EUtilities Reference Guide
EUtilties API URL
EUtility API query URLs have three parts:
- Base URL
- EUtility endpoint
- One or more parameters
Figure 1. Parts of the Entrez API Query
Base URL
All EUtility queries start with this base url: https://eutils.ncbi.nlm.nih.gov/entrez/eutils/ .
Endpoints
The EUtilities API offers nine EUtility endpoints. In Table 1, see the list of EUtility endpoints with a brief description. For more information about each EUtility endpoint, in Table 1 click the endpoint in the first column to go to a page with detailed information.
Table 1: List of E-utilities in Order of Use
| EUtility Endpoint | Brief Description |
|---|---|
| ESearch | Returns a list of UIDs from a single database containing the searched text |
| ESummary | Downloads document summaries for each UID |
| EFetch | Returns a full data record |
| EGQuery | Searches for text in NCBI databases and returns the number of results for each database |
| ELink | Returns a list of UIDs for records that are linked between two databases. The UIDs returned by elink can be passed on directly to epost, esummary, or efetch. |
| EInfo | Retrieves information and statistics about a single database, including indexing fields and available link names. If no database is provided, EInfo returns the list of current databases in the network. |
| ESpell | Returns spelling suggestions for a text query |
| ECitMatch | Searches PubMed for citations |
| EPost | Saves a list of UIDs to use with other E-utilities like ESummary or EFetch |
EUtilities Parameters
Parameters are options you add to the base URL and EUtility to refine the results. Each EUtility has required and optional parameters. Null values or inappropriate parameters are generally ignored.
See Table 2 for a list of the most commonly used parameters. For a full list, see E-utilities Parameters for the required and optional parameter options for each EUtility.
| Parameter | EUtilities that Use it | What Does it Do? | Example |
|---|---|---|---|
| Database | EInfo ESearch ESummary EPost ELink ESpell ECitMatch EFetch |
Limits results to the provided database | db=pubmed |
| Term | EGQuery ESearch ELink ESpell |
Queries for the term you provide | term=asthma |
| UID | ESummary epost elink EFetch |
Limits results to the provided UIDs For more than one UID, add a comma to separate See UIDs for more information ADD LINK HERE |
id=19393038,30242208,29453458 |
| usehistory | esearch OTHERS |
Saves results to use with a subsequent EUtility query | usehistory=y |
| retmax | esearch esummary |
Total number of DocSums from the input set to be retrieved, up to a maximum of 10,000 | retmax=100 |
| retmode | esummary einfo esearch efetch elink |
Formats of the output | retmode=json retmode=xml |
| reldate | esearch | Sets the days to be searched relative to the current date, set reldate=1 for the most recent day | reldate=1 |
| mindate maxdate |
esearch elink |
Specifies the date according to the format YYYY/MM/DD, YYYY, or YYYY/MM A query must contain both mindate and maxdate parameters |
mindate=2000/01 maxdate=2022/12 |