and reasoning. Less consumer traction than Perplexity or ChatGPT Search in 2026, but maintains a citation-heavy interface and a developer-friendly API. Notable as one of the earlier AI search products (launched 2022) that continues to operate independently.
Phind (US)
Phind
Phind is a developer-focused AI search engine, oriented toward technical queries, code snippets, and documentation. Particularly strong on programming, cybersecurity, DevOps, and infrastructure topics. For any publisher in technical verticals (developer tooling, cybersecurity, identity, infrastructure), Phind's citation share is disproportionately consequential relative to its consumer-search share.
Brave (US)
Brave Leo
Leo is the AI assistant integrated into the Brave browser, with privacy-first defaults: queries do not require accounts, are not retained, and are not tied to user identifiers. Backed by Llama and Mistral models with optional premium access to Claude. Less consequential for raw citation share than the major engines, but meaningful for publishers reaching privacy-conscious or developer audiences who use Brave as a daily browser.
Glossary
All terms →The vocabulary of AI search, defined, dated, and citable.
GEO (Generative Engine Optimization)
The discipline of getting your content picked up, grounded against, and cited by generative AI search engines like ChatGPT Search, Perplexity, Claude, Gemini, and Google AI Overviews.
AEO (Answer Engine Optimization)
The discipline of structuring content so answer engines (Google AI Overviews, featured snippets, People Also Ask, voice assistants) extract your page as the direct answer. The older sibling of GEO; the two converge but are not synonyms.
RAG (Retrieval-Augmented Generation)
The architecture pattern where an AI engine retrieves source documents from a corpus before generating an answer, conditioning the response on the retrieved context. The technical foundation underneath both AEO and GEO.
AIO (AI Overviews / AI Optimization)
Two distinct meanings sharing the same acronym. Most often refers to Google's AI Overviews: the SERP-integrated AI answer block. Sometimes used as a catch-all for AI Optimization across all engines (a near-synonym for GEO + AEO).
llms-full.txt
A companion to llms.txt that contains the full Markdown content of a site's priority pages concatenated into a single file, intended for AI engines that prefer single-fetch corpus ingestion.
Citation share
The GEO equivalent of organic share of voice: the percentage of AI engine answers in a query set that cite your domain. The primary KPI for measuring AI visibility programs.
Grounding model
The specific architecture an AI engine uses to retrieve and condition its answer on external sources. Differs meaningfully across engines and is the variable that determines which content gets cited.
Schema.org for AEO and GEO
The subset of Schema.org structured data types that AI engines (both extractive AEO and generative GEO) prioritize for grounding signals. Not every schema type carries equal weight.
Methodology, in public
How GEO Compass evaluates engines, scores AI visibility, and what counts as a citation. No hidden scoring; the whole framework is one page.