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.
1,000+ codders enrolled
53 lessons51 challenges209 quiz questions
- Beginner friendly
AI-assisted coding help
Hands-on interactive lessons
Audio narration on every lesson
Quizzes to test your knowledge
Free certificate of completion
Syllabus
Section 1
Fundamentals
Start sectionStartStart 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.Introduction
4 lessons324Variables and Types
6 lessons1125Arithmetic
5 lessons920Decisions
5 lessons920Functions
5 lessons920Contract State
5 lessons920Loops
5 lessons920Arrays
5 lessons920Data Models
5 lessons920Contract Rules
5 lessons720Final Challenges
3 lessons3
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January 2026
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Double or Nothing
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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.
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Promotion zoneEvery 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.
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.
Earn a Certificate
Earn certificates for every course you complete. Add them to your LinkedIn profile and resume to showcase your coding expertise to employers.
Certificate of CompletionPython Fundamentals
Add to LinkedInWhy 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,
uintandintsizes,boolandstring, arithmetic with integer division and remainders,if/elsechains, functions with parameters and return values,pureandview, state variables and public getters, constants,forandwhileloops, 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
uintcan't go negative, integer division that drops the remainder, when a function should bepure,view, or neither, and whatrequireactually 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?
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.
Do I get a certificate after the Solidity course?
Yes. Finishing the Solidity section gives you a free certificate of completion. A verifiable signal you can add to your resume or share on LinkedIn alongside any contracts, dApps, or audits you've worked on.
