World Data.
World Bank API is a free Science & Math API that requires no API key, is served over HTTPS and does not support CORS, so it should be called from a server.
Details from datahelpdesk.worldbank.org.

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The World Bank API is provided by World Bank Data Help Desk (datahelpdesk.worldbank.org).
Yes. The World Bank API is listed in the Science & Math category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
No. The World Bank API requires no authentication, so you can start making requests without signing up.
Not directly. The World Bank API does not allow CORS, so call it from a server, serverless function or proxy instead of front-end JavaScript.
Yes. The World Bank API is served over HTTPS, so it's safe to use in production.