Soft 404
A soft 404 is a URL that returns an HTTP 200 OK status to crawlers but serves content indistinguishable from a real "page not found" error — an empty result, a thin error message, or a generic fallback. Google flags soft 404s in Search Console because they waste crawl budget and pollute the index with effectively missing pages. Why it matters: Single-page apps and React or Vite sites are especially prone to soft 404s, because client-side routing can render a 404 UI while the server quietly returns 200. The fix is to emit a proper 404 status (or a prerender-status-code 404 meta tag for prerendered SPAs) so search engines and AI crawlers cleanly drop the URL instead of indexing a ghost. Auto-redirecting frequently-hit 404s to the best-match live page is a complementary defense.
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Google AI Mode is Google's dedicated conversational search experience that replaces the traditional ten-blue-links interface with a multi-turn, AI-generated answer surface powered by Gemini. Unlike AI Overviews — which appear above standard SERPs — AI Mode is a separate destination where users ask follow-up questions, refine queries, and receive synthesized responses with inline citations. Why it matters: AI Mode represents Google's commitment to AI-first search and is rapidly becoming the surface where high-intent commercial and research queries are answered. To be cited in AI Mode, brands need strong entity signals (Wikidata, Knowledge Graph), structured data, authoritative third-party mentions, and content written to answer questions in clear, extractable passages. Optimizing for AI Mode is core AEO and GEO practice.
SearchGPTSearchGPT is OpenAI's AI-powered search product (now integrated into ChatGPT Search) that retrieves real-time web information and synthesizes it into conversational answers with inline source citations. It uses a combination of OpenAI's own crawler (OAI-SearchBot), Bing's index, and live web fetching to ground responses in current information rather than relying solely on the model's training data. Why it matters: SearchGPT is the dominant AI search surface for ChatGPT's hundreds of millions of users. Brands that earn citations here capture traffic and trust that previously went to Google. Optimization requires the same fundamentals as AEO: structured data, strong topical authority, third-party mentions, and content written in clear, citation-friendly passages.
ClaudeClaude is Anthropic's family of large language models, used in the Claude.ai consumer app, the Claude API, and embedded in major enterprise tools (Notion AI, Slack AI, Zoom, Quora's Poe). Claude is known for long-context reasoning, careful citation behavior, and lower hallucination rates on factual queries. Its web-browsing variants use the ClaudeBot crawler to fetch fresh information. Why it matters: Claude has become a primary research surface for executives, journalists, and analysts — exactly the audiences most valuable to a PR-driven brand. Earning Claude citations requires the same AEO fundamentals (schema, entity signals, third-party authority) plus an allowed ClaudeBot in robots.txt and a clean llms.txt file.
GrokGrok is xAI's large language model, integrated natively into X (formerly Twitter) and available standalone. Grok has unique real-time access to the X firehose, which makes it the dominant AI engine for breaking news, social sentiment, and live event queries. It also indexes the open web for grounded answers. Why it matters: For brands whose audiences live on X — crypto, AI, startup, finance, and political verticals — Grok visibility translates directly to in-platform discovery. Optimization combines standard AEO (schema, entity signals) with an active, on-brand X presence that produces the social signals Grok weights heavily.
Bing CopilotBing Copilot (formerly Bing Chat) is Microsoft's conversational AI search experience, powered by a combination of OpenAI GPT models and Microsoft's own retrieval stack. It surfaces in Bing.com, Microsoft Edge, Windows, and Microsoft 365, and shares its index with ChatGPT Search. Why it matters: Although Bing's market share is smaller than Google's, Copilot citations carry outsized weight: they appear inside enterprise workflows (Outlook, Word, Teams) where buying decisions happen. Optimization requires IndexNow submission, strong schema markup, and content that ranks for the underlying Bing query — because Copilot still draws heavily from the top organic results.
Passage IndexingPassage indexing is the search-engine practice of indexing and ranking individual passages within a long page — rather than treating the whole page as a single unit. Google launched passage indexing in 2021, and AI search engines have adopted an even more aggressive version: when a model answers a question, it cites the specific passage that contained the answer, often from deep within a long article. Why it matters: A 4,000-word pillar guide can be cited dozens of times from dozens of different passages. The implication for AEO is that internal structure matters as much as overall topic relevance — clear H2/H3 hierarchy, self-contained passages, and answer-shaped paragraphs all increase citation surface area.