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Learn Solidity

A free, interactive online Solidity course. You write and run a real smart contract on every lesson, with AI hints when your output doesn't match, and a free certificate when you finish the section.

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View syllabusSolidity playground

1,000+ codders enrolled

53 lessons51 challenges209 quiz questions

  • Beginner friendly
  • sparkles iconAI-assisted coding help
  • hint iconHands-on interactive lessons
  • volume On iconAudio narration on every lesson
  • quiz iconQuizzes to test your knowledge
  • certificate iconFree certificate of completion

Syllabus

1 sections53 lessons51 challenges209 quiz questions
  1. Section 1

    Fundamentals

    Start sectionStartExpandCollapse    Start with no programming experience and build a working foundation in Solidity: variables, decisions, functions, state, loops, arrays, mappings, structs, enums, guards and events. Practice every concept with exercises, mastery challenges and chapter quizzes.53 lessons87 challenges209 questions

    Introduction

    4 lessons324

    Variables and Types

    6 lessons1125

    Arithmetic

    5 lessons920

    Decisions

    5 lessons920

    Functions

    5 lessons920

    Contract State

    5 lessons920

    Loops

    5 lessons920

    Arrays

    5 lessons920

    Data Models

    5 lessons920

    Contract Rules

    5 lessons720

    Final Challenges

    3 lessons3
What you get
Everything you'll use to learn to code

Learn by Doing

Write real code, query databases, build websites, and master AI prompts. Our interactive lessons cover every skill modern developers need.

playground.js
Code Editor
1const greeting = "Hello, Coddy!"
2function sayHi(name) {
3    return greeting + " " + name
4}
5
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Input
"Alex"
Output
"Hello, Coddy! Alex"

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Take your coding journey on the go! No setup, no downloads - just open and start coding. Available on iOS, Android and Web with 4.9 star ratings.

Python
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Variables
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CONTINUE
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Journey
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Challenger League
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Every way to learn

Read, listen, test yourself, ask the AI, or look up anything you've already covered. Every lesson meets you where you are.

Intro to Variables
Audio

A variable is a named container that stores a value you can reference later in your program.

In Python, you create one by writing the name, an equals sign, then the value you want to store.

The value can change over time - reassigning the name simply points it to a new value.

1xSarah

Prove Your Skills

Earn certificates for every course you complete. Add them to your LinkedIn profile and resume to showcase your coding expertise to employers.

CoddyCertificate of Completion
This certifies thatJohn Doehas successfully completed
python iconPython Fundamentals
Verified
DateJan 2026
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Why learn Solidity with Coddy

  • Write and run real Solidity in your browser. No Remix, Hardhat, Foundry, MetaMask, or testnet - each lesson compiles your contract with solc and executes it on an EVM server-side, then shows the output, events, and any compiler errors instantly.
  • Solidity as smart contract developers actually use it: contract structure, uint and int sizes, bool and string, arithmetic with integer division and remainders, if/else chains, functions with parameters and return values, pure and view, state variables and public getters, constants, for and while loops, fixed and dynamic arrays in memory and storage, address, mapping, struct, enum, require, revert, events, and visibility.
  • AI hints walk you through the parts of Solidity that trip everyone up - memory vs. storage, why uint can't go negative, integer division that drops the remainder, when a function should be pure, view, or neither, and what require actually does to a transaction - so you build the right mental model of the EVM from lesson one.
  • Build real contracts, not just exercises - a profile card, a shared counter, an inventory tracker, a score board, and a reservation summary. Each project ships with tests that run against your compiled contract, so you see it behave end-to-end.

Frequently asked questions about learning Solidity

What is Solidity used for?

Solidity is the programming language for smart contracts on Ethereum and every EVM-compatible chain - Polygon, Arbitrum, Optimism, Base, BNB Chain, Avalanche and more. Contracts written in Solidity run tokens (ERC-20), NFTs (ERC-721), decentralized exchanges, lending protocols, DAOs, and games. If it moves value on an EVM chain, it was almost certainly written in Solidity.

Is Solidity hard to learn?

The syntax is close to JavaScript and C-family languages, so the basics come fast. What's different is the execution model: every function call costs gas, storage is expensive and permanent, integers have fixed sizes and no decimals, and a failed require undoes the whole transaction. The course teaches those ideas one lesson at a time, starting with variables and arithmetic and building up to mappings, structs, events, and guards.

Do I need to know JavaScript or blockchain before learning Solidity?

No. The course starts with no programming experience assumed - what a contract is, how to declare a variable, how to write a function. You don't need to understand consensus, gas markets, or wallets to write your first contract; those concepts are introduced where they matter, not before.

Do I need a wallet, testnet ETH, or Remix to take the course?

No. Every lesson compiles your Solidity with solc and runs it on an EVM on our servers, then shows the output and events. There is nothing to install and nothing to fund. When you're ready for real deployments, the same code works unchanged in Remix, Hardhat, or Foundry.

How long does it take to learn Solidity?

Solidity basics - types, arithmetic, decisions, functions, and state - take one to two weeks of daily practice. Getting comfortable with arrays, mappings, structs, events, and require guards, and finishing the section's projects, usually takes another two to four weeks. The step after that - testing frameworks, deployment, gas optimization, and security patterns like reentrancy guards - is its own learning curve on top of the language.

Can I learn Solidity online for free?

Yes. The interactive Solidity course is free - full lessons, coding exercises, mastery challenges, chapter quizzes, and a certificate. Contracts compile and run server-side, so you don't need any local toolchain to start writing real smart contracts.
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Learn Solidity with Coddy

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