IACS class society, class status and survey dates for ships by IMO number.
Vessel Class Finder API is a free Transportation API that requires apiKey authentication, is served over HTTPS and supports CORS, so it can be called from the browser.
IACS publishes vessel-in-class data only as a ZIP/CSV download. Here is how to get class status, classification society and survey dates by IMO number from a REST API instead.
Details from vesselclassfinder.com.

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The Vessel Class Finder API is provided by Vessel Class Finder (vesselclassfinder.com). IACS publishes vessel-in-class data only as a ZIP/CSV download. Here is how to get class status, classification society and survey dates by IMO number from a REST API instead.
Yes. The Vessel Class Finder API is listed in the Transportation 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 Vessel Class Finder API uses apiKey authentication, so you need to register for credentials before making requests.
Yes. The Vessel Class Finder API supports CORS, so front-end JavaScript can call it directly.
Yes. The Vessel Class Finder API is served over HTTPS, so it's safe to use in production.