
The Daily Journal of the United States Government.
Federal Register API is a free Government API that requires no API key, is served over HTTPS and has unconfirmed CORS support.
Search, browse and learn about the Federal Register. Federal Register 2.0 is the unofficial daily publication for rules, proposed rules, and notices of Federal agencies and organizations, as well as executive orders and other presidential documents.
Details from federalregister.gov.

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The Federal Register API is provided by Federal Register (federalregister.gov). Search, browse and learn about the Federal Register. Federal Register 2.0 is the unofficial daily publication for rules, proposed rules, and notices of Federal agencies and organizations, as well as executive orders and other presidential documents.
Yes. The Federal Register 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.
No. The Federal Register API requires no authentication, so you can start making requests without signing up.
CORS support for the Federal Register API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Federal Register API is served over HTTPS, so it's safe to use in production.