E Utilities
The NCBI E-utilities API is free to use. Access tiers are differentiated by API key registration. All plans are no-cost; the API key raises the per-second rate limit and enables higher-volume access upon request.
E Utilities is the machine-readable pricing-plan profile for National Center for Biotechnology Information (NCBI) on the APIs.io network, conforming to the API Commons Plans specification.
It defines 2 plans, with named plans including Anonymous (No API Key), Registered API Key.
Tagged areas include Bioinformatics, Genomics, Life Sciences, PubMed, and Sequences.
Plans
Unauthenticated access to all nine E-utilities endpoints. Suitable for interactive queries and low-volume integrations. No registration required.
Free API key obtained from NCBI account settings. Raises the default rate limit to 10 requests per second. Higher limits are available upon request by emailing NCBI. Requires registering a tool name and contact email in request parameters.