# Introduction to zkSync for Developers
zkSync is a scaling and privacy engine for Ethereum. Its current functionality scope includes low gas transfers of ETH and ERC20 tokens in the Ethereum network. This document is a high-level description of the zkSync development ecosystem.
zkSync is built on ZK Rollup architecture. ZK Rollup is an L2 scaling solution in which all funds are held by a smart contract on the mainchain, while computation and storage are performed off-chain. For every Rollup block, a state transition zero-knowledge proof (SNARK) is generated and verified by the mainchain contract. This SNARK includes the proof of the validity of every single transaction in the Rollup block. Additionally, the public data update for every block is published over the mainchain network in the cheap calldata.
This architecture provides the following guarantees:
- The Rollup validator(s) can never corrupt the state or steal funds (unlike Sidechains).
- Users can always retrieve the funds from the Rollup even if validator(s) stop cooperating because the data is available (unlike Plasma).
- Thanks to validity proofs, neither users nor a single other trusted party needs to be online to monitor Rollup blocks in order to prevent fraud (unlike payment channels or Optimistic Rollups).
In other words, ZK Rollup strictly inherits the security guarantees of the underlying L1.
First of all, zkSync, as a scaling solution, is capable of making transfers, and doing them quick and cheap. Interfaces and principles of the core zkSync functionality are covered in the payments section of this documentation.
Secondly, zkSync is smart-contract friendly. Targeting 2021, it will be possible to either write contracts in Zinc, Rust-based type-safe programming language, or even reuse existing Solidity code. Contracts interoperability is covered in the contracts section.
Thirdly, zkSync is friendly for exchanges. Atomic swaps — an essential component of exchange protocols — are being actively developed (opens new window) and will soon go live. Stay tuned!
Finally, zkSync support is implemented for all the main platforms. Check out our SDK section of docs, and start developing with zkSync!