Coming soon: Updated PubMed E-utilities!

Coming soon: Updated PubMed E-utilities!

Important Note: This release is being postponed and will go live Monday, November 21, 2022.

PubMed will be moving to an updated version of the E-utilities  API on November 15, 2022. As previously announced, this updated version of E-utilities will use the same technology as the web version of PubMed released in 2020. So, search results returned by the updated ESearch E-utility  will now match those of the website 

This update only affects E-utility calls with &db=pubmed. There are no changes to the E-utilities for other databases. You can refer to our previous post or watch our recorded webinar for more details on this update.  

Do I need to do anything to prepare?  

  • If you manage code that creates PubMed E-utility requests, review the changes below to ensure that your code will continue to function after the update. 
  • Up until launch, you can also verify your code on the public test server.

The test server is available through the following URL:

Test server:

To use the test server, replace the standard E-Utilities URL ( in your requests with the URL above. 

What will happen to the current version of the PubMed E-utilities after the release? 

The current E-utility URLs for PubMed (&db=pubmed) will continue to function after the E-utilities update is released, with only a few exceptions:  

  • ESearch will only be able to access the first 10,000 records retrieved by the search query (&retmax <= 10,000; &retstart + &retmax <= 10,000). 
  • EPost will only be able to accept up to 10,000 PMIDs in a single URL request. 
  • EFetch will no longer support returns in ASN.1 format. 

Will the output of PubMed E-utility calls be changing? 

Again, in almost all cases, no. Here are the exceptions: 

  • ESearch will now return exactly the same PubMed IDs (PMIDs) that are currently returned by web PubMed. 
  • EFetch will now return XML data by default (&retmode is not set) rather than ASN.1. In other words, the default value of &retmode will become “xml”.

 How can I keep in touch?  

Please write to us if you have any questions or concerns. 

You can also follow the NCBI Insights Blog and subscribe to the E-Utilities Announcement Mailing List for updates.  



4 thoughts on “Coming soon: Updated PubMed E-utilities!

    1. Yes, EDirect does have the workaround for the 10K limit. You currently need to run:

      export EDIRECT_PREVIEW=true
      This will be the case until the new API is the default for PubMed.

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