Altair is a declarative data visualization library for Python based on the Vega-Lite grammar. It allows users to create statistical visualizations by mapping data fields to visual properties rather than writing imperative drawing code.
The library focuses on interactive charting through a system of linked selections and filters that update multiple visualizations based on user input. It renders charts as JSON and HTML for display in web browsers and interactive notebooks.
The project covers statistical data analysis and interactive data exploration, providing capabilities to export visuals as standalone HTML, JSON, or image files. These assets can execute directly within a web runtime to render charts without requiring a Python backend.