Overview

A universal app is a smart contract on ZetaChain that is natively connected to other blockchains like Ethereum, BNB and Bitcoin.

Unlike a regular contract, a universal app can accept contract calls, messages and token transfers from any connected chain. It can also trigger contract calls, and make token transfers on connected chains. These abilities enable universal apps to orchestrate complex multi-step transactions that span across chains.

For example, a Bitcoin user can interact with a universal app to send USDC to a recipient on Ethereum. An Ethereum user can buy an NFT on ZetaChain and send it to to their account on the BNB chain.

Universal apps are deployed on ZetaChain's universal EVM, which extends the EVM with omnichain interoperability features. This means your existing contracts will work out of the box on ZetaChain, and with some modifications, they can gain powerful omnichain capabilities.

Here's an example universal app:

pragma solidity 0.8.7;
 
import "@zetachain/protocol-contracts/contracts/zevm/interfaces/zContract.sol";
 
contract YourContract is zContract {
    function onCrossChainCall(
        zContext calldata context,
        address zrc20,
        uint256 amount,
        bytes calldata message
    ) external virtual override {
        // ...
    }
}

It’s implemented in Solidity and uses ZetaChain's universal EVM features (like onCrossChainCall) to handle calls from connected chains.

One of the key advantages of a universal app is that it requires deploying only a single contract on ZetaChain, eliminating the need for separate contracts on each connected chain. This reduces development time, lowers deployment costs, and minimizes the potential for errors. You can focus on creating robust, feature-rich applications without worrying about the complexities of managing multiple contracts across different blockchains.