Arbitrum Nova

Like Arbitrum One, Nova is an Optimistic Rollup. It assumes transactions are valid and only executes a fraud proof if a challenge is submitted. This provides the same strong security guarantees for execution, inheriting Ethereum's security for final settlement, while drastically reducing gas costs and increasing throughput compared to executing directly on the Ethereum Mainnet.

By moving the bulk of data storage off the expensive Ethereum calldata, Arbitrum Nova achieves transaction fees that are a fraction of a cent. This makes it economically viable for high-volume, low-value transactions, such as:

• Social media tipping and engagement rewards
• Blockchain gaming and in-game microtransactions
• High-frequency DeFi interactions for smaller users

Despite its off-chain data layer, Arbitrum Nova maintains a strong connection to Ethereum. State roots are periodically posted and settled on Ethereum L1, providing a secure checkpoint for finality. Assets can be trustlessly bridged to and from Ethereum L1, and the chain is EVM-compatible, allowing developers to deploy existing Solidity smart contracts with minimal changes.

Nova's architecture is specifically optimized for social and gaming applications where user experience depends on negligible transaction costs and high throughput. Projects like Reddit's Community Points (now on Polygon) initially explored this model, highlighting the need for a chain where community interactions aren't hindered by gas fees.

It's crucial to distinguish Nova from its sibling chain, Arbitrum One:

• Arbitrum One: Uses Ethereum for full data availability; higher security, slightly higher cost; for general DeFi and high-value apps.
• Arbitrum Nova: Uses the AnyTrust DAC for data availability; ultra-low cost; optimized for high-throughput social/gaming. They are separate chains with different trade-offs, both secured by Ethereum.

Arbitrum Nova uses a Data Availability Committee (DAC) to post transaction data off-chain, drastically reducing fees. This hybrid rollup model assumes at least one honest committee member, trading minimal trust assumptions for maximum cost efficiency compared to pure Optimistic Rollups.

Nova's ultra-low, predictable fees have made it a primary destination for blockchain gaming and social platforms. Key examples include:

• TreasureDAO: The decentralized gaming ecosystem and its MAGIC token.
• The Beacon: A popular social RPG.
• GMX: While known on Arbitrum One, its perpetuals trading also leverages Nova for specific integrations.
• Reddit Community Points: Initially piloted scaling for social tokens.

Assets move between Ethereum, Arbitrum One, and Nova via canonical bridges and third-party solutions.

• Arbitrum Bridge: The official bridge for moving ETH and tokens to/from Ethereum L1.
• Arbitrum's Native Token Bridge: For moving assets between Arbitrum One and Nova (L2 to L2).
• Third-Party Bridges: Protocols like Hop Protocol and Across provide fast, optimized transfers.

Developers on Nova use the same core tooling as the broader Arbitrum ecosystem, ensuring compatibility.

• EVM-Equivalence: Supports all standard Ethereum tools (Hardhat, Foundry).
• Arbitrum Nitro: The underlying stack that powers both Nova and Arbitrum One.
• RPC Providers: Services like Alchemy and Infura offer dedicated Nova endpoints.
• Block Explorers: Arbiscan provides full explorer functionality for the Nova chain.

Nova's fee structure is designed for high-throughput applications.

• Extremely Low Fees: Transaction costs are a fraction of a cent, funded in ETH.
• Fee Components: Costs cover L2 execution and the DAC's data posting service.
• Comparison: Fees are typically 5-10x lower than Arbitrum One, which itself is ~90% cheaper than Ethereum mainnet.

While not a primary governance chain like Arbitrum One (home to the Arbitrum DAO), Nova hosts DAOs for applications built on its chain. Governance for the Nova protocol itself, including DAC membership, is managed by the broader Arbitrum ecosystem governance.

The AnyTrust guarantee ensures that if the DAC fails to make data available, the system falls back to posting data directly to Ethereum L1, just like Arbitrum One. This provides a strong security floor, guaranteeing liveness and censorship resistance, but at the cost of higher fees during this fallback mode.

Like other Arbitrum chains, Nova uses multi-round interactive fraud proofs to resolve disputes. Validators can challenge invalid state transitions by forcing the execution of the disputed transaction on-chain. The security of these proofs depends on the availability of the transaction data, which is provided by the DAC.

Compared to a standard Optimistic Rollup (like Arbitrum One), Nova makes an explicit trade-off:

• Standard Rollup: Trustless security, with all data on L1.
• Nova (AnyTrust): Trusts the DAC to be honest and live, but offers ~10x lower fees. Security is conditional on at least 2 of N committee members being honest.

A single, permissioned sequencer operated by Offchain Labs orders transactions to provide instant confirmations. Users have censorship resistance through the force-include mechanism, allowing transactions to be submitted directly to L1 if the sequencer is unresponsive, ensuring the chain cannot be halted.

Nova is optimized for high-volume, low-value transactions where absolute decentralization is secondary to cost (e.g., gaming, social apps). The security model is considered suitable for applications where the financial value per transaction is low, making the trust assumption in the DAC an acceptable trade-off for ultra-low fees.