What Is a .WBK File?
Word left a .wbk file next to your document and you want your text back. It is Word's automatic backup copy. Here is how to open it and recover your work.
What a WBK file is
A .wbk file is a Word backup document. When you turn on Always create backup copy in Word's options, each time you save, Word keeps the previous version as Backup of <name>.wbk in the same folder. If your .docx is lost or corrupted, the .wbk holds the last-but-one version.
How to open it
In Word choose File → Open, browse to the .wbk, and set the file-type dropdown to All Files so it appears. Open it, then Save As a normal .docx. If double-clicking does nothing, this dropdown trick is the fix.
Is it safe to delete?
Yes, if your main document is fine. The .wbk is only a spare copy. Delete it and you simply lose the extra backup — the working .docx is untouched.
FAQ
How do I open a .wbk file?
In Word, File → Open, set the type dropdown to All Files, pick the .wbk, then Save As a .docx.
Where does Word save .wbk backups?
In the same folder as the original document, named 'Backup of <name>.wbk'.
Can I delete a .wbk file?
Yes, as long as your main .docx is intact — it is only a backup copy.