Search engines use artificial intelligence (AI) to interpret what you mean, find relevant pages, rank them, and—when a generative feature is active—summarize information from those pages in a conversational answer. AI does not replace the web index or ordinary search results: it works with crawling, indexing, ranking, and other systems that determine which sources are worth showing.
How AI fits into a search engine
A search engine does more than match the exact words in a query to words on a page. It has to infer intent, find useful candidates across an indexed web, weigh different signals, and present results. AI contributes at several points in that process. Generative AI adds another layer: using retrieved material to compose an answer.
- Interpret the query. Language models and other systems help infer meaning, including spelling variations, synonyms, language, location, and the kind of information being sought. Google says its ranking signals and their relative importance can vary by query type. Google’s explanation of how results are ranked describes these broad factors.
- Retrieve candidate pages. Search engines crawl pages and organize them in indexes. AI can help connect a query to a page that expresses the same idea using different words. Google describes neural matching as relating representations of concepts in queries and pages; Microsoft says Bing crawls and indexes the web before ranking results. Google’s ranking-systems guide and Microsoft’s explanation of Bing search outline these processes.
- Rank and assess results. Systems combine signals to estimate relevance and usefulness. Google names RankBrain, neural matching, and passage ranking among its AI systems, while its ranking explanation groups factors such as relevance, quality, usability, and context. Microsoft describes machine-learned ranking, automated signals, and human- or AI-assisted labels.
- Generate an answer when a generative feature is used. The engine can draw on retrieved pages and compose a response, sometimes with links or source references. Google describes this as retrieval-augmented generation: Search retrieves up-to-date pages, then uses information from them to generate an answer. Its systems may also use “query fan-out”—running related searches to collect information from multiple angles. Microsoft says Copilot Search uses Bing results for the original query and additional searches issued for the user. See Google’s guide to generative AI features in Search and Microsoft’s Copilot Search description.
What AI systems do in Google Search
Google describes several distinct systems rather than one universal AI switch. Their roles are not interchangeable, and the presence of a system in Search does not mean every query uses it in the same way.
RankBrain and neural matching
Google says it launched RankBrain in 2015 to help relate words to concepts, so Search can return relevant material even when a page does not use the exact words in a query. Neural matching also connects concepts represented in queries and pages. These capabilities help with meaning-based matching, not just literal keyword overlap. Google’s 2022 overview of AI in Search introduced RankBrain and related examples; its current systems guide describes neural matching.
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Passage ranking
Passage ranking helps Google identify relevant sections within a page. That can make a page useful for a query even if the whole page is not focused narrowly on that exact question. It is a way of assessing portions of a document; it does not mean every passage is indexed or displayed as a separate webpage.
MUM
Google says its Multitask Unified Model (MUM) can understand and generate language, but is not used for general Search ranking. Google has described specific applications for it. For example, its 2022 overview cited improvements to searches related to COVID-19 vaccines at that time; that historical example should not be read as a complete list of MUM’s current uses.
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How generative search answers relate to regular results
AI Overviews in Google Search and Copilot Search in Bing add generated responses to search experiences. They do not make crawling, indexing, or ranking irrelevant. Google’s guidance says its generative Search features rely on core Search systems and retrieved web information. Microsoft says Copilot Search is grounded in Bing results and additional searches. Both companies describe a combination of search infrastructure and answer synthesis, not a standalone chatbot that bypasses the web.
The experience can vary: a generated answer may appear alongside a conventional result list, and not every query or user will necessarily see the same feature. Microsoft says Copilot Search availability can depend on device, market, and browser. Google’s current Help page explains how AI Overviews appear and work; Google’s 2024 announcement of expanded generative Search features is a dated description, not a guarantee of current availability in every location. Google’s May 2024 announcement provides that historical context.
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Why AI search answers still need checking
A generated response is a synthesis, not proof that every statement is correct, complete, or supported by the linked page. Google explicitly cautions that “AI Overviews can and will make mistakes.” Microsoft likewise advises users to verify generative responses against source websites. Links and citations are useful because they give you a route to the underlying material, but they do not remove the need to inspect it—especially for medical, financial, legal, safety, or disputed claims.
- Open the cited source and check whether it actually supports the answer.
- Compare important claims with more than one credible source.
- Look for missing context, dates, exceptions, or disagreement that a short generated summary may omit.
Google’s warning and guidance appear on its AI Overviews Help page; Microsoft’s advice is included in its Bing search-results guidance.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What published performance claims do—and do not—show
Companies sometimes report results from changes to their own search systems. For example, Google said that after its March 2024 changes finished rolling out on April 19, Search had 45% less low-quality, unoriginal content than the baseline used for that work. This is Google’s reported outcome, not an independently audited measure or a measure of generated-answer accuracy. Google’s update announcement describes the claim and its context.
In August 2025, Google VP and Head of Search Liz Reid wrote that Google continued to send billions of clicks to the web each day and was committed to prioritizing the web in its AI Search experiences. That is Google’s own account of its traffic and priorities, not independent verification. Reid’s statement discusses the company’s position. Neither these claims nor the product descriptions establish that one search engine is more accurate overall; the cited official materials do not provide a controlled independent comparison.
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