GET esearch.fcgi
Operation ID: esearch
Auth: unknown
Description
ESearch searches and retrieves primary IDs (for use in EFetch, ELink, and ESummary) and term translations, and optionally retains results for future use in the user's environment.
Parameters (10)
(string, query, optional)
Web environment string returned from a previous ESearch, EPost or ELink call
(string, query, optional)
NCBI API key for higher rate limits
(string, query, required)
Database to search
Constraints: {'enum': ['pubmed', 'protein', 'nuccore', 'ipg', 'nucleotide', 'structure', 'genome', 'annotinfo', 'assembly', 'bioproject', 'biosample', 'blastdbinfo', 'books', 'cdd', 'clinvar', 'gap', 'gapplus', 'grasp', 'dbvar', 'gene', 'gds', 'geoprofiles', 'medgen', 'mesh', 'nlmcatalog', 'omim', 'orgtrack', 'pmc', 'proteinclusters', 'pcassay', 'protfam', 'pccompound', 'pcsubstance', 'seqannot', 'snp', 'sra', 'taxonomy', 'biocollections', 'gtr']}
(integer, query, optional)
Query key returned from a previous ESearch, EPost or ELink call
(integer, query, optional)
Total number of UIDs from the retrieved set to display (default: 20)
Constraints: {'maximum': 100000}
(string, query, optional)
Return mode. Use 'json' for JSON output, 'xml' for XML output.
Constraints: {'enum': ['xml', 'json']}
(integer, query, optional)
Sequential number of the first UID in the retrieved set to display (default: 0)
(string, query, optional)
Method for sorting results (varies by database)
(string, query, required)
Entrez text query
(string, query, optional)
When 'y', store results on the history server
Constraints: {'enum': ['y', 'n']}
Examples (3)
| Title | Type | URL | Action |
|---|---|---|---|
| Basic PubMed search for cancer research | curl |
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=pubmed&term=cancer+immunotherapy |
|
| Search with JSON output and pagination | curl |
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=nuccore&term=COVID-19+genome&retmode=json&retmax=10&retstart=0 |
|
| Search with history storage and sorting by relevance | curl |
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=pubmed&term=CRISPR+gene+editing&usehistory=y&sort=relevance&retmax=50 |
Probe History
Status Codes
| Time | Status | Latency | Size |
|---|---|---|---|
| 2026-03-23 10:48:03.620443 | 200 | 598ms | |
| 2026-03-23 09:03:46.184681 | 200 | 439ms | |
| 2026-03-23 09:01:42.001736 | 200 | 488ms |
Response Changes
| When | Old | New |
|---|---|---|
| 2026-03-23 09:03:46.184681 | f7b49873fac2 |
401e92aa6d88 |
| 2026-03-23 10:48:03.620443 | 401e92aa6d88 |
954846d6faa2 |