DOI display

Display guidelines for Crossref DOIs - effective March 2017

It’s really important for consistency and usability that all members follow these guidelines. We rarely have to change them and usually only do so for very good reasons. Please note that this is for display of Crossref DOIs, not anyone else’s DOIs, as not all DOIs are made equal.

The goals of the guidelines are:

  1. To make it as easy as possible for users to cut and paste or click on to share Crossref DOIs without technical knowledge (e.g. using right click to copy a URL).
  2. To get users to recognize a Crossref DOI as both a persistent link and a persistent identifier even if they don’t know what a DOI is.
  3. To enable points 1 and 2 above by having all Crossref members display DOIs in a consistent way.
  4. To enable robots and crawlers to recognize Crossref DOIs as URLs.

This page includes the following sections:

Crossref DOIs should always be displayed as a full URL link in the form

and should not be preceded by “doi:” or “DOI:”


Recent changes to guidelines

These new guidelines have a two important changes from the previous guidelines:

  • we have dropped the “dx” from the domain name portion of DOI links
  • we recommend you use the secure HTTPS rather than HTTP

NOTE: this change is backwards compatible and and will continue to work indefinitely.

Where to apply the display guidelines

Crossref DOIs should be displayed in the full URL form wherever bibliographic information about a piece of content is displayed.

An obligation of membership is that Crossref DOIs must be displayed on members’ response pages (also called landing pages). Crossref recommends that Crossref DOIs also be displayed or distributed in the following contexts:

  • Tables of contents
  • Abstracts
  • Full text HTML and PDF articles and other scholarly documents
  • Citation downloads to reference management systems
  • Metadata feeds to third parties
  • “How to Cite This” instructions on content pages
  • Social networking links
  • Anywhere users are directed to a permanent, stable, or persistent link to the content

Crossref members should not use proprietary, internal or other non-DOI URLs in citation downloads, metadata feeds to third parties or in instructions to researchers on how to cite a document.

Crossref DOIs in reference lists and bibliographies

Linking references in journal articles using Crossref DOIs is an obligation of membership and we strongly encourage you to link references in other content types. Because there are space constraints even in online references lists Crossref DOIs can be displayed in several ways, depending on the publisher’s preference and publication style. Crossref recommends the following options:

Option 1—Use the Crossref DOI URL as the permanent link


Soleimani N, Mohabati Mobarez A, Farhangi B. Cloning, expression and purification flagellar sheath adhesion of Helicobacter pylori in Escherichia coli host as a vaccination target. Clin Exp Vaccine Res. 2016 Jan;5(1):19-25.

Option 2—Display the text “Crossref” with a permanent DOI link behind the text


Galli, S.J., and M. Tsai. 2010. Mast cells in allergy and infection: versatile effector and regulatory cells in innate and adaptive immunity. Eur. J. Immunol. 40:1843–1851. Crossref


The International DOI Foundation created the ShortDOI service as an open system that creates shortcuts to DOIs, which can be long, and is similar to how URL shortening services work. For example, for the DOI the short form is Only one ShortDOI is created for each DOI and the ShortDOI returns exactly the same results as the DOI. For more information go to ShortDOIs are not widely used and we think it’s best to just create short DOIs in the first place. ShortDOIs are not DOIs themselves, which is confusing.

Frequently Asked Questions (FAQ)

Do we need to update how DOIs are displayed in already published content and existing PDFs?

No - you can make the change for new content going forward and do not need to update existing PDF files. You can update existing content if you want but this is optional. The current form for DOI links using will continue to work as long as Crossref and DOI System exist.

Can we make the display changes now or do we need to wait?

We have set the effective date for the new guidelines to be March 2017 to give people time to make changes but you can start using the new format right away if you like.

Some publishers have reported resistance from colleagues to the idea that when the DOI is displayed on the landing page - that is, the page the DOI links to - it should be a link. It should be because the DOI is both an identifier and a persistent link and it will be easier for users to always display the DOI as a full link so it can be copied easily. In addition, many users won’t know what a DOI is but they know what a link is and we want to encourage the DOI to be used as a persistent link and to be shared and use in other applications (e.g. reference managers) and have a fully linked DOI wherever a DOI appears enables this.

Do we need to redeposit our metadata to update the URLs?

No - there is no need to redeposit metadata. These guidelines cover how you display DOIs on your website.

Why not use “doi:” or “DOI:“?

When Crossref was founded in 2000 we recommended that DOIs be displayed in the format doi:10.NNNN/doisuffix and many publishers use “doi:[space][doinumber]” or “DOI: [space][doinumber]” or “DOI[space][doinumber]“. At the time that the DOI system was launched in the late 1990s it was thought that doi: would become native to browsers and automatically resolve DOIs. This never happened and it will never happen. Advantages to changing the display to a resolvable URL - even on the page the DOI itself resolves to - include the following:

  • A DOI is both a link and an identifier. Users will more easily recognize Crossref DOIs as an actionable link, regardless of whether they know about DOIs.
  • Users who do not know how to right-click on the link and choose “Copy Link”, will still be able to easily copy the DOI URL.
  • Programs (e.g. bots, etc.) will recognize the DOI as a link.

What about reference formats in style guides (APA, Chicago) that use “doi: [doinumber]“?

A number of style guides recommend that the DOI be included in the reference as an unlinked string. We will be contacting the main style guides to request that they update their recommendations for DOIs to use the full URL form.

Why not use “dx” as in

Originally the “dx” separated the DOI resolver from the International DOI Foundation (IDF) website but this changed a few years ago and the IDF recommends as the preferred form for the domain name in DOI URLs.

Why should we use HTTPS?

We take providing the central linking infrastructure for scholarly publishing seriously. Because we form the link between publisher sites all over the web, it’s important that we do our bit to enable secure browsing from start to finish. In addition, HTTPS is now a ranking signal for Google who gives sites using HTTPS a small ranking boost.

The process of enabling HTTPS on publisher sites will be a long one and, given the number of members we have, it may a while before everyone’s made the transition. But by using HTTPS we are future-proofing scholarly linking on the web.

Some years ago we started the process of making our new services available exclusively over HTTPS. The Crossref Metadata API is HTTPS enabled, and Crossmark and our Assets CDN use HTTPS exclusively. Last year we collaborated with Wikipedia to make all of their DOI links HTTPS. We hope that we’ll start to see more of the scholarly publishing industry doing the same.

Last Updated: 2017 January 27