Knowbase is a ChatGPT-powered knowledge base where you can upload various files to the repository and then access them through chat with ChatGPT. You can upload PDFs, MP4, MP3, TXT, PPTX, DOCX, DOC, and YouTube videos. Knowbase supports multiple languages, including English, Chinese, French, German, and more. You can try Knowbase with the free plan, which offers 100MB of storage space and 10 questions per month.