OneDrive for Business alters files

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Why does OneDrive for Business change the Office documents and files you upload? has a worrying report on OneDrive for Business which appears to change the uploaded files. Microsoft seems to be adding information to customers uploaded files. We can’t find anywhere that discloses that and the reasons for it aren’t clear either.

When you upload a file to cloud storage you’d expect the copy you have and the copy on the cloud store to be exactly the same. No differences at all. As we’ll see, that doesn’t happen with OneDrive for Business.

The report only applies to OneDrive for Business (the new name for SkyDrive Pro). OneDrive, as used by most individuals seems unaffected. Office-Watch hasn’t been able to independently verify the report.

It seems that Word, Excel and PowerPoint documents uploaded to OneDrive for Business grew in size by around 8kb. That might not seem like much but there should not be ANY size difference.

Seán Byrne describes the changes in a test Word document:

There were two ‘.rels’ files and one XML file modified and three folders with files added – ‘customXml’ containing 6 XML files, a folder ‘_rels’ inside this containing three ‘.rels’ files and a ‘[trash]’ folder containing a ‘0000.dat’ file. In the ‘docProps’ folder, a file ‘custom.xml’ contains a property with a ‘ContentTypeId’ name attribute with a unique ID. …. I found the same ContentTypeID code inside as the Word file and while it matched, it was different to that in files I compared with other users”

Even more worrying is that the DateModified file attribute is not changed. So there’s no obvious clue that the document has been opened, changed and resaved.

It gets curiouser, a plain HTML file is also changed by OneDrive for Business. image from OneDrive for Business alters files at

Most likely this file is changed because HTML files can be opened and edited in Microsoft Word.

All this is very worrying. Document integrity is very important for both technical and legal reasons. Changing document content and hiding the fact by retaining the file date stamps is a major no-no, regardless of the reasons for it. Most likely Microsoft knows that, which is why these actions aren’t clearly disclosed to organizations paying for the service.

We’ve asked Microsoft for comment and we’ll let you know what they say.