
Query information about your favorite Node.js libraries programatically.
npm Registry API is a free Development API that requires no API key, is served over HTTPS and has unconfirmed CORS support.
npm registry documentation.
Details from github.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.
API for calculating and comparing metrics of different websites using Page Rank algorithm
The npm Registry API is provided by npm (github.com). npm registry documentation.
Yes. The npm Registry API is listed in the Development 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 npm Registry API requires no authentication, so you can start making requests without signing up.
CORS support for the npm Registry API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The npm Registry API is served over HTTPS, so it's safe to use in production.