OpenZeppelin

OpenZeppelin builds security tooling and reviewed smart contract infrastructure for Ethereum and other EVM chains. Its work spans the Contracts library of audited Solidity implementations for standards such as ERC-20 and ERC-721, the Upgrades plugins for proxy-based contract upgrades, Test Helpers for assertion-based contract testing, and Defender for secure operations including automated transactions, relayers and threat monitoring. The organisation also runs a smart contract auditing practice. Source code and documentation are published publicly, and the contract libraries are written primarily in Solidity.