Ethereum Chain Registry

Chain Resolver — Reference Hub

This app demos a unified resolver that maps a short label (like base) to an ERC-7930 chain identifier and back again via ENSIP-10

Looking for a deeper dive? Read the contracts README on GitHub.

Unified Resolver (ChainResolver.sol)

The unified resolver stores chain identifiers and label mappings (see 7930 chain identifier).

It implements ENSIP-10, meaning read operations use the extended resolver entrypoint resolve(bytes name, bytes data).

Mappings are keyed by labelhash, computed as labelhash = keccak256(bytes(label)) for the left‑most label (e.g., label = "optimism").

Enumerate registered chains via chainCount() and getChainAtIndex(uint256), which return each stored label and its associated chain name without relying on an off-chain index.

Forward and Reverse Resolution Flow
Forward Resolution

The ENS field text(..., "chain-id") (see ENSIP-5) returns the chain’s 7930 ID as a hex string. The data field data(..., "chain-id") (see ENSIP-24) returns the raw bytes. These values are written at registration by the contract owner (e.g., a multisig) and the resolver ignores user-set overrides. To resolve a chain ID:

  • DNS-encode the ENS name (e.g., optimism.cid.eth).
  • Compute labelhash = keccak256(bytes(label)) (e.g., label = "optimism").
  • Calls
    • resolve(name, encode(text(labelhash,"chain-id")))
    • resolve(name, encode(data(labelhash,"chain-id")))

You can also read the canonical human‑readable chain name for a label using the forward chain-name text key:

  • resolve(name, encode(text(labelhash, "chain-name"))) → returns the chain name (e.g., "Optimism").
Reverse Resolution

Reverse lookups use ENS text records. Build a key prefixed with"chain-name:" and suffixed with the 7930 hex (without a leading 0x), then call text(bytes32,string) via the Extended Resolver. This follows service key parameters per ENSIP‑TBD‑17. For example:

  • textKey (string): "chain-name:" + <7930-hex> (for example,"chain-name:00010001010a00")
  • Calls:
    • resolve(name, encode(text(labelhash, serviceKey)))
Repo: unruggable-labs/chain-resolver

7930 Chain Identifier

We use the chain identifier with a zero address from ERC-7930. It’s a compact blob that includes a chain type and a short reference.

  • EVM chains: the reference is the CAIP-2 eip155:<id> chain number, written as bytes. We treat that number as ≤ 32 bytes, so the total identifier is ≤ 40 bytes (8 bytes overhead + up to 32 for the ID).
  • Most non-EVM chains: their CAIP-2 references are also short in practice, so identifiers are typically ≤ 40 bytes too.
  • Full spec limit: the generic ERC-7930 format allows up to 263 bytes in total.

More details and examples: chain-resolver README

Deployments (Sepolia)

Canonical deployment addresses used across this app.

ChainResolver:0x88b3dd1797c94D5680863F122F84B61f4ff049A7

References

Standards that underpin the registry and resolvers.