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MLA Style Guide


URL stands for Uniform Resource Locator. A URL is nothing more than the address of a given unique resource on the Web. In theory, each valid URL points to a unique resource. Such resources can be an HTML page, a CSS document, an image, etc. In practice, there are some exceptions, the most common being a URL pointing to a resource that no longer exists or that has moved. As the resource represented by the URL and the URL itself are handled by the Web server, it is up to the owner of the web server to carefully manage that resource and its associated URL.

DOI stands for a Digital Object Identifier. A DOI is a persistent identifier or handle used to uniquely identify various objects, standardized by the International Organization for Standardization (ISO).  They are widely used to identify academic, professional, and government information, such as journal articles, research reports, data sets, and official publications. DOIs have also been used to identify other types of information resources, such as commercial videos. The DOI for a document remains fixed over the lifetime of the document, whereas its location and other metadata may change.

Which to use?

Referring to an online document by its DOI should provide a more stable link than directly using its URL. A DOI is preferable, but if a URL is the only location available, provide it instead.


  • You can usually omit http:// or https:// from URLs unless you want to hyperlink them and are working in a software program that does not allow hyperlinking without the protocol (but include https:// with DOIs). In professionally designed and typeset fixed-format works like print and PDF, the protocol can always be omitted.
  • Because web addresses are not static (i.e., they change often) and because documents sometimes appear in multiple places on the web (e.g., on multiple databases), MLA encourages the use of citing containers such as Youtube, JSTOR, Spotify, or Netflix in order to easily access and verify sources
  • Whether to link a URL, DOI, or permalink in a works-cited-list entry for a work published or submitted in digital format is optional. The MLA Handbook notes that one benefit of URLs is that they “may be clickable” in digital formats (48). The URLs in the e-book version of the handbook, for example, are linked.
  • The string “” is a way of presenting a DOI as a link, and “xxxxx” refers to the DOI number.
  • The preferred format of the DOI has changed over time. Although older works use previous formats (e.g., “http:/” or “doi:” or “DOI:” before the DOI number), in your reference list, standardize DOIs into the current preferred format for all entries. 
  • Copy and paste the DOI or URL from your web browser directly into your reference list to avoid transcription errors. Do not change the capitalization or punctuation of the DOI or URL.
  • Periods appear in a works-cited-list entry after the author, after the title, and at the end of each container string.