E-Utilities Quick Start Guide
E-Utilies Options:
- ESearch - Searches one database
- ESummary - Downloads summaries of database records
- Efetch - Returns full data records
- Elink - Returns data linked within the same database or between two databases
- EGQuery - Returns the number of records in each database for a search term
- EInfo - Returns statistics for a single database or a list of all NCBI databases
- ESpell - Returns spelling suggestions for terms within a single text query
- ECitMatch - Returns PubMed IDs (PMIDs) for a set of citation strings
- EPost - Saves your search history for use in another E-Utility
Base URL
All E-Utility queries begin with the following URL:
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/{ }.fcgi?
ESearch
To use Esearch:
- Start with the base URL: https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?
-
Add required parameters to the base URL
- If more than one parameter, join with an ampersand (&)
- Do not include spaces. Spaces may be replaced by '+' signs
| ESearch Required Parameters | Description | Example |
|---|---|---|
| db | Database you want to search | db=pubmed |
| term | Word or phrase you want to search for in the database | term=asthma |
3. Paste the URL with parameters into any internet browser and press Enter key
Result
Returns a list of UIDs displayed in the internet browser. By default, the maximum number of results is limited to 20.
- To change the number of results or add in other optional parameters, see FIX ME IM BROKEN ESearch Reference Guide for more information.
Example
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=pubmed&term=asthma
ESummary
To use ESummary:
- Start with the base URL: https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esummary.fcgi?
-
Add required parameters to the base URL
- If more than one parameter, join with an ampersand (&)
- Do not include spaces. Spaces may be replaced by '+' signs
| ESummary Required Parameters | Description | Example |
|---|---|---|
| db | Database you want to search | db=pubmed |
| id | One UID or a set of UIDs separated with commas that you want a document summary |
id=40654110 |
3. Paste the URL with parameters into any internet browser and press Enter key
Result
Returns document summaries (DocSums) that provide brief overviews of the records associated with the provided UIDs.
Example
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esummary.fcgi?db=pubmed&id=40654110
EFetch
To use EFetch:
- Start with the base URL: https://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?
- Add required parameters to the base URL
- If more than one parameter, join with an ampersand (&)
- Do not include spaces. Spaces may be replaced by '+' signs
| EFetch Required Parameters | Description | Example |
|---|---|---|
| db | Database you want to search | db=pubmed |
| id | One UID or a set of UIDs separated with commas that you want a document summary. There is no set maximum for the number of UIDs that can be passed to EFetch, but if more than about 200 UIDs are provided, the request should be made using the HTTP POST method LINK TO POST METHOD |
id=40654110 |
3. Paste the URL with parameters into any internet browser and press Enter key
Result
Returns full data records for the UIDs, in a format specified in the request, e.g., XML or FASTA.
Example
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=pubmed&id=19393038,30242208,29453458
ELink
To use ELink:
- Start with the base URL: https://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?
- Add required parameters to the base URL
- If more than one parameter, join with an ampersand (&)
- Do not include spaces. Spaces may be replaced by '+' signs
| eLink Required Parameters | Description | Example |
|---|---|---|
| db | Database you want to search | db=pubmed |
| id | One UID or a set of UIDs separated with commas that you want a document summary. There is no set maximum for the number of UIDs that can be passed to EFetch, but if more than about 200 UIDsare provided, the request should be made using the POST method LINK TO POST METHOD |
id=40654110 |
3. Paste the URL with parameters into any internet browser and press Enter key
Result
Returns a list of UIDs displayed in the internet browser. By default, the maximum number of results is limited to 20.
- To change the number of results or add in other optional parameters, see ELINK ADD LINK HERE for more information.
Example
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=pubmed&id=19393038,30242208,29453458
EGQuery
To use EGQuery:
- Start with the base URL: https://eutils.ncbi.nlm.nih.gov/entrez/eutils/egquery.fcgi?
