Citations in responses

Citations is a feature that allows Claude to ground its responses in specific source documents or web pages by providing verifiable references to the exact text passages it used to generate an answer. When enabled, Claude automatically identifies which claims in its output are drawn from provided sources and attaches precise references — including exact quoted text and its location — so users can verify the information independently. There are two distinct modes of citations. In the claude.ai web interface, citations are tied to the Web Search tool: when you enable web search and Claude queries the internet, it appends numbered inline links (e.g., [1], [2]) to relevant sentences, pointing to the source URLs. In the API, citations work with user-supplied documents (PDFs, plain text, or custom content blocks): developers set a flag on each document, and Claude returns structured JSON that includes the exact quoted text and character-level location within the source file. The primary purpose of citations is to reduce hallucinations and make Claude's outputs auditable. Instead of trusting Claude's answer at face value, users and developers can trace every factual claim back to a specific sentence or paragraph in a real source document or webpage.