Introduction to Solidity

Solidity is the language of smart contracts — programs that run on the Ethereum blockchain.

¶What is Solidity?

Solidity is a statically-typed language that compiles to bytecode for the Ethereum Virtual Machine (EVM).

Its contracts are immutable once deployed and handle real value, so correctness is everything.

¶Your first example

Here is Solidity saying hello. Read it top to bottom — every line earns its place.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract Hello {
    string public greeting = "Hello, world!";
}

Deploys a contract exposing a public `greeting` value.

¶Why learn Solidity?

• The dominant language for Ethereum and EVM chains.
• Smart contracts power DeFi, NFTs, and DAOs.
• A high-stakes domain where careful engineering pays.

¶Where it is used

• Smart contracts
• DeFi protocols
• NFTs
• On-chain applications

¶How this track works

Every topic here has four views, switchable with the tabs at the top of each page:

• Learn — the clear, practical walkthrough you are reading now.
• Deep — every detail: edge cases, the full API, and what is really happening.
• Reference — a scannable, no-fluff lookup for when you already know the shape.
• Cheatsheet — the one-page summary, printable, for quick recall.