A Quick Guide to DOIs and URLs

May 17, 2020
6 min read

Many referencing systems require a DOI or URL for online sources. But what exactly is the difference between DOIs and URLs? And how should you approach them as a proofreader?

What Are DOIs and URLs?

DOIs (digital object identifiers) and URLs (uniform resource locators) are both ways of linking to content online. So, what exactly is the difference between them?

DOIs are unique identifiers for published documents, such as academic journal articles. They are created, assigned, and standardized by the International DOI Foundation (IDF). You will usually find the DOI for an article on the host site or at the top of the first page.

DOIs are persistent and stable. As such, if an author includes the DOI for a source in a reference list, it will remain valid for all future readers (or at least for as long as the IDF exists).

You can also write DOIs either as a link or as metadata. For instance:

Link: https://doi.org/10.5694/mja18.00841

Metadata: 10.5694/mja18.00841

The correct way to write a DOI depends on the referencing system used.

A URL, meanwhile, is a standard web address. You will find it in the navigation bar of your browser (e.g., the URL for Knowadays is https://www.knowadays.com/). Some URLs, like DOIs, are permanent and stable: these are known as permalinks. However, others will change as websites are reorganized, rendering the old URL redundant.

Moreover, because the content or address of a web page may change, many style guides require a date of access alongside a URL. This is the date the author last accessed the website, just in case the address or information on the page later changes.

A Quick Guide to Different Style Guides

As with most things in proofreading, your approach to DOIs and URLs will depend on the style guide your client is using. However, most referencing systems favor DOIs when available.

In addition, most systems have rules for how to present DOIs and URL, including:

AMA Style

Use DOIs over URLs whenever possible.
Present DOIs as metadata, preceded by doi and a colon (e.g., doi:10.5694/mja18.00841).
If using a URL, include a date of access.

APA Style

Include a DOI for all sources that have one.
Use a URL if no DOI is available.
Present both DOIs and URLs as hyperlinks.

Chicago Style

Use DOIs over URLs where possible.
Present DOIs and URLs as links.
Shorten very long links if required.
If an online source has no date of publication or date that it was last modified, include a date of access in references.

MHRA Style

Provide a DOI or URL for all digital sources where possible.
If using a URL, provide a date of access.
Add DOIs and URLs inside angled brackets (e.g., <https://www.proofreadingacademy.com/>).
Present DOIs as metadata, preceded by doi and a colon (e.g., <doi:10.5694/mja18.00841>).

MLA Style

Use DOIs over URLs when possible.
Provide a date of access when using a URL.
Present DOIs as metadata, preceded by doi and a colon (e.g., doi:10.5694/mja18.00841).
Do not include “http://” or “https://” with URLs (e.g., www.proofreadingacademy.com).

When proofreading, you will want to ensure that your client has cited sources correctly according to the system they are using, which includes checking the use of DOIs and URLs.

If you do not have access to the relevant style guide, though, you can still check online for advice and make sure a consistent style is used.