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Configure data availability

When you launch an Arbitrum chain, you set up data availability (DA) during the process. The choice affects how transaction data is stored and accessed for validation, thereby impacting security, costs, and performance.

Arbitrum Chains support multiple DA options, allowing you to choose based on your needs (e.g., maximum security vs. lower fees).

Available data availability options​

1. Rollup mode (Ethereum/Parent chain DA)​

This is the default option for chains that demand security. Transaction data is posted to the parent chain as calldata or blobs (after EIP-4844), using Ethereum's DA layer.

  • Config: Set arbitrum.DataAvailabilityCommittee to false in your chain config using the Chain SDK. No extra set up is needed.

2. AnyTrust mode​

This mode uses an external Data Availability Committee (DAC), which is a group of permissioned nodes that you choose and run, or outsource (RaaS). Instead of posting all the data to the parent chain, the sequencer sends a lightweight Data Availability Certificate (DACert) signed by a sufficient number of DAC members. The data is stored offchain and provided when needed.

  • Config: Set arbitrumDataAvailabilityCommittee to true in the chain config.
  • Deploy Data Availability Servers (DAS) for each DAC member (using Nitro's DAS software).
  • Generate a keyset (BLS public keys + quorum threshold) from DAC members.
  • Register the keyset on the SequencerInbox contract post-deployment.
  • Configure nodes (sequencer, batch poster, validators) to connect to DAS endpoints (via REST/RPC aggregators).

For a complete, detailed set of instructions on setting up DAC, DAS, and generating keysets refer to Get started.

3. Alternative data availability (Alt-DA)​

In this mode, data is posted to an external modular DA network, such as Celestia, using blobs and Data Availability Sampling. Integration happens through a sidecar server and onchain commmitments, such as Blobstream for verification.

  • Config: use a modified Nitro build that includes Celestia integration, such as the celestia-server sidecar. Set the DA provider in your node flags and adjust your preferences, for example, using Celestia as the main provider with a fallback to AnyTrust or Ethereum. Other DA options, such as EigenDA or Avail, can be added in a similar way.