How Copilot Chooses Its Sources via the Bing Index

Microsoft Copilot chooses its sources via the Bing index. When Copilot answers a question with information from the web, it composes a search query, pulls results from Bing and builds an answer from them with numbered citations. So if you want to be cited in Copilot, your visibility in Bing is the deciding factor, not your visibility in Google. In this article you will read how that source selection works, why it is a blind spot for anyone who only focuses on Google, and what you can do about it. This is part of generative engine optimization.

How does Copilot choose its sources?

Copilot selects sources by sending a search query to Bing for a given question and using the returned pages as the basis for its answer. The model therefore does not draw only on its training memory, but pulls fresh information from Bing’s web index. That retrieving and substantiating is called grounding: the AI anchors what it says in real, retrievable pages. To understand how this process works in general, read grounding: how AI determines what is true.

In broad strokes, it goes like this:

• Copilot translates your question into a search query. It does not send your full prompt to Bing, but a short query of a few words derived from your question.
• Bing delivers results from its index. Only pages that Bing knows and has indexed are eligible. What Bing does not have does not exist for Copilot at that moment.
• The model reads a set of pages and composes an answer. It usually combines several sources, not just one.
• Copilot shows numbered citations. Below or beside the answer are clickable references to the pages used, since late 2025 also with the publisher’s name attached.

The key point for you: the first link in that chain is the Bing index. If you are not in it, or poorly represented, you simply do not make it into the set of sources Copilot is allowed to choose from. You see this same “retrieve, read, cite” logic with other assistants too. How that plays out at OpenAI we describe in getting found in ChatGPT.

Why does Copilot lean on the Bing index?

Copilot leans on Bing because Microsoft owns both, and Bing’s web index has for years been the engine behind its search products. When Microsoft built generative AI into its search and assistant layer, the logical source of current web data was its own index, not a competitor’s. Microsoft couples that index to the reasoning power of a language model, so that answers are substantiated with retrieved data rather than with potentially outdated knowledge from training.

In practice this means Copilot rides on everything Bing already knows about the web: which pages exist, how often they are updated and how trustworthy they appear. For brands, the playing field shifts as a result. The question is no longer only “do I rank in Google”, but also “does Bing know and trust my pages enough to serve them to Copilot”. That is a different channel, with its own crawler, its own index and its own signals.

Why is this a blind spot for Google marketers?

The blind spot lies here: many B2B marketers have for years optimised exclusively for Google and assume that strong Google performance automatically carries over to AI assistants. That is not true for Copilot. Copilot looks at Bing, and Bing is a separate index with its own crawler. A page that is neatly indexed in Google may be missing from Bing, crawled slowly there or ranking weakly. In that case you are visible in Google and undiscoverable in Copilot, without realising it.

That gap opens up quietly. Bing and Google share many principles, but differ in how they crawl, how quickly they pick up new pages and which sites they already have well in view. Anyone who has never opened a Bing account simply has no insight into whether their most important pages are even there. And it is precisely those pages, your product explanations, your comparisons, your answers to buying questions, that are the content you want to surface in a Copilot answer.

For B2B, this weighs more heavily than many people think. Microsoft 365 and Copilot sit deep in the work environment of business users, exactly the people you want to reach in their research and buying phase. A blind spot for Bing is therefore a blind spot for part of your business audience. Why AI visibility matters particularly in B2B we expand on in GEO for B2B, and the broader difference from classic optimisation you can read in GEO vs SEO.

What do you do to get cited in Copilot?

The quickest win is making sure your most important pages are visible in Bing, because without that foundation the rest of your content makes no difference. Only then does citability come into play: pages that an AI model reads easily, understands and finds trustworthy enough to show to its reader. Concretely, you take these steps. If you want everything in context, read getting found in Microsoft Copilot: the complete approach.

Check your visibility in Bing

Open Bing Webmaster Tools, add your site and check whether your core pages are indexed. Submit your sitemap and check whether there are crawl errors holding Bing back. This is the foundation: it takes little time and immediately reveals whether you are on the radar of the index Copilot draws from. If you cannot find your pages here, that is your first priority, before any content refinement.

Answer the question at the top of the page

Put the answer to the search question at the top and work out the nuance afterwards. A model scanning a page for a usable answer then finds within a few sentences what it needs. Long run-ups and vague introductions work against you. Write in clear, factual language and be specific, because concrete, verifiable statements are easier to cite than generalities.

Keep your content current and consistent

Copilot pulls fresh results, so pages that have been recently updated and are easy to find have an edge. Also make sure your brand name, services and facts appear consistently everywhere on your site and beyond. That helps every AI see you as one recognisable entity rather than as loose, contradictory fragments. To learn exactly how this works, read entity consistency and AI visibility.

An honest caveat belongs here. You do not buy a spot in a Copilot answer and no one can guarantee a citation. What you do do is systematically increase your chances by being findable, readable and trustworthy. At Customer Impact we therefore steer on what matters for your business, leads and revenue, not on isolated vanity figures. We are a small, fast senior team that would rather state a realistic limit than promise rankings no one can deliver.

The short summary

Microsoft Copilot chooses its sources via the Bing index. It translates your question into a Bing search query, reads a set of pages and cites from them. That is why your Bing visibility, not your Google position, determines whether you show up in Copilot. For marketers who only focus on Google, that is a blind spot. Start with Bing Webmaster Tools, make your core pages findable, and make sure your content answers at the top, is factual and stays consistent.

Want to know how findable your brand is in Copilot and other AI assistants right now, and what your first steps are? Take a look at our approach to AI visibility or book your free intake.