What Is Solidity?

Solidity's syntax is influenced by languages such as JavaScript, C++ and Python. The developer writes the contract in Solidity; the compiler (solc) converts this code into bytecode that the EVM can run and into the ABI, which defines how to interact with the contract. The language includes constructs such as contracts, state variables, functions, events, modifiers and inheritance.

The vast majority of applications in the Ethereum ecosystem, such as ERC-20 tokens, NFT collections, decentralized exchanges and lending protocols, are written in Solidity. In a simple token contract, balances are kept in a mapping, and the transfer function decreases the sender's balance and increases the recipient's. Developers work with tools such as Remix, Hardhat and Foundry and with audited libraries such as OpenZeppelin.

Once deployed, smart contracts generally cannot be changed and directly manage money; therefore mistakes made in Solidity can lead to serious losses. Reentrancy attacks, access control errors and faulty arithmetic are among these risks; language updates, such as overflow checks becoming the default with version 0.8, have reduced some types of errors. On Ethereum, the Python-like Vyper language is also used as an alternative.