Unbound is a validating, recursive, caching resolver. It is designed to be a fast and lean set of modular components that incorporate modern features, such as DNSSEC validation, IPv6 support and a client resolver API as an integral part of the architecture.

Unbound runs on FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows, with packages available for most platforms. Unbound is included in the base-system of FreeBSD and OpenBSD. The software is distributed free of charge in open source form under the BSD license.

Installation and configuration of Unbound is designed to be easy. Setting up a validating, recursive, caching resolver which can be used for a single machine or multi-machine LAN can be done with only a few lines of configuration. Unbound supports modern standards such as DNS over TLS to prevent DNS spoofing and ensure DNS privacy.