Two shapes: array of objects ([{"a":1,"b":2}, ...]) where object keys become column headers, or array of arrays ([[1,2],[3,4]]) where each inner array is a row.

With "Flatten nested objects" enabled, {"user":{"name":"X"}} becomes column user.name. Without flattening, nested objects are stringified as JSON inside a single cell.

The tool collects all unique keys across all objects and creates a column for each. Missing values in a given row are left empty in the spreadsheet.