The Digital Object Identifier (DOI) is a unique identifier used to provide a permanent link to digital objects. DOIs are now issued to most (new) journal articles.

Several professional association style guides now specify the use of the DOI when citing journal articles. For example, APA recommends the use of the DOI over the URL.

If you have a good reason to remove the DOI from the official style, it is possible to edit the CSL style. See this discussion for more details.