Marine species taxonomy, synonyms and distributions.
WoRMS 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 marinespecies.org.

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The WoRMS API is provided by World Register of Marine Species (marinespecies.org).
Yes. The WoRMS 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 WoRMS API requires no authentication, so you can start making requests without signing up.
Not directly. The WoRMS API does not allow CORS, so call it from a server, serverless function or proxy instead of front-end JavaScript.
Yes. The WoRMS API is served over HTTPS, so it's safe to use in production.