AbuseIPDB
IP/domain/URL reputation

IP/domain/URL reputation.
AlienVault Open Threat Exchange (OTX) API is a free Anti-Malware API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Learn about the latest cyber threats. Research, collaborate, and share threat intelligence in real time. Protect yourself and the community against today's emerging threats.
Details from otx.alienvault.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.
IP/domain/URL reputation
Provide malware datasets and threat intelligence feeds
Malware Archive / file sourcing
The AlienVault Open Threat Exchange (OTX) API is provided by LevelBlue Open Threat Exchange (otx.alienvault.com). Learn about the latest cyber threats. Research, collaborate, and share threat intelligence in real time. Protect yourself and the community against today's emerging threats.
Yes. The AlienVault Open Threat Exchange (OTX) API is listed in the Anti-Malware 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 AlienVault Open Threat Exchange (OTX) API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the AlienVault Open Threat Exchange (OTX) API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The AlienVault Open Threat Exchange (OTX) API is served over HTTPS, so it's safe to use in production.