ZK-Rollups vs Validiums

Full data availability on-chain: All transaction data is posted to Ethereum L1 (as calldata or blobs). This provides Ethereum-level security for data, meaning the network can reconstruct state and recover funds even if the rollup sequencer fails. This is non-negotiable for high-value DeFi (e.g., Uniswap, Aave deployments) and institutional assets.

Paying for L1 data storage: Posting data to Ethereum incurs significant gas fees, creating a higher cost floor per transaction. While proofs are cheap, data is expensive. This makes micro-transactions (< $0.10) economically challenging. Examples: zkSync Era and StarkNet have higher per-tx costs than Validiums but lower than Ethereum mainnet.

Data availability off-chain: Only validity proofs are posted to L1; data is held by a separate committee or DAC (Data Availability Committee). This removes the L1 data cost bottleneck, enabling theoretical TPS in the 10,000s and ultra-low fees. Ideal for high-volume, low-value applications like gaming (Immutable zkEVM) and social feeds.

Security depends on data availability: Users must trust that the off-chain data committee(s) will not collude to withhold data. If data is lost, funds can be frozen. Solutions like EigenDA or Celestia aim to decentralize this, but it remains a different security model than pure rollups. Not suitable for uncollateralized, high-value settlements.

On-chain data availability: All transaction data is posted to Ethereum L1 (as calldata or blobs). This ensures users can always reconstruct state and exit, even if the rollup sequencer fails. This matters for high-value DeFi protocols (e.g., Aave, Uniswap V3) where capital preservation is non-negotiable.

Data posting fee overhead: Paying for L1 calldata/blobs increases cost per transaction, especially during network congestion. While cheaper than L1, it's more expensive than pure off-chain solutions. This matters for high-volume, low-value applications like microtransactions or gaming where fee sensitivity is critical.

Off-chain data availability: Only validity proofs are posted to L1, while data is handled by a committee or DAC. This eliminates L1 data fees, enabling >10,000 TPS and sub-cent transactions. This matters for mass-market dApps (e.g., Immutable X for NFTs, Sorare) requiring web2-scale UX.

Trusted data committee: Users rely on the off-chain Data Availability Committee (DAC) to provide data for exits. If the committee censors or fails, funds can be frozen. This matters for institutional custody or protocols where non-custodial guarantees are paramount, despite mitigations like fraud proofs on alternative layers.

Data availability on-chain: All transaction data is posted to Ethereum L1, enabling full chain reconstruction. This provides Ethereum-level security against censorship and data withholding attacks. This is critical for high-value DeFi protocols like Aave, Uniswap V3, and Lido that require maximum liveness guarantees.

Settles directly to L1: Assets and state proofs are finalized on Ethereum, enabling seamless trust-minimized bridging and composability with other L1 contracts. This matters for protocols building cross-layer systems (e.g., EigenLayer AVSs, Chainlink CCIP) that require strong settlement guarantees.

Pays for L1 calldata: Every transaction batch includes expensive data posting to Ethereum, leading to a higher fixed cost floor. While efficient, this can be prohibitive for high-throughput, low-value applications like gaming or microtransactions where Validium cost models are 10-100x cheaper.

Data availability off-chain: Only validity proofs are posted to L1, removing the main cost bottleneck. Enables 10,000+ TPS and sub-cent fees. Ideal for mass-adoption use cases like social apps (zkSync's ZK Porter), gaming (Immutable zkEVM), and high-frequency DEX aggregators.

Relies on Data Availability Committee (DAC): Requires a trusted set of operators to store and provide data. While proofs ensure correctness, liveness depends on the DAC. This adds operator risk and is less desirable for permissionless, credibly neutral applications that must avoid any trust assumptions.

Susceptible to data withholding attacks: If the DAC colludes or goes offline, users cannot generate proofs to withdraw assets. Solutions like zkPorter use cryptographic incentives, but this remains a theoretical liveness risk not present in pure ZK-Rollups. A key consideration for custody services and institutional funds.