Introduction: ENS and Layer-2 Scaling
The Ethereum Name Service (ENS) transforms long hexadecimal wallet addresses into readable names like "alice.eth." As Ethereum transaction costs have risen, the need for efficient layer-2 scaling solutions has grown. Arbitrum, a leading optimistic rollup, now supports ENS, enabling users to resolve and manage .eth names with lower gas fees and faster confirmations. This article provides a neutral, technical overview of how ENS on Arbitrum functions, covering the underlying architecture, resolution process, registration mechanisms, and management tools.
Core Architecture of ENS on Arbitrum
ENS operates on Ethereum’s mainnet through a set of smart contracts that govern registration, renewal, and resolution. When ENS is used on Arbitrum, the core registry and resolver contracts are deployed on the Arbitrum network while maintaining compatibility with the mainnet ENS protocol. This integration exploits Arbitrum’s optimistic rollup design, which batches transactions off-chain and submits compressed data to Ethereum, drastically reducing gas costs. The ENS on Arbitrum implementation does not fork the protocol; instead, it mirrors ENS’s existing contracts, allowing names to be resolved both on layer-1 and layer-2. Developers and users interact with the same naming standards, but transactions on Arbitrum settle faster and at a fraction of the cost.
Key components include the ENS registry deployed on Arbitrum, which stores ownership and resolver pointers, and public resolvers that convert names to addresses. Arbitrum’s bridge ensures that data from layer-1 ENS contracts (like root .eth ownership) remains authoritative, while subdomain registrations and name updates occur within the layer-2 environment. This dual-layer design means that a user can register a subdomain or update records on Arbitrum without paying mainnet gas fees. For a detailed technical specification, the ENS GitHub record provides the exact contract addresses and deployment history for both mainnet and Arbitrum, serving as the definitive reference for developers auditing the architecture.
How Name Resolution Works on Arbitrum
Name resolution on Arbitrum follows the same general process as mainnet ENS: a user queries a name, the ENS registry retrieves the associated resolver address, and the resolver returns the Ethereum address or other records. However, there are key differences in how the resolution transaction is executed. On Arbitrum, resolution calls are processed entirely within the rollup, meaning they do not require a mainnet transaction. This enables dapps and wallets that support Arbitrum to resolve .eth names directly without incurring layer-1 fees, which can be particularly advantageous for frequent lookups in decentralized applications.
The resolution process relies on cross-chain communication for names that originate on mainnet. For example, if a user owns "example.eth" on mainnet and registers a subdomain "sub.example.eth" on Arbitrum, the resolver contract on Arbitrum is configured to check both local records and, via a bridge, mainnet records. Modern implementations often allow "fallback" resolvers that first check the local layer-2 registry and then query the mainnet ENS registry through Arbitrum’s message-passing infrastructure. This ensures that names remain globally unique. The result is that a .eth name registered on mainnet can be resolved on Arbitrum seamlessly, and names registered directly on Arbitrum can be resolved on other EVM chains if the resolver is properly configured.
For end users, the practical effect is faster resolution—typically within seconds—and minimal cost. Developers building on Arbitrum can integrate ENS resolution by calling the standard registry contract using tools like ethers.js or web3.js, with gas fees often less than $0.01 per lookup. This contrasts sharply with mainnet lookup costs, which can exceed $1 during peak congestion. The interoperability between layer-1 and layer-2 ENS also allows users to continue using the same .eth name across both environments, though they must ensure their records are updated on the layer where they intend to transact.
Registering and Renewing .eth Names on Arbitrum
Registering a new .eth name on Arbitrum follows a slightly different flow than on mainnet. On mainnet, registration requires committing to a name via a temporary commit-reveal mechanism, paying a fixed yearly fee, and waiting for expiry handling. On Arbitrum, similar contracts are deployed, but registration occurs entirely within the rollup. The process begins with checking name availability via a resolver or registry contract on Arbitrum. Users pay a reduced registration fee, typically denominated in ETH on the Arbitrum network, and the transaction is processed within seconds. Costs are substantially lower as Arbitrum L2 gas prices are a fraction of Ethereum’s.
