Free interactive courses
Learn to code with free interactive courses
Pick a programming language and start writing real code in your browser. Hands-on lessons, AI-assisted hints, and a free certificate at the end.
Browse all programming languages
Pick a language to start a free, interactive course. Each one has hands-on lessons, AI hints, and a free certificate when you finish.
HTMLLearn HTML free with interactive lessons, real coding exercises, AI hints, and a certificate. HTML basics, tags, forms - runs in your browser, no install.JavaScriptLearn JavaScript free with interactive lessons, AI hints, and a certificate. JS basics, ES6, DOM and projects - runs in your browser, no install required.PythonLearn Python free with interactive lessons, AI hints, and a certificate. Start with Python basics, build real projects, no install - runs in your browser.C++Learn C++ Free with interactive lessons, AI hints, and a certificate. C++ basics, real projects - runs in your browser.CLearn C programming free with interactive lessons, AI hints, and a certificate. C basics, pointers, memory - runs in your browser, no install.SQLLearn SQL Free with interactive lessons, AI hints, and a certificate. SQL basics, real projects - runs in your browser.C#Learn C# online with interactive lessons, real exercises, AI hints, and a free certificate. C# basics, OOP, classes - runs in your browser, no install.JavaLearn Java free with interactive lessons, real coding exercises, AI hints, and a certificate. Syntax, OOP, projects - in your browser, no install.GOLearn Go programming free with interactive lessons, AI hints, and a certificate. Go basics, goroutines, channels - runs in your browser, no install.PHPLearn PHP online with interactive lessons, real exercises, AI hints, and a free certificate. PHP basics, web dev, projects - runs in your browser.RLearn R programming free with interactive lessons, real R exercises, AI hints, and a certificate. R basics, data analysis - no install, runs in browser.DartLearn Dart programming free with interactive lessons, AI hints, and a certificate. Dart basics, async, OOP - runs in your browser, no install required.RustLearn Rust programming free with interactive lessons, AI hints, and a certificate. Rust basics, ownership, borrowing - in your browser, no install.LuaLearn Lua programming free with interactive lessons, AI hints, and a certificate. Lua basics, scripting, Roblox-ready - runs in your browser, no install.GDScriptLearn GDScript free with interactive lessons, AI hints and a certificate. Variables, loops, arrays, dictionaries, classes and signals, run on a real Godot engine in your browser.UnityLearn Unity scripting in C# free. Write MonoBehaviour scripts with physics, UI and scenes, then play your 3D games in the browser. Nothing to install.Machine LearningLearn machine learning with real Python: NumPy, pandas, matplotlib and scikit-learn. Every lesson has a chart, and your own charts appear as you code. Free.RubyLearn Ruby programming free with interactive lessons, AI hints, and a certificate. Ruby basics, blocks, OOP - runs in your browser, no install.SwiftLearn Swift programming free with interactive lessons, AI hints, and a certificate. Swift basics, optionals, classes - runs in your browser, no install.VerilogLearn Verilog free with interactive lessons, AI hints, and a certificate. HDL basics, modules, always blocks, FSMs - simulate in your browser, no install.ArduinoLearn Arduino programming free, from zero. Write C++ sketches for LEDs, buttons, servos and sensors and run them on a board in your browser. No kit needed.FlutterLearn Flutter app development free, from zero. Write Dart, press Run and your app opens on a phone screen next to your code. No Android Studio needed.GodotLearn Godot game development free, from zero. Write GDScript, press Play and your game runs in the real Godot engine beside your code. Nothing to install.DjangoLearn Django free with a hands-on tutorial. Build six Python web projects in real Django that runs in your browser beside the code. Nothing to install.PygameLearn pygame free, from zero. Write Python, press Play and your game runs beside your code on the real pygame-ce. Seven sections, nothing to install.Node.jsLearn Node.js free: write JavaScript for the server and build six projects, from a command-line tool to Express and NestJS APIs, in your browser.SolidityLearn Solidity free with interactive lessons, AI hints, and a certificate. Contracts, state, mappings, structs, events, require - compiled and run on an EVM in your browser, no