DOI stands for “digital object identifier.” DOIs are alphanumeric character strings that serve to uniquely identify a resource (like an article or an e-book) and provide it with a permanent web address.

Here is an example of a DOI: https://doi.org/10.1016/S2352-3026(17)30123-0

In most scholarly journal articles, the DOI will usually be listed on the first page below the title or in the header or footer.

If you are unable to locate an article’s DOI, you can search the Crossref database to see if it has one. To do so, change the search to “Search metadata” and try a search for the article’s title. Note that not every article will have a DOI.

You can turn any DOI starting with 10 into a URL by adding https://doi.org/ before the DOI. For example, 10.1002/14651858.CD003766.pub6 can become https://doi.org/10.1002/14651858.CD003766.pub6. You may need to change old DOI formatting (doi:10.1016/S2352-3026(17)30123-0) to newer formatting (https://doi.org/10.1016/S2352-3026(17)30123-0) if you are working with an older article.

Consult the citation guide for the specific citation style that you are using to see how to integrate DOIs into your references. APA, MLA, and Chicago style require that you include DOIs in your references if sources have them.