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What are Resolvers?

Resolvers are smart contracts that store and return information associated with ENS names. When you look up an ENS name, the ENS registry points to a resolver contract, which then provides the actual data (addresses, content hashes, text records, etc.). The resolver system is designed to be flexible and extensible through a profile-based architecture, where each profile implements specific functionality defined in various EIPs (Ethereum Improvement Proposals).

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PublicResolver

The PublicResolver is the most commonly used resolver implementation in ENS. It provides a general-purpose resolver suitable for most standard ENS use cases. The PublicResolver permits updates to ENS records by the owner of the corresponding name.

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Key Features

  • Multi-profile support: Implements multiple resolver profiles for different data types
  • Authorization system: Supports operators and delegates for managing records
  • Multicallable: Batch multiple operations in a single transaction
  • Versioning: Records are versioned to prevent stale data

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Authorization

The PublicResolver includes a sophisticated authorization system:
  • Operators: An address authorized for an owner may make any changes to names owned by that address
  • Delegates: A delegate authorized by an owner for a specific name may make changes to that name’s resolver records
  • Trusted controllers: Special addresses (ETH Registrar Controller, Reverse Registrar) that have elevated permissions
// Approve an operator for all your names
resolver.setApprovalForAll(operatorAddress, true);

// Approve a delegate for a specific name
resolver.approve(node, delegateAddress, true);

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Resolver Profiles

The PublicResolver implements the following profiles, each corresponding to specific EIPs:

ABIResolver

EIP-205: Store contract ABIs

AddrResolver

EIP-137, EIP-2304: Address resolution and multicoin support

ContentHashResolver

EIP-1577: IPFS and other content hashes

DNSResolver

DNS record support for ENS names

InterfaceResolver

EIP-165: Interface detection

NameResolver

EIP-181: Reverse resolution

PubkeyResolver

EIP-619: SECP256k1 public keys

TextResolver

EIP-634: Arbitrary text records

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Basic Usage

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Setting a Resolver

Before using a resolver, you must set it in the ENS registry: 
// Set the PublicResolver for your name
ens.setResolver(node, publicResolverAddress);

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Reading from a Resolver

// Get the resolver for a name
address resolverAddress = ens.resolver(node);
Resolver resolver = Resolver(resolverAddress);

// Read an address
address ethAddress = resolver.addr(node);

// Read a text record
string memory email = resolver.text(node, "email");

// Read a content hash
bytes memory hash = resolver.contenthash(node);

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Writing to a Resolver

// Must be called by the name owner, operator, or delegate
PublicResolver resolver = PublicResolver(resolverAddress);

// Set an Ethereum address
resolver.setAddr(node, myAddress);

// Set a text record
resolver.setText(node, "email", "[email protected]");

// Set a content hash
resolver.setContenthash(node, ipfsHash);

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ResolverBase

All resolver profiles inherit from ResolverBase, which provides:
  • Record versioning: Each node has a version number that increments when records are cleared
  • Authorization: Abstract isAuthorised() method that implementations must define
  • EIP-165 support: Interface detection capability
// Clear all records for a name (increments version)
resolver.clearRecords(node);
Clearing records increments the version number, effectively invalidating all previous records for that name without explicitly deleting them.

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Supported EIPs

The ENS resolver system implements the following Ethereum Improvement Proposals:
  • EIP-137: Ethereum Domain Name Service
  • EIP-165: Standard Interface Detection
  • EIP-181: Reverse ENS resolution
  • EIP-205: ENS support for contract ABIs
  • EIP-619: ENS support for SECP256k1 public keys
  • EIP-634: ENS support for text records
  • EIP-1577: ENS support for content hashes
  • EIP-2304: ENS support for multichain addresses

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Next Steps

PublicResolver

Learn about the PublicResolver contract in detail

Resolver Profiles

Explore each resolver profile and its functions

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