Due to high demand for bioinformatics resources provided by the National Center for Biotechnology Information, some NCBI services have limited the number of requests per second (rps) to ensure smooth, unimpeded access for our user base worldwide. As of July 2021, dbGaP and Datasets services became subject to a default rate limitation of 3 rps for some of their public resources, much like those that currently apply to the Entrez Programming Utilities (E-utilities or EUtils). However, users may obtain a higher rps setting by utilizing API keys.

An API key is simply a unique alphanumeric string, which can allow you to access programmatic (non-Web-based) resources provided by the services above – and potentially other application programming interface (API)-based resources in the future – to request and retrieve data above the customary rate limitation of 3 rps. Users who register for an NCBI account can generate a unique API key through the settings page while logged into that account. The resulting key will then increase the user’s rate limit for these services to 10 rps. This 10 rps setting is then applied independently to each service; that is, users with a valid API key via NCBI account will be able to access EUtils at 10 rps (or more upon special request), and Datasets and dbGaP each at 10 rps as well.