Constructing your identifiers

The persistent identifiers you register with us (DOIs) consist of a prefix and a suffix. We give you the prefix but you will need to come up with your own DOI suffix pattern. Some sample suffix patterns are available but feel free to come up with your own. Remember that a DOI should always be expressed as a URL, so it's best to keep your suffix short.

Your DOI suffix can be any alphanumeric string.  Limited punctuation is allowed, the approved character set for DOI suffixes is: "a-z", "A-Z", "0-9" and "-._;()/".  An expanded set of characters was supported prior to 2008, so you may see DOIs with now-banned characters (such as #, +, <, and >). DOIs created before the character set was restricted are still supported, but members are not able to create new DOIs with these characters. 

You don't need to include any specific or descriptive information in the DOI - that information is included in the metadata submitted when you register your content. If you do choose to include bibliographic information in a DOI string it will have no meaning within the Crossref or DOI system. Existing identifiers can also be used for the DOI suffix such as an ISBN, PII (personally identifying information), or existing internal numbering scheme.

When creating a DOI suffix:

• Be concise: Make the suffix easy to read. Remember, DOIs will appear online and in print; users will also re-type DOIs.
• Be unique: A suffix must be unique within a given prefix.
• Be case insensitive: A suffix is case insensitive, so 10.1006/abc is the same as 10.1006/ABC.
• Be consistent: The suffix should reflect a consistent, logical system that can be easily documented and readily understood by employees of your organization. For example, you might want the suffix to include existing internal identifiers (if they are concise).
• Avoid page numbers: It is possible to use traditional bibliographic metadata (such as journal, volume, and page) in constructing DOI suffixes because both this metadata and the DOI are persistent, but choosing a pattern that is tied to page numbers makes it difficult to put content online before pagination is complete for a print version, or if the items are published online only.
• Only use approved characters:  "a-z", "A-Z", "0-9" and "-._;()/"
• Use one or more nodes: You can use suffix nodes to reflect hierarchical information or levels of granularity. For example, the first node might be a multiple-letter code for the journal title, while successive nodes encode the year of article acceptance and the order of article acceptance. This is the scheme used by Academic Press, with resulting DOIs such as 10.1006/jmbi.1998.2354.
• Make suffixes extensible: DOI suffixes should be extensible. In the future, for instance, parts of articles, such as figures, graphs, and supplementary materials, might be assigned DOIs. Using the preceding Academic Press example, the second figure in the article might be assigned this DOI: 10.1006/jmbi.1998.2354.f002.  DOIs are case-insensitive: 10.5555/ABC123 is the same DOI as 10.5555/abc123 

Sample DOI suffix patterns