Here is my HTML file "Creds.html":

<form id="Creds">

  Client ID: <input id="id" type="text" width="45"><br>

  Client Secret: <input id="secret" type="password" width="45"><br>

  <input id="submit" type="button" value="Submit" width="15" onclick="google.script.host.close()"><br> 


Here is the Google Sheets bound Apps Script that is attempting to display it:

function setCreds () {

  var ui = SpreadsheetApp.getUi();
  var form_cred = HtmlService.createHtmlOutputFromFile('Creds');

  //var newcreds = ui.showSidebar(form_cred);
  var newcreds = ui.showModalDialog(form_cred);

The .ShowSidebar line works when I switch the // comment line. However, the .showModalDialog line gives the following error:

Exception: The parameters (HtmlService.HtmlOutput) don't match the method signature for Ui.showModalDialog.

Why am I getting this error? What needs to change?

  • NOTE: The HTML headers in the HTML file were removed from my HTML code above when I submitted this question, even though I pasted them in. They are there in my file.
    – Trashman
    Feb 15, 2022 at 1:24

1 Answer 1


showModalDialog requires a title. Doc ref

Change: var newcreds = ui.showModalDialog(form_cred)

To: var newcreds = ui.showModalDialog(form_cred,"title")

  • I should have checked the documentation closer. In my defense, the error generated is not helpful to solving the problem. If nothing else, hopefully this question/answer is an easy to find solution for anyone else having the same problem.
    – Trashman
    Mar 3, 2022 at 15:49
  • To be fair, error messages are rarely helpful. But Google is your friend. It's good to remember when anything error occurs that it's almost certain that it has happened to someone else before.
    – Tedinoz
    Mar 3, 2022 at 22:58

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