AI for Document Q&A with Source Citations

Live demo: https://doculens-evidence.vercel.app

DocuLens is a document question-answering application. It extracts text from supported formats, retrieves relevant passages and presents answers alongside source references. It emphasises evidence traceability and clear handling of questions the document cannot answer.

AI answers about documents are hard to trust when you cannot see where they came from.

Upload a PDF or text file and ask a question. Every answer links to the exact passage, and the quoted sentence is highlighted in the document viewer.

PDF and text upload with size, type and content validation; clear errors for scanned or malformed PDFs (no OCR is claimed)

Passage chunking with page or line numbers; BM25 retrieval with an evidence threshold

"Insufficient evidence" responses instead of guesses

Optional AI answers whose citations are verified against the retrieved text; the live demo uses quote-based answers, labelled as rule-based

Citation inspection with highlighting, copy, Markdown export and clear document

In-memory processing (nothing is stored on the server); document text is treated as untrusted data; tests generate real PDFs. 37 unit/integration tests and 10 browser tests (desktop and mobile).

No OCR. Keyword retrieval can miss answers phrased differently from the question. Files are limited to 4 MB and 200 pages.