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Unbound

A validating, recursive, caching DNS resolver.

Unbound is a validating, recursive, caching DNS resolver. It performs full recursion from the root servers downward, validates DNSSEC signatures, and caches answers locally — the kind of resolver that an ISP or a tech-conscious home user runs to avoid trusting whatever third-party recursive nameserver might otherwise be in front of them.

NLnet Labs has developed Unbound since 2007 along with the related authoritative server NSD. Both projects are funded by contracts with companies and infrastructure providers; the code itself is BSD-licensed.

Unbound is widely used as the local recursive resolver behind authoritative servers, on routers, and in Pi-hole-like setups where users want to combine ad blocking with self-hosted recursion. The default configuration has very secure defaults, which has made it a popular building block in privacy-focused home networking guides.

Debian/Ubuntu: sudo apt install unbound
Fedora/RHEL:   sudo dnf install unbound
Arch:          sudo pacman -S unbound
macOS:         brew install unbound