I am trying to open in Office 365 MS Word documents from the 1990s. It doesn't let me.

Use Word for Mac’s Recover Text option to extract each legacy document, then immediately save the recovered copy as a new .docx file.^1^

Before proceeding, duplicate the original files in Finder and work only with the copies. Do not overwrite or discard the originals; text recovery or conversion can change formatting.

Recover the document in Word

1. Open Word without opening the old document.
2. Select Word > Preferences.
3. Under Authoring and Proofing Tools, select General.
4. Enable Confirm file format conversion at Open, then close Preferences.
5. Select File > Open.
6. Select the copied legacy document once.
7. In the Open menu near the lower-right corner, select Recover Text, then select Open.
8. Accept the warning if one appears.
9. Check the recovered content carefully. Some formatting, images, tables, footnotes, or other non-text elements may change or be lost.
10. Select File > Save As, choose Word Document (.docx) under File Format, and save it under a new name.^2^

Repeat this separately for each document rather than batch-processing irreplaceable files.

If Recover Text does not work

Try these alternatives in order:

1. Update Word
   • In Word, select Help > Check for Updates.
   • Install all available Office updates and retry File > Open > Recover Text.^1^
2. Convert a copy through OneDrive
   • Sign in to OneDrive in a browser.
   • Select Upload and upload a copied document.
   • Select the uploaded file and allow OneDrive to convert it.
   • Select File > Save as > Download a copy.
   • Save the resulting file to the Mac, then verify its contents before deleting anything.^1^
3. Use Apple TextEdit or an older Word installation
   • In Finder, Control-click a copied file and choose Open With > TextEdit.
   • This may preserve readable text with only basic formatting.
   • If an older, compatible version of Word is available, open the copy there and save it in a newer format. Microsoft lists both approaches for legacy files blocked by current Word for Mac.^1^

If none of the copies can be opened

The files may be damaged rather than merely blocked. Retrieve another copy from Time Machine or another backup and repeat the recovery procedure on that copy.^1^

The Windows instruction sometimes suggested—Trust Center > File Block Settings—does not apply to Word for Mac. Avoid third-party online converters for confidential documents unless their privacy and retention terms are acceptable.

References

1. Error: [Filename] uses a file type that is blocked from opening in this version | Microsoft Support
2. Recover files in Office for Mac