Infinite canvas tools are a way to view and organize information spatially, like a digital whiteboard. Infinite canvases encourage freedom and exploration, and have become a popular interface pattern across many apps. The JSON Canvas format was created to provide longevity, readability, interoperability, and extensibility to data created with infinite canvas apps. The format is designed to be easy to parse and give users ownership over their data. JSON Canvas files use the .canvas extension.

Source: JSON Canvas — An open file format for infinite canvas data.