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Chapter 6: DOIs and URLs

Academic writing almost always involves making reference to digital resources. Articles in scholarly journals are now always assigned DOIs, while discussions of contemporary artists or authors often involve quoting from interviews published only on websites, which must be referenced by URL. Academic writers therefore need to be able to cite DOIs and URLs, and this chapter describes how to write each in MHRA style. This is not a chapter on ‘how to reference digital resources’: for the most part, digital resources should be referenced very similarly to printed resources, as Chapter 7 on Referencing discusses.

§6.1. The Difference between a DOI and a URL

Both DOIs and URLs are ways to identify digital resources, but they work in different ways and cover different things. URLs are like addresses, saying on which web page something can be found. Because the web is constantly changing, with new websites appearing and disappearing, and existing websites going through internal rearrangements, URLs cannot be relied on to remain accurate over time. All that can really be said is that something was at a given page on a given date; it may or may not still be there today. As a result, URLs must always be cited with an access date: see below. Another issue with URLs is that the same content may be available from multiple locations. It is sometimes unclear what the best address for a resource is.

DOIs, by contrast, are permanent identification numbers for digital resources, in the same way that ISBNs provide permanent ID numbers for editions. Once allocated, these never change. It is customary now for each individual article, and even each short book review, in a scholarly journal to be allocated its own DOI. Many articles have been retrospectively allocated DOIs: Modern Language Review, for example, has DOIs going back to its foundation in 1905. DOIs are also sometimes given to specific entries in large online encyclopaedias. They are not confined to scholarly work or to commercial electronic publishing: governmental papers can also be given them (so, for example, many OECD, European Union, or HMSO publications have DOIs).

§6.2. How to Format a DOI

As is standard for abbreviations, the term ‘DOI’ is capitalized when discussing its role and use. In notation of an individual DOI, however, the letters are set in lower case followed by a colon (‘doi:’), followed immediately, and without a space, by the identifier itself, a series of alphanumeric codes broken up by slashes and colons. For example:

Frank A. J. L. James, ‘Faraday, Michael (1791–1867), Natural Philosopher, Scientific Adviser, and Sandemanian’, Dictionary of National Biography (Oxford University Press, entry dated 2004, rev. 2011), doi:10.1093/ref:odnb/9153

Els Jongeneel, ‘Art and Divine Order in the Divina Commedia’, Literature and Theology, 21 (2007), pp. 131–45, doi:10.1093/litthe/frm008

Do not give an access date, and do not write a DOI in angle brackets. Do not convert DOIs into URL form to produce a reference such as:

Els Jongeneel, ‘Art and Divine Order in the Divina Commedia’, Literature and Theology, 21 (2007), pp. 131–45 <> [accessed 11 May 2023]

§6.3. How to Format a URL

Web addresses should be written in angle brackets. Inside those brackets, URLs almost always begin ‘https://’; this is part of the URL and must be included. For example:

<> [accessed 17 November 2023]

An inconvenience of URLs is that addresses for individual pages inside large websites can be very long, and subject to change without notice as those websites go through periodic redesigns. Because of this, access dates must always be given when citing a URL: this is the date on which you, as the author, made use of the contents of the page. (Internet services such as the Wayback Machine sometimes allow pages dropped by their original hosts to be rediscovered, and an access date is invaluable in such cases.) It is good practice to recheck your URLs just before submitting a book or article to a publisher, to see if the material is still where you say it is: if so, you can then update the access date. If the page you are citing is of a kind where the published text is likely to change over time, it is important to check that the information or words you have cited remain the same. If not, retain your original access date.

Another good practice is to cite URLs in the shortest and friendliest form possible. The same page is often reachable by multiple URLs. If a website describes a URL as a ‘permalink’, this means it aspires to be a permanent location: blog engines such as WordPress often provide these. If available, use a permalink. For example:

<> [accessed 25 April 2023]

The ‘share’ option on a web page may provide a permalink. While shorter forms are generally preferable, avoid quoting URLs from services such as tinyurl or bitly which abbreviate other URLs: quote the originals.

Where the page to be cited is deep inside a website intended to be accessed by searching and not by URLs, it is sometimes appropriate to give just a page title and the URL for the site itself. For example, to refer to the entry ‘locator’ in the OED, format the note as follows:

See the entry ‘locator’ in Oxford English Dictionary, n.d., <> [accessed 25 April 2023]

The short form is more helpful to future scholars, since the OED website is likely to change its internal organization and URLs every few years.

When providing a URL for an entry in an online catalogue or database is unavoidable, there are ways in which it can be shortened. URLs often seem long because of the use of a ‘?’ and subsequent ‘&...’ details. For example:

<> [accessed 13 May 2023]

In almost all cases, those additional details are spurious as far as identification goes, since they are part of the website’s tracking data. (In this case, the film Alien has been accessed via a list of the top 250 movies in the Internet Movie Database.) The same page can be reached if everything from the question mark onwards is deleted:

<> [accessed 13 June 2023]

Similarly, a database may include your own search terms in the URL that is visible in its address bar. A search in the Internet Movie Database for Portrait of a Lady on Fire produces the URL:


This can be shortened to the core URL:


Though we strive to quote short URLs, they often still look lengthy on the page. When submitting a URL as part of word-processed copy, do not include line breaks or hyphenation, however ugly the result: leave it to the typesetter to deal with.

If a document such as a newspaper article is accessed through a database, via a library login, the search may produce what looks like a URL in the address line but is in fact a record of the search within the system, to which only fellow users of that library have access. Such internal locators typically contain the name of the database and a code for the library. In such cases, best practice is to locate the original source online and give its URL. If this is not possible, do not give a URL.

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