I’m working on creating a Google Sheets add-on that connects to an external service through OAuth 2.0 authentication. I’ve successfully implemented the OAuth flow as a standalone web application, but now I need to integrate it properly into my add-on interface.
Currently I have:
- A custom menu in Google Sheets with an authentication option
- Working OAuth process that functions when accessed directly via URL
- The challenge of connecting these two components seamlessly
I attempted to load the external OAuth dialog into a sidebar but encountered issues. What’s the recommended approach for displaying third-party OAuth dialogs within Google Sheets add-ons? Can I trigger an external authentication popup through Apps Script, or should I use a different method?
Any guidance on best practices for handling external API authentication in Google Workspace add-ons would be appreciated. I want to ensure users have a smooth authentication experience without leaving the spreadsheet environment unnecessarily.
What I found effective after struggling with the same issue was using Google’s UrlFetchApp in combination with a sidebar approach. Rather than fighting against the sandbox restrictions, I built a workflow where the sidebar contains a simple button that opens the OAuth provider’s authorization URL in a new browser tab using window.open(). The trick is setting up your OAuth redirect to point to a lightweight web app you deploy separately using Apps Script’s web app functionality. This web app captures the authorization code and stores it temporarily with a unique session identifier. Meanwhile, your sidebar polls your web app endpoint every few seconds to check if authentication completed. Once detected, it retrieves the tokens and closes the polling loop. This method respects Google’s security model while maintaining user experience. The authentication happens in a proper browser context where third-party cookies work correctly, avoiding many of the common OAuth pitfalls in restricted environments. Just remember to implement proper timeout handling and clear any temporary data after successful authentication.
I’ve dealt with similar OAuth integration challenges in my add-on projects. The key insight I discovered is that Google Apps Script’s HtmlService is your best friend for this scenario. Instead of trying to embed external OAuth dialogs directly, create an HTML dialog that hosts your OAuth flow within the add-on’s context. What worked for me was building a modal dialog using HtmlService.createHtmlOutputFromFile() that contains the OAuth initiation logic. The dialog can open the external OAuth provider in a new window while maintaining communication back to your add-on through google.script.run. Once authentication completes, you can capture the authorization code or tokens and pass them back to your Apps Script backend. One crucial point: ensure your OAuth redirect URI points to a simple HTML page that can communicate with the parent dialog. This approach keeps users within the Sheets environment while still providing proper OAuth security. The authentication window closes automatically after successful completion, creating that seamless experience you’re looking for.
oauth in add-ons can be tricky but doable. I used ScriptApp.newAuthorizationUrl() method to generate auth urls and then displayed them in a simple html dialog. the user clicks the link, auths externally, then you handle the callback. make sure your redirect url is whitelisted in your oauth app settings or it wont work properly.