A digital object identifier (DOI) is a unique code which is routinely used to identify a piece of information such as a journal article or research report. It provides a stable link to the article, unlike a regular URL which may change if the page is moved.

As a result, if a DOI is present in the article you are citing, it is preferable to use this as the link in your reference list.

Where do I find the DOI?

If a DOI is available, you will usually find it somewhere near the journal article details - but it isn't a fixed point on the page and if you have downloaded a PDF, it can sometimes be in the page footer.

The DOI may look like a string of numbers:

Or it may contain a URL:

If you cannot find a DOI to use in your reference - don't worry. Not all articles have them. 

How do I use a DOI in my reference list?

If you are referencing an article as an electronic version, use our guide to referencing a journal article - if you can locate a DOI follow the section on articles with a DOI link, and if you can't locate the DOI use the section on articles without a DOI link. 

If the DOI is just a string of letters/numbers without a https:// prefix, you should put https://doi.org/ in front of the code to present it correctly.

If your journal article has page numbers, you are welcome to cite the article as a paper version instead. The paper version doesn't require a DOI or URL.