Navigation, geolocation and geographical data.
OpenStreetMap API is a free Geocoding API that requires OAuth authentication, is only available over HTTP and has unconfirmed CORS support.
Details from wiki.openstreetmap.org.

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Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
Brazilian postal codes (CEP) with IBGE coordinates, addresses and the companies registered there
The OpenStreetMap API is provided by OpenStreetMap Wiki (wiki.openstreetmap.org).
Yes. The OpenStreetMap API is listed in the Geocoding 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 OpenStreetMap API uses OAuth authentication, so you need to register for credentials before making requests.
CORS support for the OpenStreetMap API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
No. The OpenStreetMap API is only available over plain HTTP, which browsers block on HTTPS sites. Call it from a server instead.