wallet or setup.KotlinLearn Kotlin free with an interactive, beginner-friendly course: null safety, when, loops, functions, lists. Run Kotlin in your browser, get AI hints, earn a certificate.AssemblyLearn Assembly free with interactive lessons, AI hints, and a certificate. x86-64 NASM basics, registers, memory, syscalls - assemble and run in your browser, no install.ReactLearn React free with interactive lessons, real JSX challenges and AI hints. Components, props, state, hooks, then Next.js - all in your browser, certificate included.AI PromptsLearn prompt engineering free with interactive lessons, real prompt examples, and a certificate. AI prompts for ChatGPT, Claude, and LLMs in your browser.TerminalLearn Linux free, from your first command to bash scripts, in a real terminal that runs in your browser. Interactive lessons for beginners, AI hints, and a free certificate.ExcelLearn Excel free with hands-on lessons in a real spreadsheet. Formulas, VLOOKUP, IF, pivot tables - runs in your browser, no install, free certificate.TypeScriptLearn TypeScript free with interactive lessons, AI hints and a certificate: types, interfaces and generics, in your browser.GitLearn Git and version control free with interactive lessons, real repo exercises, and a certificate. Commits, branches, merging, conflicts - in your browser.DockerLearn Docker free with hands-on lessons and a certificate: images, containers, Dockerfiles, volumes and networking, in your browser with no install.KubernetesLearn Kubernetes free with hands-on kubectl lessons and a certificate: Pods, Deployments, Services and debugging, in your browser. No cluster needed.CSSLearn CSS free with interactive lessons, live browser previews, AI hints, and a certificate. Selectors, the box model, flexbox, grid - runs in your browser.LuauLearn Luau free with interactive lessons, AI hints, and a certificate. Type annotations, typed tables, unions, generics - Roblox's Lua dialect, in your browser.RobloxLearn Roblox scripting free. Write Lua scripts for lava floors, coins, leaderboards and an obby, then play each game in your browser. No Roblox Studio needed.Next.jsLearn Next.js free with interactive lessons and a certificate: routing, layouts, server and client components, data fetching and server actions.SwiftUILearn SwiftUI free with interactive lessons and a certificate: views, stacks, @State, lists and navigation, with a live preview. No Mac or Xcode needed.Data & PlotsLearn NumPy, pandas and matplotlib by making real charts: arrays, tables, line, scatter, bar and histogram plots, built-in datasets. Free, in your browser.Statistics for MLStatistics for machine learning and data science, taught with Python simulations and charts: spread, distributions, correlation, p-values, scaling. Free.Supervised LearningLearn supervised learning in Python with scikit-learn: classification and regression, k-NN, trees, random forests, pipelines. A chart in every lesson. Free.Unsupervised LearningLearn unsupervised learning hands-on: k-means, hierarchical clustering, DBSCAN, PCA and anomaly detection with scikit-learn. A chart in every lesson. Free.
Learning paths
Several courses in the order a mentor would teach them, for a role rather than a language. Every step is a free course with its own certificate.
DevOpsLinux, Git, Docker, Kubernetes, SQL and Python, in the order the job needs them.Backend DeveloperPython, SQL, Linux, Git and Docker, before any framework.Software EngineerPython, Linux, Git, SQL, data structures and algorithms, then code others can read.Data AnalystExcel, SQL, Python, NumPy and Pandas, in the order the job uses them.Frontend DeveloperHTML, CSS, JavaScript, TypeScript, React and Next.js, then real projects.Computer NetworkingThe OSI model, IP addressing and subnetting, real terminal tools and LAN labs.Data Structures & AlgorithmsTen data structures, eight sorts, recursion, DP, graphs, then interview practice.Full Stack DeveloperThe page, the server and the database: JavaScript, React, Next.js and SQL.MERN Stack DeveloperMongoDB, Express, React and Node.js, from the first page to a secured API.Roblox Game DeveloperRoblox scripting and seven complete Roblox games.Unity Game DeveloperC#, Unity scripting and ten 3D games.Flutter App DeveloperDart, Flutter and four complete phone apps.iOS App DeveloperSwift, SwiftUI and interview practice in Swift.Data ScientistPython, SQL, statistics and machine learning.Python Game DeveloperPython and pygame, from a first window to a platformer.Godot Game DeveloperGDScript, Godot and four 2D games.
