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Spreadsheet API for Developers

Convert and inspect Excel workbooks with sync /v1/sheets endpoints powered by exceljs. Transform XLSX to CSV/JSON and back, merge or split worksheets, and validate files — without Google Sheets dependencies.

Get API keyTry XLSX to JSONDocumentation

Features

What this API actually supports in production today.

  • xlsx-to-csv / csv-to-xlsx
  • xlsx-to-json / json-to-xlsx
  • xlsx-info and validate
  • merge-sheets and split-sheets
  • Sync responses for automation

Common use cases

  • ETL between CSV exports and Excel
  • API backends that accept spreadsheets
  • Normalizing partner data feeds

API endpoints

Base URL https://thefatbaby.com/api. Authenticate with Authorization: Bearer fb_live_YOUR_KEY.

MethodPathSummaryCredits
POST/v1/sheets/xlsx-to-jsonXLSX to JSON1 credit
POST/v1/sheets/xlsx-to-csvXLSX to CSV1 credit
POST/v1/sheets/csv-to-xlsxCSV to XLSX1 credit
POST/v1/sheets/json-to-xlsxJSON to XLSX1 credit
POST/v1/sheets/merge-sheetsMerge workbooks2 credits
POST/v1/sheets/validateValidate workbook1 credit

Examples

Primary endpoint /v1/sheets/xlsx-to-json · Most conversions are 1 credit; merge/split are 2.

cURL

curl -X POST https://thefatbaby.com/api/v1/sheets/xlsx-to-json \
  -H "Authorization: Bearer fb_live_YOUR_KEY" \
  -F "file=@workbook.xlsx"

JavaScript

const form = new FormData();
form.append('file', xlsxFile);
const res = await fetch('https://thefatbaby.com/api/v1/sheets/xlsx-to-json', {
  method: 'POST',
  headers: { Authorization: 'Bearer fb_live_YOUR_KEY' },
  body: form
});
const data = await res.json();

Python

import requests
r = requests.post(
  'https://thefatbaby.com/api/v1/sheets/xlsx-to-json',
  headers={'Authorization': 'Bearer fb_live_YOUR_KEY'},
  files={'file': open('workbook.xlsx','rb')},
).json()

Request

multipart/form-data
file=@workbook.xlsx
sheet=Sheet1  # optional

Response

{
  "rows": [ { "A": 1, "B": "x" } ],
  "credits_used": 1
}

Pricing & credits

Most sheet conversions cost 1 credit each.

View pricingStart free

Common errors

  • 400 — Invalid workbook or missing file
  • 402 — insufficient_credits

FAQ

Is this Google Sheets?

No. It converts Excel/CSV/JSON files via exceljs. There is no live Google Sheets OAuth integration.

Product hub?

See /sheets for the spreadsheets product overview.

Try without code

Use the matching online tool, then automate the same workflow with this API.

Try XLSX to JSONGet API key