Last reviewed: November 5, 2026.
An AI hallucination is when a chatbot states something false in a confident, believable way. It might invent a statistic, a quote, a book, or a web link that does not exist. This happens because language models predict likely words, not verified facts. The good news is that you can catch most hallucinations with a few habits.
Why hallucinations happen
A chatbot has no built-in fact checker. It writes the answer that seems most plausible based on patterns in its training data. When it does not know something, it often fills the gap with a smooth guess instead of saying "I don't know." Newer tools reduce the problem, especially when they search the web and show sources, but no tool has removed it.
Red flags to watch for
Very specific details with no source: exact percentages, dates, page numbers, or quotes.
Links that do not work: always click them.
Names of studies, books, or experts you cannot find with a quick search.
Answers that sound too perfect for a question that is actually debated or unclear.
Confidence that does not change when you ask "are you sure?"
A five-step check
Pick the claims that matter most, such as numbers, names, and anything you plan to repeat.
Search for each claim on a trusted source, such as a textbook, a government or university site, or a respected news outlet.
Ask the AI for its sources, then open them and confirm they say what the AI claims.
Ask a second AI tool the same question and compare the answers.
If you cannot confirm it, leave it out or label it as unverified.
Prompts that help
"If you are not sure, say so instead of guessing."
"Give me sources I can open, and tell me which claims you are least sure about."
"List what you know for certain and what you are inferring."
These prompts do not make an AI always right, but they make guessing easier to see.
Practice it
Our free Intro to AI course has a full lesson on checking AI answers, and our guides to ChatGPT, Gemini, and DeepSeek cover each tool's quirks.
Sources: general guidance on large language model limitations from OpenAI, Google, and Anthropic product documentation.
