Domain Info by LifeStep
DNS records, SPF/DMARC detection and TLS certificate expiry
Domain name search to find all domains containing particular words/phrases/etc.
DomainDb Info API is a free Development API that requires no API key, is served over HTTPS and has unconfirmed CORS support.

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.
DNS records, SPF/DMARC detection and TLS certificate expiry
Yes. The DomainDb Info 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 DomainDb Info API requires no authentication, so you can start making requests without signing up.
CORS support for the DomainDb Info API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The DomainDb Info API is served over HTTPS, so it's safe to use in production.