I'm developing a prototype web application for Office365 using the SharePoint 2013 REST service.
I would preview Office document in browser before my application download it from Office365.
I found that Office365 used WopiFrame.aspx to preview Office document.
But I didn't find official reference for WopiFrame.aspx. Does anyone know it?
If it doesn't exist, please let me know any better way to preview Office document.

Thanks.

Hi,

Office 365 provides preview feature for Office document, because it has Office Web Apps Server up and running.

The URL format you are looking for is: <Site URL>/_layouts/15/WopiFrame.aspx?sourcedoc=<Doc URL>&action=default
We can use it directly.

Here are some articles for your reference:
http://paulryan.com.au/2013/link-to-open-in-browser-with-owa/
http://stevemannspath.blogspot.com/2012/10/sharepoint-2013-document-library-and.html
http://www.surfray.com/blog/2012/08/02/installing-the-office-web-apps-server-preview-for-sharepoint-2013/

Best Regards