CNS Smart Contract

Crypto Name Service (CNS) is built on Ethereum and is effectively a bundle of Solidity smart contracts. Their source code is hosted in the dot-crypto repository and maintained by the Unstoppable Domains team. This page lists the smart contracts from that repository and gives a brief description of each along with links to the source code and deployment addresses. For high-level details about how CNS works, see CNS Architecture overview.

This page is divided into sections, grouping contracts by the following categories:


All contract addresses are available on the UNS GitHub repository

User-facing contracts

This section lists all the smart contracts that users can directly interact with.


Registry is the central smart contract, which stores all CNS domains. Implementing the ERC-721 non-fungible token standard, Registry defines domain ownership rules. It stores owner and Resolver addresses. For more details, see Architecture overview - Registry.

Source code: contracts/Registry.sol


Resolver is the smart contract that stores domain records and provides methods for domain resolution. For more details, see Architecture overview - Resolver.

Source code: contracts/Resolver.sol


ProxyReader provides an interface that allows users to fetch information about domains from both Registry and Resolver smart contracts in one call. For more details, see Architecture overview - ProxyReader.

Source code: contracts/ProxyReader.sol


SignatureController allows any account to submit management transactions on behalf of a token owner if an owner provides a signature for that call.

Source code: contracts/controllers/SignatureController.sol


DomainZoneController allows owners of a domain zone to mint subdomains. These subdomains can be managed only by the domain zone owners. For more details, see Architecture Overview - Alternative Ownership Models.

Source code: contracts/controllers/DomainZoneController.sol


TwitterValidationOperator is used when initiating Chainlink verification requests to link domain records with Twitter usernames.

Source code: contracts/operators/TwitterValidationOperator.sol

Registry controllers

The Unstoppable Domains team reserves the right to mint second-level domains and edit some Registry settings, such as token URI prefix. To avoid giving anyone absolute admin rights, Registry utilizes controllers that implement a limited set of admin actions.


The deployed version of the Registry smart contract only allows MintingController to mint second-level domains.

Source code: contracts/controllers/MintingController.sol


URIPrefixController enables the Unstoppable Domains team to edit the token URI prefix.

Source code: contracts/controllers/URIPrefixController.sol


The following interfaces can be used as guidelines for the minimal implementation of custom smart contract versions. Also, Solidity developers can rely on them for making calls to the official CNS smart contracts.


The IRegistry interface declares all the Registry events and methods (both read and write).

Source code: contracts/IRegistry.sol

Implemented by:


The IRegistryReader interface declares only read-only Registry methods.

Source code: contracts/IRegistryReader.sol

Implemented by:


The IResolver interface declares the minimal set of Resolver methods for configuring domain records.

Source code: contracts/IResolver.sol

Implemented by:


The IResolverReader interface declares the set of methods for reading Resolver records.

Source code: contracts/IResolverReader.sol

Implemented by:


The IDataReader interface declares the methods that are unique to the ProxyReader smart contract, which returns combined data from the Registry and Resolver contracts.

Source code: contracts/IDataReader.sol

Implemented by:


The IMintingController interface declares a set of methods for minting, which both MintingController implement.

Source code: contracts/controllers/IMintingController.sol

Implemented by:


The ISignatureController interface declares the functions that are implemented by SignatureController to enable Meta transactions for the Registry smart contract.

Source code: contracts/controllers/ISignatureController.sol

Implemented by:


The IURIPrefixController interface declares the functions that are implemented by URIPrefixController.

Source code: contracts/controllers/IURIPrefixController.sol

Implemented by:


The ERC677Receiver interface declares an ERC-677 method for receiving smart contracts.

Source code: contracts/util/ERC677Receiver.sol

Implemented by:

Utility contracts

Utility contracts are generally used to share common functionality between other smart contracts. This list also includes some contracts that are used internally by the Unstoppable Domains team.


The ControllerRole smart contract defines an Open Zeppelin Role, which is used by Registry to designate controllers.

Source code: contracts/util/ControllerRole.sol

Used by:


The MultiSend smart contract is used internally by the Unstoppable Domains team to fund worker accounts.

Source code: contracts/util/MultiSend.sol


SignatureUtil is a helper smart contract. Its implementation is used to extend smart contracts that require Meta Transactions.

Source code: contracts/util/SignatureUtil.sol

Used by:


The Truffle migrations smart contract.

Source code: contracts/Migrations.sol

Test smart contracts

There are several smart contracts that are used for testing purposes without being deployed to public networks or imported by other smart contracts.


The LinkTokenMock smart contract is used for testing TwitterValidationOperator.

Source code: contracts/test-helpers/LinkTokenMock.sol


RelayTest is used for testing relaying functionality for Meta Transactions.

Source code: contracts/test-helpers/RelayTest.sol


The Simple smart contract is used for testing ERC-721 receiver validation checks.

Source code: contracts/test-helpers/Simple.sol