The APA 7th edition requires publication data for electronic sources. The DOI is the preferred electronic retrieval format because it provides a persistent link to a document’s location on the Internet. If no DOI is available, a URL can be included.
DOI is an abbreviation for digital object identifier. This is simply an ID number assigned to an ‘object’ such as a journal article (or a book). It allows the ‘object’ to be found across any physical location such as a database. Publishers assign it to online articles so that an article may be easily identified and found within the many possible databases in which they may reside.
As of March, 2017 the recommended format for the DOI within an APA reference is like this example: https://doi.org/10.1037/arc0000014