Need Help Previewing MS Office Documents (Word/Excel/PPT) in Browser via Appian Web API

Hi everyone,
We’re working on enabling document preview functionality in our Appian application. We created a Web API that can successfully preview and download documents from the UI.

However, we’re facing an issue specifically with Microsoft Office files (Word, Excel, PowerPoint).
Instead of previewing in the browser, these files automatically download.

Current behavior:

• PDF files preview correctly in the browser
• MS Office files (.docx, .xlsx, .pptx) always trigger a download, regardless of browser settings
• We are returning the document via a Web API using proper headers, but preview still doesn’t work

What we need help with:

• Is it possible to preview MS Office documents directly in the browser using Appian?
• Does Appian support inline preview of these formats, or do we need an external viewer (Office Online Viewer, Google Docs Viewer, etc.)?
• Any recommended approach, best practices, or sample configurations to achieve inline preview?