
Art.
Harvard Art Museums API is a free Art & Design API that requires apiKey authentication, is only available over HTTP and has unconfirmed CORS support.
API documentation for https://www.harvardartmuseums.org
Details from github.com.

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The Harvard Art Museums API is provided by harvardartmuseums (github.com). API documentation for https://www.harvardartmuseums.org
Yes. The Harvard Art Museums API is listed in the Art & Design 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.
Yes. The Harvard Art Museums API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the Harvard Art Museums API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
No. The Harvard Art Museums API is only available over plain HTTP, which browsers block on HTTPS sites. Call it from a server instead.