Send responses to Google Sheets

1. Open the Google Sheet where you want responses to land.
2. Click Extensions → Apps Script. Delete anything in the editor and paste the snippet below.

function doPost(e) {
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  var data = JSON.parse(e.postData.contents);
  var headers = sheet.getRange(1, 1, 1, Math.max(1, sheet.getLastColumn())).getValues()[0];
  if (!headers[0]) {                       // first run: write a header row
    headers = Object.keys(data);
    sheet.appendRow(headers);
  }
  var row = headers.map(function (h) { return data[h] != null ? data[h] : ''; });
  sheet.appendRow(row);
  return ContentService
    .createTextOutput(JSON.stringify({ ok: true }))
    .setMimeType(ContentService.MimeType.JSON);
}

1. Click Deploy → New deployment and choose type Web app.
2. Set Execute as: Me and Who has access: Anyone, then Deploy and authorise.
3. Copy the Web app URL — it ends in /exec.
4. In Formspry open your form → Automations → Google Sheets, paste the URL, and Save.