Quad9
Quad9 is a free, public Domain Name System (DNS) resolver service that focuses on security and privacy. It blocks access to malicious domains by using threat intelligence feeds from multiple cybersecurity partners, helping to protect users from phishing, malware, and botnet attacks. The service is operated by the Quad9 Foundation, a non-profit organization, and does not log user IP addresses to ensure privacy.
Developers should use Quad9 when they need a secure and privacy-focused DNS resolver for applications, networks, or personal use, especially in environments where blocking malicious traffic is critical, such as in corporate IT, IoT devices, or public Wi-Fi hotspots. It is particularly useful for enhancing security without requiring complex configurations, as it integrates easily with most systems and devices.