Does Microsoft Copilot hallucinate? What the data shows
Last updated: July 26, 2026
Yes. Microsoft Copilot hallucinates despite grounding its answers in Bing and your enterprise data. In the March 2025 Tow Center study, Copilot gave incorrect answers on a majority of tested queries, and a 2025 Cambridge legal study found it produced hallucinated legal content on about 26% of answers despite RAG. Retrieval-augmented does not mean verified.
Does Copilot hallucinate, and how often?
Yes, Microsoft Copilot hallucinates, even though it is grounded in Bing search and, in enterprise settings, in your own Microsoft 365 documents. Grounding lowers the rate; it does not remove the failure.
Independent testing shows the gap. In the Tow Center / Columbia Journalism Review study (March 2025, eight AI search engines, 1,600 queries), Copilot was among the engines that answered incorrectly on a majority of queries (CJR, 2025). And the 2025 Cambridge legal study (50 legal questions, Dec 2024–Apr 2025) found Copilot produced hallucinated legal content on about 26% of answers despite RAG — the paper explicitly concludes RAG is not the driving force behind accuracy and did not resolve hallucination (Cambridge IJLI, 2025).
Grounding raises the floor, not the ceiling
Copilot's Bing and Microsoft 365 grounding genuinely reduce pure invention — that is a real strength. But grounding a model in retrieved documents does not guarantee the answer faithfully represents them. The last mile — does the sentence match the source? — still fails, especially on documents outside the retrieved set.
Copilot's signature failure: confident answers beyond the retrieved documents
Copilot's most characteristic failure in enterprise use is answering confidently about content its grounding did not actually cover — filling the gap with fabrication that inherits the authority of your trusted Microsoft 365 environment. Because it sits inside Word, Outlook, and Teams, users extend more trust to it than to a standalone chatbot.
Worked example. In Microsoft 365 Copilot, ask "summarise our refund policy for enterprise contracts." Your document library has a general refund policy but nothing enterprise-specific. Copilot retrieves the general policy, then confidently states an enterprise carve-out — a 60-day window, an approval tier — that appears in none of your documents. The answer is formatted like an internal citation and lands in a Teams channel as fact. The grounding was real but incomplete, and Copilot papered over the gap.
How to fix Copilot hallucinations: manual and automated
The fix for Copilot is to check its answers against the actual source documents, and to be most careful exactly where its enterprise integration makes it feel most trustworthy.
Manual checks:
- Open the documents Copilot cites and confirm they contain the specific claim, not just the general topic.
- Be alert when Copilot answers a question your document set does not clearly cover — that gap is where it fabricates.
- For legal, HR, or financial answers, route Copilot output to human review before it becomes an action or a policy statement.
Automated with Mephistopheles: paste any Copilot answer into /chat, or use the de-identify-then-verify path for sensitive internal content — it strips identifiers before any external grounding. Mephistopheles returns a per-claim verdict and a hallucination-risk score, flagging claims your source set does not support. On our ~290-claim benchmark it catches ~88% of factual errors and passes ~98% of true statements clean (~2% false-alarm rate).
Frequently asked questions
Doesn't Bing grounding stop Copilot from hallucinating?
No. Bing grounding reduces pure invention by retrieving real pages, but Copilot can still misrepresent what those pages say, or fabricate to fill gaps its retrieval did not cover. The 2025 Cambridge legal study found Copilot hallucinated on about 26% of answers and concluded RAG did not resolve hallucination. Verify the specific claim against the source.
Is Microsoft 365 Copilot safe for internal documents?
It is useful but not self-verifying. Copilot can confidently answer about topics your document set does not actually cover, producing fabrications that inherit the trust of your Microsoft 365 environment. Check its answers against the source files, especially for policy, HR, legal, and financial questions.
Why does Copilot make up things that aren't in our files?
When your documents don't contain the answer, Copilot may still respond confidently, blending retrieved fragments with invented specifics rather than saying it doesn't know. The gap between what it retrieved and what you asked is where fabrication appears. Watch for answers on topics your files don't clearly cover.
How do I verify a Copilot answer safely?
Paste it into Mephistopheles, using the de-identify-then-verify path for sensitive internal content so identifiers are stripped before external grounding. It returns per-claim verdicts and a risk score, flagging claims your sources don't support.
Verify what your AI just told you.
Paste any AI answer and Mephistopheles checks each claim against independent sources — no sign-up to try.