- Add required parameters to the base URL
- If more than one parameter, join with an ampersand (&)
- Do not include spaces. Spaces may be replaced by '+' signs
| EGQuery Required Parameters | Description | Example |
|---|---|---|
| term | Word or phrase you want to search for | term=asthma |
3. Paste the URL with parameters into any internet browser and press Enter key
Result
Returns a list of UIDs displayed in the internet browser. By default, the maximum number of results is limited to 20. CHECK THIS : Instead of returning the actual records, EGQuery provides the number of matching records in each database, which is useful for quickly assessing the scope of your query across different NCBI databases.
- To change the number of results or add in other optional parameters, see EGQuery ADD LINK HERE for more information.
Example
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/egquery.fcgi?term=asthma
EInfo
To use EInfo:
- Start with the base URL: https://eutils.ncbi.nlm.nih.gov/entrez/eutils/einfo.fcgi?
- Add required parameters to the base URL
- If more than one parameter, join with an ampersand (&)
- Do not include spaces. Spaces may be replaced by '+' signs
- EInfo has no required parameters. The default database is PubMed
| EInfo Optional Parameters | Description | Example |
|---|---|---|
| db | Database you want to search | db=pubmed |
| version | Used to specify version 2.0 EInfo XML. The only supported value is ‘2.0’. |
version=2.0 |
| retmode | Determines the format of the returned output. The default value is ‘xml’. Also ‘json’ is supported. |
retmode= son |
3. Paste the URL with parameters into any internet browser and press Enter key
Result
EInfo provides one of the following:
- When a database parameter is given, statistics for a single database including lists of indexed fields and link names returns
- When no database parameter is given, a list of the names of all valid databases returns
Examples
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/einfo.fcgi?db=protein
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/einfo.fcgi?db=protein&version=2.0&retmode=json
ESpell
To use ESpell:
- Start with the base URL: https://eutils.ncbi.nlm.nih.gov/entrez/eutils/espell.fcgi?
- Add required parameters to the base URL
- If more than one parameter, join with an ampersand (&)
- Do not include spaces. Spaces may be replaced by '+' signs.
| ESpell Required Parameters | Description | Example |
|---|---|---|
| db | Database you want to search | db=pubmed |
| term | Word or phrase you want to search for in the database. Spaces may be replaced by '+' signs. |
term=asthma |
3. Paste the URL with parameters into any internet browser and press Enter key
Result
Provides spelling suggestions for terms within a single text query
Example
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/espell.fcgi?db=pubmed&term=asthmaa+OR+alergies
ECitMatch
To use ECitMatch:
- Start with the base URL: https://eutils.ncbi.nlm.nih.gov/entrez/eutils/ecitmatch.fcgi?
- Add required parameters to the base URL
- If more than one parameter, join with an ampersand (&)
- Do not include spaces. Spaces may be replaced by '+' signs
| EINfo Required Parameters | Description | Example |
|---|---|---|
| db | Database you want to search | db=pubmed |
| bdata | Citation strings | Each input citation must be represented by a citation string in the following format: |
| journal_title | year | volume |
| retmode | format | Determines the format of the returned output. The default value is ‘xml’. Also ‘json’ is supported. |
3. Paste the URL with parameters into any internet browser and press Enter key
Result
- Retrieves PubMed IDs (PMIDs) that correspond to a set of input citation strings.
Examples
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/einfo.fcgi?db=protein
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/einfo.fcgi?db=protein&version=2.0&retmode=json
EPost
To use EPost:
- Start with the base URL: https://eutils.ncbi.nlm.nih.gov/entrez/eutils/epost.fcgi?
-
Add required parameters to the base URL
- If more than one parameter, join with an ampersand (&)
- Do not include spaces. Spaces may be replaced by '+' signs
| ESummary Required Parameters | Description | Example |
|---|---|---|
| db | Database you want to search | db=pubmed |
| id | One UID or a set of UIDs separated with commas. All must be from same database |
id=40654110 |
3. Paste the URL with parameters into any internet browser and press Enter key
Result
EPost does the following:
- Uploads a list of UIDs to the History server
- Appends the list of UIDs to an existing set of UIDs attached to a Web Environment or creates a new Web Environment if one does not yet exist.
Examples
Post UIDs to History Server:
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/epost.fcgi?db=pubmed&id=11237011,12466850
Attach UIDs to Web Environment: