Custom app is not loading

Brass Contributor

Hi everybody,


our Web-Application does work in the MS-Teams Client version but it does not work anymore since update the MS Teams client to version

The application still works in the browser, but in the MS Teams custom tab we see following error within the Dev Tools console log:



Any ideas what has changed in MS Teams version







3 Replies

@relkniw - The page that loaded by iframe returned this error. The X-Frame-Options HTTP response header can be used to indicate whether or not a browser should be allowed to render a page in a <frame><iframe><embed> or <object>. Sites can use this to avoid click-jacking attacks, by ensuring that their content is not embedded into other sites.

Ensure that you adhere to the following prerequisites while building your Teams personal and channel or group tab:

  • Allow your tab pages to be discovered in an iFrame, using X-Frame-Options and Content-Security-Policy HTTP response headers.

    • Set header: Content-Security-Policy: frame-ancestors * *
    • For Internet Explorer 11 compatibility, set X-Content-Security-Policy.
    • Alternately, set header X-Frame-Options: ALLOW-FROM This header is deprecated but still accepted by most browsers.

Ref: Prerequisites - Teams | Microsoft Learn


Can you give me further information where I have to configure that for a web application hosted on IIS?

And what has changed in MS Teams that this failure occours? Because the application works fine in .