## 4 State of Art about Data Availability in L2 Rollups
### On-Chain (Rollup Mode)  
The on-chain data posting, or rollup mode, is a basic functioning mode for data availability in rollup. To ensure the security, transparency, and verifiability of blockchain transactions, all related data must be publicly available on-chain to all network participants for verification. This approach leverages the security and consensus mechanisms of the L1 blockchain, ensuring data integrity and information accessibility. Compared to optimistic rollups, the zk-rollups do not require storing much data on-chain, as validity proofs can \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Rollup Name** & **Scalability** &
\begin{tabular}{c} **Security** \\ **Features** \\ \end{tabular} & **Strengths** & **Weaknesses** \\ \hline ZKSync [19] & High & Strong & Secure, Cost-effective & State Difference Only \\ \hline Starknet [20] & High & Strong & Scalable, Secure & State Difference Only \\ \hline Aztec (Private Blockchain) [21] & High & Strong & Privacy-preserving & Pending EIP-4844 Decision \\ \hline Scroll [22] & High & Strong & Scalable, Secure & Centralized Operator \\ \hline Linea [23] & High & Strong & Efficient, Scalable & Data Expiry After 18 Days \\ \hline DeGate V1 [24] & Medium & Strong & Trustless, Decentralized & Unclear Merkle Tree Storage \\ \hline Taiko [25] & High & Strong & Decentralized, Secure & Relies on Ethereum Validators \\ \hline Arbitum [26] & High & Strong & Low cost, high throughput & Dispute Delays \\ \hline Optimism [27] & High & Strong & EVM Equivalence & Dispute Delays \\ \hline Metis [28] & High & Strong & Cheapest Transactions & Less Community Adaptation and Data Withholding Attack \\ \hline Polygon (zkEVM) [29] & Medium to High & Strong & EVM Equivalence & Pending EIP-4844 Implementation \\ \hline Loopring (L2+Dex) [30] & Medium to High & Strong & Flexible, Secure & Centralized Operator \\ \hline Immutable X (NFT Solution) [31] & Medium to High & Strong & Decentralized, Flexible & Trust Issues in Validium Mode \\ \hline Manta Pacific [32] & High & Moderate & Scalable, Cost-effective & Relies on Celestia \\ \hline ZKFair [33] & High & Moderate & Scalable, Cost-effective & Relies on Celestia \\ \hline \hline \end{tabular}
\end{table} 
Table 4: L2 Rollup-based solutions to data availability: strengths and weaknesses. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Rollup Name** & **Data Availability Solution** & **Provider** & **Verification Mechanism** \\ \hline ZKSync [19] & On-chain (Calldata) & Ethereum & zk-SNAKKs \\ \hline Starknet [20] & On-chain (Calldata or Blob) & Ethereum & zk-STARKs \\ \hline Aztec (Private Blockchain) [21] & Off-chain (Initial Plan for Validium) & Off-chain & zk-SNAKKs \\ \hline Scroll [22] & On-chain (Calldata or blob) & Ethereum & zk-SNAKKs \\ \hline Linea [23] & On-chain (Blob) & Ethereum & zk-SNAKKs \\ \hline DeGate V1 [24] & On-chain (calldata) & Ethereum & zk-SNAKKs \\ \hline Taiko [25] & On-chain (calldata) & Ethereum & zk-SNAKKs \\ \hline Arbitum [26] & On-chain (blob) and off-chain (anytrust) & Ethereum/DAC & Fraud Proofs (Optimistic Rollup) \\ \hline Optimism [27] & On-chain (calldata or blob) & Ethereum & Fraud Proofs (Optimistic Rollup) \\ \hline Metis [28] & Off-chain & Memolabs & Hybrid (Fraud Proofs and Zk Proofs) \\ \hline Polygon (zkEVM) [29] & On-chain (Calldata) & Ethereum & zk-SNAKKs \\ \hline Loopring (L2+Dex) [30] & On-chain (calldata) & Ethereum & zk-SNAKKs \\ \hline Immutable X (NFT Solution) [31] & Onchain (calldata) or Off-chain & Ethereum/DAC & zk-STARKs \\ \hline Manta Pacific [32] & Off-chain (Celestia) & Celestia & zk-SNAKKs \\ \hline ZKFair [33] & Off-chain (Celestia) & Celestia & zk-SNAKKs \\ \hline \hline \end{tabular}
\end{table} 
Table 3: L2 Rollup-based solutions to data availability: technical characteristics. validate the authenticity of state transitions without revealing them. However, on-chain data availability still accounts for 80% of the total transaction cost [34].