Typically, we see Office Web Apps Server 2013 paired with a SharePoint 2013 environment. 

However, customers are free to use Office Web Apps Server 2013 with any product which can act as a WOPI (Web application Open Platform Interface) host.

This means, if customers do not want to use SharePoint 2013 to host their files, and they still want to use Office Web Apps, they can!

SharePoint 2013 uses the [wopiframe.aspx] page to communicate with Office Web Apps Server 2013.  This is a SharePoint 2013 hosted page which gives the appropriate web app a place to display content.

Non-SharePoint WOPI hosts use the [view.aspx] page to display the web apps.  This is an Office Web Apps Server 2013 hosted page.

If you're using SharePoint 2013, or any other file hosting solution, chances are you have a lot of files, some of which are large.

Office Web Apps Server 2013 has the ability to let you to adjust the size of Excel files displayed in the web apps.  This is a farm setting called [ExcelWorkbookSizeMax]; the number displayed is in MB.

Please be aware that while the following information may resolve your issue, it is not a solution supported by Microsoft.

When adjusting the [ExcelWorkbookSizeMax] value, the settings will only apply to the [wopiframe.aspx] page.  Obviously this is an issue if you are using a non-SharePoint solution which utilizes the [view.aspx] page.

We looked at this problem from a couple perspectives, and here's what we found.

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1. Since we know non-SharePoint WOPI hosts call [view.aspx], rather than [wopiframe.aspx], is there a way to somehow replace [view.aspx] with [wopiframe.aspx]? 

No. Through extensive testing we found there is no way to modify or replace the [view.aspx] page to force it to behave like the [wopiframe.aspx] page.

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2. Are there any other modifications we can make to the Office Web Apps server to get it to display large documents?

Yes. There are modifications we can make to portions of IIS on the Office Web Apps server.

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Instructions to modify IIS on the Office Web Apps server...

1. In IIS on the Office Web Apps server, you will find a number of directories under the HTTP80 site.  We are looking specifically for the /oh and the /op directories.

2. Open each of these directories in explorer view and you will find a web.config file and a Settings_Service.ini file.

3. Open the Settings_Service.ini file in Notepad.

4. Add "OpenFromUrlMaxFileSizeInKBytes=(System.Int32)500000" to the end of the ini file.  It should look like this...

5. Make sure to update the Settings_Service.ini file in both the /oh and /op directories.

6. Make sure the value in KB, matches the Office Web Apps farm setting in MB.

For this example, we are using 500,000 kilobytes, so the Office Web Apps farm setting would be 488 MB.

Please be aware that this size setting will apply to ALL Office document types in the web apps, not just Excel.