There is no single AI search engine to optimize for. The market splits across a handful of large surfaces and a long tail of specialists, and they rarely agree on which sources to cite. This directory maps the field. It is a cluster page under the AI search visibility pillar; for how these engines work, see what is AI search.
The major players
Google AI Overviews and AI Mode
The largest surface by reach. AI Overviews appear on roughly 18-20% of searches with no opt-in; AI Mode is a conversational experience that passed 1 billion monthly users in 2026. Both fan queries into sub-queries and merge the results. If you optimize for one engine, start here.
ChatGPT Search
Web search inside ChatGPT, on every plan including free. Combines model reasoning with fresh web results and post-generation citations. An estimated 250-500 million queries per week. Leans on training data for settled facts, live search for fresh ones.
Perplexity
The answer engine built around sourcing. Real-time search on every query, numbered inline citations, strong free tier. Crossed 1 billion monthly queries in Q1 2026. Often ranked first for general research use.
Microsoft Copilot
Grounded in Bing, embedded across Windows, Edge, and Microsoft 365. Uses sequential grounding, querying Bing in steps. Best reach inside the Microsoft ecosystem and enterprise desktops.
Comparison at a glance
| Engine | Backing / source pool | Citations | Free tier | Best for |
|---|---|---|---|---|
| Google AI Overviews | Google index | In-summary links | Yes | Broadest reach |
| Google AI Mode | Google index (fan-out) | Inline | Yes | Conversational research |
| ChatGPT Search | Training data + live web | After answer | Yes | General assistant use |
| Perplexity | Multiple search APIs, live | Inline numbered | Yes | Sourced research |
| Copilot | Bing | Attributed | Yes | Microsoft ecosystem |
| Grok | X plus web | Inline | Paid/limited | Real-time, social |
| You.com | RAG, live web | Inline | Yes | Customizable search |
| Brave Search | Independent index | AI answers | Yes | Privacy |
Notable specialists
Grok — Best for real-time and social signals, with direct access to X for breaking news and trends.
You.com — RAG-based with inline citations and customizable modes; strong for controllable, source-backed answers.
Brave Search — Independent index with built-in AI answers and no tracking; a solid privacy-first option.
DeepSeek — Competitive open-source alternative that has gained ground on cost and capability.
Kagi — Paid, ad-free search with AI features for users who want a clean, unbiased result set.
Komo — Fast, chat-style AI search focused on simplicity and speed.
Andi — Lightweight, card-style answers built for quick everyday questions.
Why you can't pick just one
These engines pull from different source pools and rank with different mechanisms. Only about 12% of cited sources match across platforms for the same query. A page cited by Perplexity may be invisible in AI Overviews. Prioritize by where your audience actually searches, then broaden coverage. Google's surfaces plus ChatGPT and Perplexity cover most B2B and consumer research in 2026.
How to prioritize
Google AI Overviews and AI Mode — unavoidable reach.
ChatGPT Search — huge query volume, free access.
Perplexity — high-intent researchers, transparent sourcing.
Copilot — if your buyers live in Microsoft tooling.
The specialists — only where your niche audience concentrates.
See where you stand
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