How can I clear metadata (personal data) from an Excel file in Microsoft 365 for macOS?

Question

I want to make sure that an Excel file I created is purged of all personal and user metadata before passing it on, for confidentiality reasons.

For Windows, there are many guides for removing personal metadata from most Office data files.

Example guide direct from Microsoft:
https://support.office.com/en-us/article/remove-hidden-data-and-personal-information-by-inspecting-documents-presentations-or-workbooks-356b7b5d-77af-44fe-a07f-9aa4d085966f

I have also found guides for removing metadata from Microsoft Word specifically on MacOS:
https://support.cu-portland.edu/hc/en-us/articles/360011611633-Scrub-metadata-from-Word-documents

In short, most approaches to removing metadata from Office files in Windows involve the use of the built-in Document Inspector, which doesn't seem to exist in the MacOS versions of Office apps. There does seem to be a way to purge metadata from a Microsoft Word file in MacOS (Tools -> Protect Document -> Check "Remove personal information from this file on save"), but there doesn't seem to be any equivalent for Microsoft Excel.

I am running the latest version (at the time of this posting obviously) of Microsoft Office 365 and Microsoft Excel 16.36 (20041300) for MacOS Catalina 10.15.4.

^{Note, I wasn't 100% sure where to post this. I consulted a StackExchange question (https://meta.stackexchange.com/questions/90919/which-stack-exchange-site-is-best-for-microsoft-excel-questions) which said that I should use the SuperUser stack for Microsoft Office related questions, but since this is an Office question that is specific only to the MacOS version, I decided it would be more appropriate here. It seems to me, though, that an Office-specific stack might be useful.}

Answer 1

I can't speak to how well this works, but if you go to Excel > Preferences > Security, there's a checkbox that says "Remove personal information from this file on save."

Answer 2

.xlsx files are secretly zip files, containing mostly .xml files.

When I unpack a spreadsheet file as a zip file and search for my name in the output, I find that docProps/core.xml seems to be where the metadata is stored, e.g.,

<?xml version="1.0"?>
<cp:coreProperties xmlns:cp="http://schemas.openxmlformats.org/package/2006/metadata/core-properties" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:dcmitype="http://purl.org/dc/dcmitype/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <dc:creator>••My Real Name••</dc:creator>
    <cp:lastModifiedBy>••My Real Name••</cp:lastModifiedBy>
    <dcterms:created xsi:type="dcterms:W3CDTF">2022-07-05T13:53:14Z</dcterms:created>
    <dcterms:modified xsi:type="dcterms:W3CDTF">2022-07-05T13:53:14Z</dcterms:modified>
</cp:coreProperties>

If you’re comfortable using the command line, deleting that particular .xml file entirely from the .xlsx file with:

zip -d foo.xlsx docProps/core.xml

seems to be enough to make excel not show that info any more in the File → Properties… dialog.

I’m not an excel forensics expert so I can’t guarantee that there’s no other encoded metadata hanging around, but this should be enough to deter casual snooping.