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Excel to JSON converter

Turn an Excel sheet into JSON. Pick the sheet, keep the dates readable, and your workbook never leaves your browser.

Works with
XLSXCSVJSONJSONL

Drop an Excel or CSV file here

CSV, TSV or .xlsx, up to 100 MB. It stays on your computer.

  • No sign-up
  • Nothing uploaded
  • Any sheet in the workbook
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  • Bacardi logo
  • British American Tobacco logo
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  • Golden Acre logo
  • Handlangers logo
  • Inspired Learning Group logo
  • Kantar logo
  • MUFG logo
  • NielsenIQ logo
  • PTI Digital logo
  • RethinkFirst logo
  • Starbucks logo
  • The Specialist Works logo
What you get

Your sheet as JSON, dates and all.

  • Your workbook stays on your computer

    The .xlsx is opened in your browser. Nothing is sent to Mammoth or anyone else.

  • Any sheet, not only the first

    A workbook with several tabs gets a Sheet menu, so you can convert Orders, then Returns, without opening Excel.

  • Dates you can read

    A date cell becomes 2026-11-01, not the 46327 Excel stores. Numbers and TRUE/FALSE keep their types.

How it works

How to convert Excel to JSON

The first row of the sheet gives the keys and each row below it becomes one object.

  1. 1

    Add your workbook

    Drop an .xlsx file on the box or choose one. CSV works too.

  2. 2

    Pick the sheet

    Switch sheets from the menu, and choose an array or JSON Lines.

  3. 3

    Download or copy

    Save the .json file, or copy it into your code.

Your options

Other ways to do it

Excel has no Save as JSON. These are the usual ways round it.

  • Python with pandas

    A job you script once

    • Readable datesYes
    • Pick any sheetYes
    • No code or installNo
    • Runs on a scheduleYes

  • Office Scripts in Excel

    Excel for the web users

    • Readable datesYes
    • Pick any sheetYes
    • No code or installNo
    • Runs on a scheduleYes
  • This page

    This converter

    One-off files, no setup

    • Readable datesYes
    • Pick any sheetYes
    • No code or installYes
    • Runs on a scheduleNo
Other ways

How to convert Excel to JSON without a converter

Excel can't save a sheet as JSON. In Excel for the web, an Office Script can write a table out as JSON; Microsoft publishes a sample. In Python, pandas reads the workbook and writes JSON in two lines.

In Excel for the web, with Office Scripts:

  1. 1

    Format the data as a table (Insert > Table).

  2. 2

    Open the Automate tab and choose New Script.

  3. 3

    Paste Microsoft's “Output Excel data as JSON” sample and run it. The JSON appears in the script's output.

Only need a CSV? The CSV to JSON converter takes the same steps for .csv files.

Python with pandas
import pandas as pd

df = pd.read_excel("orders.xlsx", sheet_name="Orders")
df.to_json("orders.json", orient="records", date_format="iso", indent=2)

read_excel needs the openpyxl package installed. date_format="iso" writes dates as text instead of milliseconds.

Your file stays private

The converter runs inside this page. Your workbook is opened and written out as JSON on your computer, and nothing is sent to Mammoth. That makes it safe for sheets with customer or salary data in them.

How we handle your data

Once the page has loaded, it works with your internet switched off.

Every month

Getting the same workbook every month?

Mammoth can take it from there. Put each month's workbook in a folder and the rows are added to one table, ready to download as JSON.

Try Mammoth free

Monthly workbooks

Septembersales-sep.xlsx
Octobersales-oct.xlsx
Novembersales-nov.xlsx
DriveDropboxOneDriveSFTP
All monthsUp to date
Sep 30North41,200.00
Sep 30South38,755.50
Oct 31North43,880.10
Oct 31South37,020.00
Nov 30North45,115.75

Illustration. Every new file in the folder is added to the same table.

Questions

Excel to JSON questions

Is my workbook sent anywhere?
No. The page opens the .xlsx file and writes the JSON inside your browser. Once the page has loaded, it works with your internet switched off.
Which sheet is converted?
The first visible sheet. When the workbook has more than one, a Sheet menu appears above the result so you can switch. Hidden sheets are left out.
What happens to dates?
Excel stores a date as a number of days, so 1 November 2026 is 46327 inside the file. The converter reads each cell's date format and writes 2026-11-01 instead, or 2026-11-01T09:30:00 when the cell has a time.
Which row gives the keys?
The first row with anything in it. Empty rows above the table are skipped, a blank header becomes column_1, column_2 and so on, and a repeated header gets _2 added so every key is unique.
Are formulas kept?
The JSON holds each formula's last calculated value, the number or text you see in the cell. The formula itself is not part of the output.
Does it read .xls files?
Not the old .xls format from Excel 2003 and earlier. Open the file in Excel and save it as .xlsx or CSV first.
Can I get nested JSON?
Yes. Headers with a dot, like customer.name and customer.country, become one customer object. Turn off Nest dotted columns to keep them flat.
Is there a size limit?
Workbooks up to 100 MB.
Is it free?
Yes, with no account and no email.

More free tools

Free toolCSV to JSONThe same converter for CSV files.Take a lookFree toolJSON to ExcelTurn JSON back into an Excel file.Take a lookFree toolMerge Excel filesCombine several workbooks into one.Take a look