Math
From arithmetic to trigonometry, worked out step by step.
View allPre-AlgebraLearn pre-algebra free by solving each problem yourself: integers, fractions, decimals, percents and expressions, on a board that checks every line.AlgebraLearn algebra free by actually solving: equations step by step on an interactive board, then inequalities, absolute value, graphs and systems.GeometryFree interactive geometry lessons: angles, triangles, proofs, polygons, circles, transformations and volume, every step checked on the figure.Algebra 2Learn Algebra 2 free by solving every problem yourself: functions, quadratics, complex numbers, polynomials, radicals and logs, checked line by line.TrigonometryLearn trigonometry free by solving every problem yourself: sin, cos and tan, the unit circle, graphs, identities and the laws of sines and cosines.
Physics
Physics from forces to gravity, solved step by step.
View allMechanicsLearn mechanics by solving real problems: forces and Newton's laws, friction, inclines, motion, projectiles, energy, momentum, circular motion and gravity.Electricity and MagnetismLearn electricity and magnetism by solving real problems: Coulomb's law, fields, capacitors, circuits, Kirchhoff's laws, magnetic forces and induction.Optics, Waves and Modern PhysicsLearn optics, waves and modern physics by solving real problems: reflection, refraction, lenses, interference, photons, the Bohr atom and radioactive decay.
Chess
From the rules to tactics, checkmates and endgames.
View allFundamentalsLearn the rules of chess free on an interactive board: how the board is set up, how every piece moves and captures, check, checkmate, castling and en passant.TacticsChess tactics for beginners, free and on an interactive board: hanging pieces, the fork, the pin, skewers, discovered attacks, mating patterns and mate in two.Playing Real GamesBeginner chess strategy, free and interactive: think before you move, opening principles, your first system as White and Black, and your first whole games.Basic MatesLearn how to checkmate with the pieces you have left: two rooks, king and queen, king and rook, two bishops - and the stalemate alarm that must ring first.The King and the PawnLearn king and pawn endgames free: what can mate and what cannot, the opposition, the rule of the square, key squares, and why a rook pawn so often draws.Checkmate Patterns ILearn the named checkmate patterns free: back rank, support mate, smothered mate, hook, Anastasia's mate, ladder and rook roller, then mate-in-two drills.Core MotifsLearn the core tactical motifs of chess free: the fork, the pin, the skewer, the discovered attack, double check and trapped pieces, drilled from real games.
How it works
Three steps from your first line of code to a certificate you can show off.
- 01
Pick a language
Choose any of our supported programming languages: Python, JavaScript, Java, C++, SQL, and more. No card, no signup wall.
- 02
Learn by writing real code
Every lesson runs in your browser. Type real code, hit run, and see the output. AI hints help when you get stuck.
- 03
Earn a free certificate
Finish the course to unlock a verifiable certificate with a unique ID. Share it on LinkedIn, your CV, or your portfolio.
Our roadmap is public
Every journey and course on Coddy, and what we're building next, is listed on GitHub. Star it to follow along, and open an issue to request a course or suggest a change.
See the roadmap on GitHubFrequently asked questions
Which programming language should I learn first?
It depends on your goal. Python is the easiest entry point and great for data, automation, and AI. JavaScript is the language of the web. Java and C# are strong choices for enterprise and Android. C++ is the standard for performance-critical work. If you have no specific target, start with Python: it's the gentlest ramp from zero to writing real code.
Are these courses really free?
Yes. Every course on Coddy is free: interactive lessons, coding exercises, AI hints, and the certificate at the end. There is no paywall to start, no signup wall to read content, and no card required to earn the certificate.
Do I need to install anything to take these courses?
No. Every exercise compiles and runs in your browser: Python, JavaScript, Java, C++, SQL, and the rest. There is no IDE to set up, no compiler to install, no project to configure. