Zotero will scan the document and attempt to match all fields with your library.

However, if you are near the end of a project and just need to submit the file, this is a viable option.

Zotero uses absolute database paths and internal unique identifiers. Your laptop’s Zotero library contains the same items but with different internal keys (if you synced from scratch) or no keys at all (if you haven't synced).

If your document has been completely stripped of its metadata and exists only as plain text (e.g., "(Smith, 2023)"), you can use the RTF Scan feature. Save your document as an .rtf file. In the Zotero standalone app, go to Tools > RTF Scan. Select your document as the input file.

If you have the item open in your Zotero standalone app, you can simply drag and drop the item from the library into the citation search box!

In Google Docs, go to Zotero > Switch to Word. Download the file as a .docx, open it in Word, and click Refresh. Advanced Troubleshooting: The RTF Scan

Zotero is usually smart enough to realize the item was merged and will update the link automatically.