AdGuard DNS is a DNS service that blocks ads, trackers, malware and phishing sites at DNS level. You use it in place of your provider's resolver. There are three modes: default, family protection (which also blocks adult content and enforces safe search) and a non-filtering mode that only provides a secure connection. It supports DNSCrypt, DNS over HTTPS, DNS over TLS, DNS over QUIC and DNSSEC. You can manually block or allow domains per device. The public servers are free; paid personal servers offer more features. It is a hosted service with no self-hosting option.
The service is operated by AdGuard Software Limited, registered in Limassol, Cyprus, and is subject to EU law. The sources consulted name no foreign parent company. Organisations that want to run the resolver themselves can use the separate AdGuard Home, which the same developer offers as open source. For a European organisation, all DNS queries pass through AdGuard's infrastructure, and the product page does not describe log retention. It is worth checking this in advance in the privacy terms.