
US federal rulemaking comments and dockets.
Regulations.gov API is a free Government API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Details from open.gsa.gov.

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.
Unofficial Philippine Professional Regulation Commission's examination schedule
Right-to-disconnect employment law by EU country: binding status, statute, and sanctions
District-level data for India: Census, NFHS-5, NCRB, RBI and more, reconciled onto one map
The Regulations.gov API is provided by GSA Open Technology (open.gsa.gov).
Yes. The Regulations.gov API is listed in the Government 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 Regulations.gov API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the Regulations.gov API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Regulations.gov API is served over HTTPS, so it's safe to use in production.