A Digital Object Identifier (DOI) is a type of permanent identifier for digital objects (including articles, datasets, books or book chapters, and more).
They are used nearly universally by scientific journals, and are extremely common for scholarship within most other fields as well. Even some law reviews (including the Boston College Law Review!) have begun assigning DOIs to their articles.
The DOI Foundation has lots of interesting information on how DOIs are created and maintained, but all you need to know about them in the law review context is that they serve as a direct, permanent URL. Even if the website where the object was located moves (e.g. a publisher is acquired by another publisher), the DOI will point to the current location of the object.
This means that a DOI can serve as both the primary URL and the archival link in a citation, replacing the need to append a Perma link. The DOI can simply be appended to the end of the citation, e.g.:
Sara Womble, Comment, Two Steps Closer to Brady’s Abandoned Promise: The Fourth Circuit’s Cumulative Materiality Test for Brady and Napue Claims, 66 B.C. L. Rev. 2101 (2025), https://doi.org/10.70167/BYZW3426.
A DOI has three parts, as shown in the figure below (created by CrossRef):
The DOI resolver ("https://doi.org") will always be the same across all DOIs assigned by all organizations.
The DOI prefix (of the format "10.XXXX") is given to an organization by the DOI registry, is unique to the organization, and will be the same for all objects created by that organization.
The DOI suffix (usually a random string of letters and numbers) is assigned to an object by its creating organization, is unique to the object, and must be different from all other DOI suffixes created by that organization.
Note: together, the prefix and suffix may be referred to as the DOI identifier.
You can find the DOI in one of two places: on the object itself (e.g. on the first page of the PDF of an article), or on the official landing page that contains the object (e.g. the publisher's page where you can download or view an article).
You may see the DOI in one of several formats:
The full DOI (e.g. "https://doi.org/10.1000/182").
Just the identifier (e.g. "10.1000/182"), in which case you can create the URL by adding "https://doi.org/" to the front of the string (e.g. "https://doi.org/10.1000/182").
A Handle is another common type of permanent URL that work similar to a DOI, and can be cited the same way as a DOI. For example:.
Yoshio Tanaka, Yūyō Shokubutsu Zusetsu (1891), https://hdl.handle.net/2027/mdp.39015077802257.
Handles are common in digital archives such as HathiTrust.
The format of a Handle is: https://hdl.handle.net/XXXX/YYYY
You may also see the Handle shortened to just the ending string (e.g. "2027/hvd.hncbnw"), in which case you can create the URL by adding "https://hdl.handle.net/" to the front of the string (e.g. "https://hdl.handle.net/2027/hvd.hncbnw").
The Handle will be available on the same page as where you access the digital object (e.g. when viewing an item on HathiTrust, look on the sidebar under "Share").
Tip: most of the scanned books in Google Books are also available in HathiTrust. If you wish to provide a parallel citation to a scanned book that was found in Google Books, using the Handle URL supplied by HathiTrust allows you to easily provide a permanent URL to your readers.
