A DOI (Digital Object Identifier) is a unique combination of letters and numbers used to permanently identify an article or other work and provide a stable link to it online. Think of it as a permanent digital address for scholarly content.
DOIs identify with the content rather than a location. If the item changes location, the publisher is responsible for pointing the DOI to the new location.
DOI syntax has two parts: prefix and suffix. The prefix consists of two parts, the directory and registrant, and is assigned by a DOI registration agency. The suffix is assigned by the owner or publisher of the identified object. In order to use this syntax to implement resolution, the web address (https://doi.org/) must be placed before the prefix.
Source: Khedmatgozar, Hamid. (2020). Digital identifiers in scientific publishing and e-health. Medical Writing. 29. 74-78.
When you locate an article, the DOIs may be formatted as active or inactive.
An active DOI looks like a hyperlink.
An inactive DOI omits the https://doi.org/ and often starts with 10 (especially if assigned before 2011).
Simply add https://doi.org/ OR https://dx.doi.org/ before the DOI number to make it active.
Need to resolve a DOI that is in an inactive format?
Not all articles, or other information sources, have a DOI.
You can still cite an article without a DOI by includeing the article's URL, if available, or, if accessed through a database, cite it as your would a print article, omitting the DOI and database information.