File Sharing and Storage.
ddownload API is a free Cloud Storage & File Sharing API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
ddownload.com - Fast and Free File Hosting. Make Money Uploading Files, No Files Deletion, Unlimited Bandwidth, Unlimited Storage, Unlimited File Size
Details from ddownload.com.

Unified API suite · now live
Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
Super simple file sharing, convenient, anonymous and secure
The ddownload API is provided by DDownload (ddownload.com). ddownload.com - Fast and Free File Hosting. Make Money Uploading Files, No Files Deletion, Unlimited Bandwidth, Unlimited Storage, Unlimited File Size
Yes. The ddownload API is listed in the Cloud Storage & File Sharing 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 ddownload API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the ddownload API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The ddownload API is served over HTTPS, so it's safe to use in production.