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What is E-utilities?

Please note: following the release of the new version of PubMed, the results returned by E-utilities queries of PubMed may differ slightly from those returned in the web version of PubMed. A new PubMed API is currently under development: more information will be announced when available.

As new Insider's Guide classes are no longer being offered, this site is not currently being updated. Please refer to NCBI's E-utilities documentation for more up-to-date information.

If you’re reading this, you’ve probably used PubMed to search for citations to medical literature. PubMed ( allows you to search and retrieve bibliographic data, choose from several display formats, and share your results. You can use field tags that will limit your search to specific fields (for example: title, title and abstract, or MeSH terms). Behind the scenes, programs are processing your search terms and returning only the data that meet your search criteria.

When we talk about PubMed, we are referring to both the search interface and to the database itself - the largest collection of citations to medical journal literature in the world. PubMed is one of 38 databases built and maintained by the National Center for Biotechnology Information (NCBI) at NLM. Other NCBI databases include the NLM Catalog, MeSH, Gene, PMC (PubMed Central), and many more. Each of these databases has a layer of programming and a graphical user interface that makes it easy to enter your search terms and retrieve information.

E-utilities is simply another way to search PubMed and the other NCBI databases. E-utilities is an API, or Application Programming Interface: a set of rules, protocols, and tools for building software and applications. The E-utilities API allows you to search the NCBI databases through your own program. This means that you control exactly what fields you are searching, the specific data elements you retrieve, the format of the data, and how you share your results. When you use E-utilities to access PubMed, you are accessing the same data that you’d find at

Last Reviewed: July 30, 2021