Addresses and domains for Quad9
IPv4 addresses
IPv6 addresses
Encryption
Auth-Name (DoT): Auth-Name (DoH): TLS-Port:Quad9 offers two additional DNS servers, whose addresses and domains are mentioned below.
For more information:
–– Service Addresses & Features | Quad9

About Quad9
An open DNS recursive service for free security and high privacy.
Quad9 blocks the query of malicious host names from a up-to-the-minute list of threats.
This blocking protects your computer, mobile device, or IoT systems from a variety of threats such as malware, phishing, spyware, and botnets, and can improve performance in addition to ensuring privacy. The Quad9 DNS service is operated by the Swiss-based Quad9 Foundation, whose goal is to create a safer and more stable Internet for all.
— Quad9 | A public and free DNS service for a better security and privacy

Use with apps
To use this DNS server in Stubby, add the following block to the configuration file. Instructions can be found here <- currently only availabel in German).
Use with apps
Quad9 offers the following applications. These applications make it unnecessary to change the settings in the device’s operating system.
Quad9 Connect App for Android
via Google Play / This app is still in the development phase. It may be unstable.
Properties above Quad9
Technologies:
- IPv4
- IPv6
DNS64is not supported by the provider- DNS-over-HTTPS (DoH)
- DNS-over-TLS (Dot)
- Applications for establishing a connection:
- Android
Characteristics:
- Automatically blocks maleware
- Free
- International
- Reliable
- Secure
Evaluation and reliability
DNSChoice.eu does not have the resources to provide a durable and reliable assessment of this DNS server. We refer here to DNSPerf.com from the Polish company PerfOps.
Operator
Under the control of: SWITCH c/o swissuniversities , Switzerland
Additional Quad9 DNS servers
Quad9 offers several different services for recursive DNS features. Each is represented by a different IP address (or in some cases, a host name) that you use to configure your systems.
Quad9 Secured w/ECS
Malware blocking, DNSSEC validation, ECS enabled
IPv4 addresses
IPv6 addresses
Encryption
Auth-Name: TLS-Port:Quad9 Unsecured
No malware blocking, no DNSSEC validation (recommended by the provider only for experts!)