If the DOI isn’t on the article, look it up on the website CrossRef.org (use the “Search Metadata” option).
To find the current web page associated with a DOI, go to the DOI Resolver page at DOI.org.
A DOI, or Digital Object Identifier, is a string of numbers, letters and symbols used to permanently identify an article or document and link to it on the web.
A DOI will help your reader easily locate a document from your citation. Think of it like a Social Security number for the article you’re citing — it will always refer to that article, and only that one.
APA 7th Edition requires that you have a DOI for all items if one exists, no matter if the item is print or online.