Resolve DNS names like it’s 2020

The Knot Resolver is a caching full resolver implementation, including both a resolver library and a daemon.



Knot Resolver 5.0.1 released

Wednesday, February 5, 2020


  • systemd: use correct cache location for garbage collector (#543)


  • cache: add cache.fssize() lua function to configure entire free disk space on dedicated cache partition (#524, !932)

Knot Resolver is trusted by companies worldwide

Why Knot?

Why not! Knot Resolver is a caching full resolver implementation written in C and LuaJIT, both a resolver library and a daemon. The core architecture is tiny and efficient, and provides a foundation and a state-machine like API for extensions. There are three modules built-in – iterator, validator, cache, and a few more are loaded by default. Most of the rich features are written in Lua(JIT) and C. Batteries are included, but optional.

Open source

Knot Re­solver is open-­source. It is com­plete­ly free to down­load and use. The source code is avail­able un­der GPL li­cense. Our de­vel­op­ment process is trans­par­ent and driv­en by the needs of com­mu­ni­ty and do­nat­ing user­s.


Mod­u­lar ar­chi­tec­ture of the li­brary keeps the core tiny and ef­fi­cien­t, and pro­vides a state-­ma­chine like API for ex­ten­sion­s. The Lua mod­ules, switch­able and share­able cache, and fast FFI bind­ings makes it great to tap in­to res­o­lu­tion pro­cess, or be used for your re­cur­sive DNS ser­vice. It's the Open­Resty of DNS.

High performance

The serv­er adopts a dif­fer­ent scal­ing strat­e­gy than the rest of the DNS re­cur­sors - no thread­ing, shared-noth­ing ar­chi­tec­ture (ex­cept MVCC cache that may be shared). You can start and stop ad­di­tion­al nodes de­pend­ing on the con­tention with­out down­time.

Secure and stable

The code is be­ing con­stant­ly checked by an ex­ten­sive test­ing suite to at­tain sta­bil­i­ty, as­sure in­ter­op­er­abil­i­ty with oth­er DNS im­ple­men­ta­tion­s, avoid per­for­mance re­gres­sion­s, and cir­cum­vent pos­si­ble se­cu­ri­ty-re­lat­ed prob­lem­s.

People said

What our customers love most about Knot Resolver

Knot Resolver has been a part of our infrastructure since 2017. We decided to use Knot Resolver because we already had a good experience with other CZ.NIC projects (BIRD, FRED, ...), and we are confident of their ability to solve problems quickly.

Milan Sýkora

Network Services Specialist, CETIN

Knot Resolver is the cornerstone of our public resolver service running on It provides the standard functionality we need and its modular architecture allowed us to develop additional features unique to our platform.

Ólafur Guðmundsson

Engineering director, Cloudflare

After evaluation of a variety of DNS resolvers, we found that Knot Resolver provides us with the best platform for building our unique threat prevention and DNS filtering solution.

Robert Šefr

CTO, Whalebone

Let’s talk

Feel free to contact our developers directly if you have any questions, sugesstions or comments. We will be happy to assist you.

Paid support

Knot Resolver is free software and is made available free of charge. Nevertheless, we highly recommend one of our paid support programs, starting at 5000 €/year.

One more thing

Knot Resolver is not the only child of the Knot family. Our other project Knot DNS is a high-performance authoritative-only DNS server which supports all key features of the modern domain name system.

Learn more