What Is AI Search?

AI search is the umbrella term for search experiences in which a large language model interprets the query, gathers information, and generates the response. It spans three product shapes: standalone AI assistants with web access (ChatGPT, Perplexity, Claude, Grok), generative layers on classic search engines (Google AI Overviews and AI Mode, Microsoft Copilot), and long-running agentic modes (Deep Research) that autonomously browse dozens of sources before answering.

What retrieval architectures sit underneath?

Under every AI search product is a variant of retrieval-augmented generation, but the plumbing differs in ways that matter for visibility:

• Own-index engines — Google (AI Overviews draw on Google's index) and Perplexity (its own crawl and index via PerplexityBot).
• Partner-index engines — ChatGPT Search and Copilot lean on Bing's index, which quietly makes Bing Webmaster Tools a ChatGPT visibility lever.
• Grounding APIs — Gemini exposes Google Search grounding; models fetch live results at answer time.
• On-demand fetchers — user-triggered agents (ChatGPT-User, Claude's fetcher, MistralAI-User) that read specific pages during a conversation.

A brand can be visible in one architecture and absent from another, which is why per-engine visibility measurement is the norm.

What is the market landscape in 2026?

Scale arrived fast. ChatGPT passed 800 million weekly active users in 2025, two and a half years after launching in November 2022. Google rolled AI Overviews out from May 2024 to over a billion users and added the fully conversational AI Mode. Perplexity built the citation-first researcher niche; Copilot ships inside Windows and Microsoft 365; regional players and open-weight-based assistants fragment the long tail. For brands the operative fact is distribution: buyer questions that once produced a SERP now produce a synthesized shortlist, engine by engine.

How does AI search change optimization?

The query is conversational, the result is a composed answer, and the winner's circle holds three to five names. Optimization accordingly shifts from ranking pages to earning mentions and citations — the discipline of GEO — with tactics spanning extractable content, entity consistency, crawler access, and third-party consensus across every corpus these systems retrieve from.

Example

The same query — "top e-signature tools" — yields a link list on classic Google, a five-vendor synthesized shortlist in AI Mode, a cited comparison in Perplexity, and a two-vendor recommendation in a ChatGPT conversation. Four AI search surfaces, four different visibility outcomes to measure.