Markup is an online annotation tool that transforms unstructured documents into structured formats. Powered by GPT-4, it simplifies the process of creating structured datasets from free text, facilitating various NLP and ML tasks such as named-entity recognition. Markup supports a variety of file types, including PDFs, images, and web pages, allowing for versatile document annotation. It is designed to save time and improve accuracy in data preparation, making it an essential tool for data scientists, researchers, and developers.