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I received file with extension .ddoc instead of .xls or .xlsx.

So - what are .ddoc files? Are they even related to Microsoft Excel?

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up vote 3 down vote accepted

You're expecting a .xls or .xlsx file? That is an Excel 95/2000/XP file, or an Excel 2007/2010 file?

Google says .ddoc files are either: (1) DigiDoc Digital signature files (2) Digital Mars C, C++ or D files. Is it possible the sender mis-typed .ddoc in a Save As... command, when they might better have left Windows to add in the extension?

If you've not already, try changing the file extension to .xls (and/or .xlsx, .doc, or .docx ) then see if your recent version of Excel (or Word) opens it.

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There is an Estonian (and possibly neighbouring countries) digitally signed document format called DigiDoc that has a .ddoc extension. You can open such documents on this site:

Use Add Document to upload the doc for a 30 minute anonymous session. You can verify the signature, download and save the PDF, and see a Confirmation page verifying the document validity.

The format may be used for communicating official information with the Estonian authorities, and, in conjunction with an Estonian Smart ID card or Mobile ID if you need to sign your own documents.

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Could also be a MacDraw graphic file, according to a couple of File Extensions sites.

P.S. I built that website

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Its a digital document format which is assigned digitally by user. More information at:

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