The web app now runs inside a sandboxed structure (using IFRAME mode). Because the banner exists in a parent frame or a strictly protected DOM layer controlled by Google, your script's custom CSS cannot access or modify it due to security policies. Methods to Remove or Bypass the Banner

For a quick solution, you can install a browser extension that removes the banner. One such extension is “Google Apps Script WebApp Warning Remover” for Firefox. It simply hides the top warning on Apps Script web app pages.

If your software is designed strictly for organizational or business workflows, upgrading your architecture to a dedicated organizational tenant completely removes the banner for internal staff. Internal Execution Realities:

: Instead of the default project, create a new Google Cloud (GCP) project, associate it with your script, and go through the official OAuth verification process . Client-Side Workarounds (Developer/Internal Use)

The banner is a "price" of using the free consumer platform. If you use a paid Google Workspace

If you want to completely strip the banner, you cannot host the app on Google’s servers directly. Instead, you can use a "proxy" or a middle-man server.

If you are designing internal inventory tools, employee portals, or company automations, you do not have to look at the banner.

In the past, developers used custom CSS (like display: none !important on the banner's class or ID) or JavaScript DOM manipulation to hide the banner. Google patched this vulnerability.

) to prevent your code from accessing the parent page's elements, including the banner itself. Summary Table: Removal Options Difficulty iFrame Embedding Hides banner on the host site Google Sites Often suppresses banner for viewers Workspace (Internal) No banner for users in your domain GCP Verification Removes banner for public users linking to a GCP project Google Apps Script remove warning banner - Stack Overflow

account (Business or Education), you can deploy apps that don't show this warning to other users in your same domain. Internal Access: