What is Arbitrum Nova and how is it different from Arbitrum One?

Arbitrum Nova is an Ethereum scaling chain built by Offchain Labs for low-cost transactions. It uses the same Nitro software as Arbitrum One, but instead of posting all transaction data to Ethereum, it relies on a small group of known parties to store it. The broader Arbitrum network and its ARB token are covered in what is Arbitrum.

What is Arbitrum Nova vs Arbitrum One?

Arbitrum's docs describe the split simply. Arbitrum One is a rollup that posts its transaction data to Ethereum and adds no trust assumptions beyond Ethereum's own. Nova uses AnyTrust, a variant of Nitro, which keeps data offchain in the normal case to lower fees.

So the difference is not speed or apps but where the data lives. On Arbitrum One, anyone can rebuild the chain's state from data on Ethereum. On Nova, that ability depends on a committee being willing to hand the data over, which is why Nova is usually not counted as a full rollup. For why that matters, see what is data availability.

What is the Arbitrum Nova data availability committee?

The Data Availability Committee, or DAC, is a set of members who each store copies of Nova's transaction batches. The Inside AnyTrust docs explain the flow. The sequencer sends each batch to every member, members sign it, and once enough signatures arrive the sequencer posts a short certificate to Ethereum instead of the full data.

The design assumes at least two members are honest. With that assumption, the docs say a valid certificate needs signatures from all but one member. The committee cannot forge transactions or move funds, but if it withheld data the chain could stall. If too few members respond, the sequencer falls back to rollup mode and posts full data to Ethereum.

At launch in August 2022, Offchain Labs named seven members: Offchain Labs, Google Cloud, Reddit, FTX, Consensys, P2P and QuickNode. Membership has changed since. A November 2023 Security Council action removed Reddit and set the committee at five of six, according to the Arbitrum forum. The current list can change again, so check Arbitrum's governance channels for the latest.

What is Arbitrum Nova used for?

Offchain Labs pitched Nova at web3 gaming and social apps, where users make many small transactions and low fees matter more than the strongest possible security. Its best-known early user was Reddit, which moved its Community Points tokens to Nova in 2022. TechCrunch reported in October 2023 that Reddit was phasing the program out, citing cost and the regulatory climate.

Arbitrum's docs frame the choice this way. Apps that need full trustlessness fit Arbitrum One, while apps that need higher throughput at lower cost may accept Nova's extra assumption. For teams that launch their own AnyTrust chains, see what is an appchain.