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Excel to JSON

Drop an .xlsx or .csv, pick the sheet, and get JSON — one object per row by default, or an array of arrays, or one array per column. Numbers and booleans are typed; reference numbers with leading zeros stay strings. No macro, no add-in, and the workbook is never uploaded.

Your workbook

Drop .xlsx, .xlsm or .csv here, or click to choose

Nothing is uploaded. The file is read by JavaScript in this tab and never leaves your computer — no server sees it, and closing the tab throws it away.

How to convert an Excel file to JSON

Drop the workbook. A .xlsx with several sheets shows a sheet picker; the sheet you choose is the one that converts.
Say whether row one is a header. With a header, its cells become the JSON keys. Without one, the spreadsheet letters A, B, C are used.
Pick a shape. Objects for an API or a script, arrays to keep column order compact, columns for a dataframe.
Copy or download. Copy the JSON straight into your editor, or download a .json file.

What the workbook gives up on the way out

JSON has values, not a spreadsheet. Three things do not survive, and it is better to know which:

Formulas become their results. An .xlsx stores the last value Excel calculated alongside the formula; that cached value is what you get. A workbook saved by a tool that never calculated the formulas will have blanks there — open it in Excel once and save it.
Formatting is not data. Currency symbols, colors and column widths are display, and they are dropped. A cell displaying €8,600.00 comes out as the number it holds.
Merged cells un-merge. The value lives in the top-left cell of the merge; the others are empty. That is what the file says, and guessing otherwise would invent data.

Dates

Excel stores dates as numbers with a display format. Cells formatted as dates are read back as dates and written as text in the form the sheet showed, rather than as the serial number — a bare 45914 in your JSON is a bug nobody catches quickly.

Which sheet, and what about the rest

One sheet converts at a time, and the picker lists every sheet with its row count so you can tell which is which. Hidden sheets are listed too — workbooks often keep the real table on one.

Doing it repeatedly

TableDI 2 is a desktop app for file work you redo every period: it keeps your sources, rules and delivery as a job, so next month you drop in the new files and run it again. Everything runs on your own machine.

Questions people ask

Do formulas convert, or only their results?

Their results. An .xlsx stores the value Excel last calculated for each formula cell, and that is what is read. If a file was written by a program that never calculated the formulas, those cells are blank — open the workbook in Excel or LibreOffice once and save it, and the values will be there.

What do dates come out as?

As the text the sheet displayed, not Excel's internal serial number. Cells that are numbers merely formatted to look like dates are a real ambiguity in spreadsheets; what the cell is formatted as is what is used.

Can I convert several sheets at once?

Not in one pass — pick a sheet, convert, pick the next. Each sheet usually has different columns, so a single combined JSON document would need a wrapper whose shape only you can choose.

Are my files uploaded anywhere?

No. The file is read by JavaScript running in this tab, using the browser's own DecompressionStream to unzip .xlsx and a parser that runs on your machine. There is no server call in the page — you can watch the network tab while you use it. Close the tab and the data is gone.

Does it work with old .xls files?

Not directly. The .xls format is a different, binary format from Excel 97. Open it in Excel, LibreOffice or Numbers and save as .xlsx or .csv, then come back. The tool tells you this rather than failing silently.

Why are some numbers strings?

Leading zeros and values too long for a JavaScript number stay strings, because converting them would change them. Everything unambiguous is typed.

Doing this every month?

TableDI 2 keeps it as a job — the files, the key columns, the tolerance and the fixes you made. Next month you drop in the new files and run it again.

Download TableDI 2 free See what's free

macOS, Apple silicon and Intel; Windows is in progress. Free is not a trial — no account, no card.

Last reviewed 2026-09-15 by the TableDI team. Something wrong on this page? Tell us — it is one inbox, read by the people who build TableDI.