Migrated files much larger in SharePoint Online than on disk

New Contributor

I am doing some migration testing and I am surprised how much larger files are when uploaded to SharePoint Online. I uploaded roughly 80GB of office files, which resulted in maxing out the storage limit I had set for the sitecollection at 200GB. Some files are triple their original size and I have checked there is only one version. The "storman.aspx" also reports larger size than the Version history. The files were uploaded using a SPOMigrationPackage. Any ideas why the files are so much larger?

10 Replies
From where are you uploading your files: File System? Of course this is not normal behavior and it's totally unexpected

Yes it is from the local file system.

I have seen file sizes change (http://techtrainingnotes.blogspot.com/2010/11/sharepoint-changes-files-as-they-are.html), but nothing like that. Any unusual files types?


I wonder if you had some ZIP files unpacked in the move?


No it was just standard test office files. I used Invoke-SPOMigrationEncryptUploadSubmit to migrate the files. 


Here are some examples:










Have you also checked the number of files in the Doc. Library is the same number you have in your local disk? I would also review if there are any checked out files in the doc. libary...as you said, it seems each files has only a version but you have many files there so not sure if this is true for all the files

Yes I have checked that the nr of files and folders match.

Small increases (e.g. 10 kB for msg files) are expected but this is extreme.
I have only seen this increase for compressed tiff files where the size sometimes increases 5 folder upon uploading (SharePoint uncompresses the tiff, inserts metadata and then applies a much less efficient compression mechanism).
I would compare the contents of the pptx before and after uploading. rename the extension to zip and then unpack the file. This should provide information what is going on.


I have discovered the exact same issue... 200kB word docs have grown after sharepoint upload to 1.4MB files! There are no extra 'versions' that I can see, just the document itself; It is exactly as you have shown. I uploaded simply by syncing a folder on my desktop to the site library.

Did you happen to find out what is going on?

@Håvard Meling did you ever find a solution to this issue?  I am having exactly the same problem and can't find a solution.  I have just migrated all our data across to SharePoint - just normal Office files in Word and Excel, PDF files and some images.  Almost every file I uploaded has a much bigger file size online than it does on the local disk.  I have a backup/synch application that I wanted to use to keep an offline backup but when I analyse changes between my locally synched SharePoint sites with the original files on a hard disk, they are all same dates/times/names - but totally different file sizes.  Any pointers you can give to an explanation greatly appreciated.

did you compare a file before and after uploading?
For Office files I would simply open the file with a zip tool to see the different components (e.g. xml files, images, ...). For binary files I would suggest to use the online tool https://hexed.it/

Some small changes are expected for msg and Office files but they should be in the order of 10 kB's.

Paul | SLIM Applications