# Understanding zkSync: The difference between Validiums and Rollups

By [spacesmutje](https://paragraph.com/@spacesmutje) · 2024-06-04

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Validiums and zk-Rollups are both Layer 2 scaling solutions used on zkSync, but they differ significantly in their approach to data availability and security.

### Validiums

*   **Data Availability**: Validiums store data off-chain, which means that the transaction data is not published on the Ethereum mainnet (Layer 1). This off-chain data availability reduces the amount of data that needs to be stored on-chain, leading to lower gas costs and higher throughput.
    
*   **Security Model**: The security of Validiums relies on off-chain data availability managers. These managers are responsible for maintaining and providing access to the off-chain data. If these managers fail or act maliciously, users might be unable to access their funds because they cannot generate the necessary Merkle proofs.
    
*   **Use Cases**: Validiums are particularly suitable for applications that require high throughput and low costs, such as enterprise solutions that need auditability and privacy. They are also ideal for high-frequency trading and gaming applications where the trust assumptions are lower\[1\]\[2\]\[3\].
    

### zk-Rollups

*   **Data Availability**: zk-Rollups store transaction data on-chain. This means that all the data required to reconstruct the state of the rollup is published on the Ethereum mainnet. This on-chain data availability ensures that users can always access their funds, even if the rollup operator becomes unavailable or acts maliciously.
    
*   **Security Model**: zk-Rollups rely on cryptographic validity proofs (zero-knowledge proofs) to ensure the correctness of state transitions. This makes zk-Rollups more secure and trustless compared to Validiums, as the security is guaranteed by cryptographic methods rather than trust in off-chain data managers.
    
*   **Use Cases**: zk-Rollups are well-suited for applications that require high security and data availability, such as decentralized finance (DeFi) applications and other use cases where trust minimization is critical\[4\]\[5\]\[6\].
    

### Key Differences

*   **Data Storage**: Validiums store data off-chain, while zk-Rollups store data on-chain.
    
*   **Security**: Validiums depend on off-chain data availability managers, whereas zk-Rollups rely on cryptographic proofs for security.
    
*   **Throughput and Costs**: Validiums can achieve higher throughput and lower costs due to off-chain data storage, but at the expense of increased trust requirements. zk-Rollups have lower throughput and higher costs due to on-chain data storage but offer higher security and trustlessness\[1\]\[2\]\[3\]\[4\]\[5\]\[6\].
    

In summary, the choice between Validiums and zk-Rollups on zkSync depends on the specific requirements of the application, balancing the trade-offs between throughput, cost, security, and trust.

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Citations:

\[1\] [https://docs.zksync.io/zk-stack/concepts/validiums.html](https://docs.zksync.io/zk-stack/concepts/validiums.html)

\[2\] [https://www.defipulse.com/blog/rollups-validiums-and-volitions-learn-about-the-hottest-ethereum-scaling-solutions](https://www.defipulse.com/blog/rollups-validiums-and-volitions-learn-about-the-hottest-ethereum-scaling-solutions)

\[3\] [https://blog.matter-labs.io/introduction-to-hyperchains-fdb33414ead7](https://blog.matter-labs.io/introduction-to-hyperchains-fdb33414ead7)

\[4\] [https://chain.link/education-hub/zero-knowledge-rollup](https://chain.link/education-hub/zero-knowledge-rollup)

\[5\] [https://coinmarketcap.com/academy/glossary/zero-knowledge-rollups](https://coinmarketcap.com/academy/glossary/zero-knowledge-rollups)

\[6\] [https://docs.zksync.io/build/developer-reference/rollups.html](https://docs.zksync.io/build/developer-reference/rollups.html)

\[7\] [https://astar.network/blog/ethereum-layer-2-scaling-technologies-explained-39982](https://astar.network/blog/ethereum-layer-2-scaling-technologies-explained-39982)

\[8\] [https://docs.zksync.io/zk-stack/concepts/zk-chains.html](https://docs.zksync.io/zk-stack/concepts/zk-chains.html)

\[9\] [https://blog.matter-labs.io/zkrollup-vs-validium-starkex-5614e38bc263?gi=a27e57b00287](https://blog.matter-labs.io/zkrollup-vs-validium-starkex-5614e38bc263?gi=a27e57b00287)

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*Originally published on [spacesmutje](https://paragraph.com/@spacesmutje/understanding-zksync-the-difference-between-validiums-and-rollups)*