When is Excel to JSON useful?
Excel to JSON is the conversion that turns a spreadsheet maintained by hand into data a program can consume. A price list, a translation table, or a list of test cases usually lives in a workbook because that is where people can edit it comfortably, and then has to become JSON for an application. This page reads the first worksheet of an XLSX file in the browser: the package is decompressed with the browser's own stream support, the worksheet XML is parsed, and each data row becomes one object with the header row as its keys.
The first row is the header. Each cell in it becomes a key, and an empty header becomes column_1, column_2, and so on, so a sheet with a gap in the header still produces usable keys. Each later row becomes one object. Values are typed by a narrow rule: a cell becomes a number only when the text is a plain number, so 114 becomes 114 while 007 stays the string 007, because turning it into a number would drop the leading zero. A decimal such as 12.50 becomes 12.5, which is the same value written more briefly, and a date such as 2026-10-22 stays a string because it is not a plain number. A true or false cell becomes a boolean, an empty cell becomes an empty string, and everything else stays a string.
The reader is intentionally small. It reads stored values, so a formula whose cached result is missing arrives empty, and it does not follow other worksheets, charts, merged ranges, or cell formatting. Each cell is placed by its own column reference, so a gap in the middle of a row stays a gap and the columns after it keep their place. Rows where every cell is empty are skipped. For a workbook that holds personal data, remember that the JSON is produced in the tab and the file itself is never uploaded.