The Ethernaut

WTF Solidity is a free open-source Solidity course running from basics to advanced topics, with runnable code examples in Chinese and English. Beginners work through it to learn Solidity by editing and running each example.

Building Secure Contracts is Trail of Bits' collection of guidelines, checklists, and training material for writing and reviewing Solidity contracts. Solidity developers work through its exercises and program analysis tutorials while building and reviewing code.

Damn Vulnerable DeFi is a hands-on Ethereum security training environment featuring realistic Solidity and DeFi exploitation challenges.