Renewals also benefit from reduced costs. ENS names expire after one year on mainnet, but on Arbitrum, renewals can be executed with a single transaction that updates the expiry timestamp. Because the rollup submits aggregated data to Ethereum, the underlying name ownership data remains verifiable on the base layer. Users must be aware, however, that names registered solely on Arbitrum may not be immediately resolvable on mainnet unless they also maintain a record on the mainnet registry. For most practical use cases, names registered on Arbitrum will be accessible on Arbitrum-based dapps but may require an additional bridge transaction for mainnet resolution.
The registration process is streamlined for developers who want to deploy custom ENS names for their protocols. The ENS on Arbitrum implementation includes support for "wildcard" resolutions (ERC-634) and text records, allowing for rich name data. To manage ENS domains, users can connect their wallet to the ENS interface on Arbitrum, select a name, and update records like ETH addresses, avatars, or social links. This avoids the typical friction of mainnet gas costs, making frequent updates viable for both individuals and DAOs. It is worth noting that managing domains across multiple layers requires careful record-keeping: updating records on Arbitrum will not automatically update records on mainnet, and vice versa. Users should plan their naming strategy accordingly to avoid conflicting resolution data.
Use Cases, Tools, and Ecosystem Impact
ENS on Arbitrum has catalyzed several practical use cases. Decentralized exchanges (DEXs) hosted on Arbitrum can resolve ENS names for withdrawals and deposits, eliminating the need to copy-paste addresses. Gaming protocols on Arbitrum use ENS for player identity, allowing in-game assets to be linked to human-readable names. NFT marketplaces that have migrated to Arbitrum can display ENS-derived profiles, reducing friction for users who want to set avatar or profile links. In all these cases, the cost savings are significant: a single registerOrUpdate transaction on mainnet may cost $20–$50, whereas on Arbitrum it often costs under $0.10.
Several tools have emerged to support ENS on Arbitrum. The official ENS app now includes a toggle to switch between mainnet and supported layer-2 networks, including Arbitrum. Wallets like MetaMask and Rabby support ENS resolution on Arbitrum natively, enabling lookups directly from the interface. Developers can use the IPFS-resolver integration on Arbitrum for decentralized websites, resolving names to content that is hosted on IPFS and accessed through gateways. For those wanting to explore the codebase or contribute, the ENS GitHub record contains the complete deployment manifests and test scripts for Arbitrum, which developers can use to verify cross-chain behavior or implement custom resolvers.
The ecosystem impact is already measurable: as of early 2025, over 15,000 .eth names have been registered directly on Arbitrum, and millions of resolution transactions occur monthly on the rollup. This reduces load on the mainnet ENS registry while increasing ENS’s utility for users who primarily interact with layer-2 dapps. The optimistic rollup security model means that users retain the same level of trust assumptions as mainnet, with the addition of a fraud-proof period (typically seven days) during which transactions can be challenged. For most users, this trade-off is acceptable given the dramatic cost reduction.
However, there are limitations. Names registered on Arbitrum do not automatically appear on ENS mainnet; users must either register separately or use a bridging service that synchronizes records. Additionally, the ENS team recommends that users holding high-value names (e.g., premium short names) maintain primary registration on mainnet due to the higher security guarantees. For the vast majority of .eth users—who need reliable, cheap resolution for domain-linked wallets and profiles—ENS on Arbitrum offers a compelling alternative that preserves the core naming protocol while unlocking the operational advantages of rollup scaling.
Conclusion
ENS on Arbitrum delivers a practical, cost-effective extension of the Ethereum Name Service. By deploying core ENS contracts on an optimistic rollup, it enables fast, low-cost name resolution, registration, and management while maintaining compatibility with the mainnet protocol. Users can benefit from reduced transaction fees without sacrificing security, thanks to Arbitrum’s rollup design. The ability to resolve and manage .eth names on Arbitrum is becoming increasingly relevant as layer-2 ecosystems grow, and the available developer tools and wallet support ensure a smooth onboarding experience. As the ENS protocol continues to evolve, the layer-2 integration model—exemplified by Arbitrum—will likely serve as a template for future scaling efforts across other rollups and ecosystems.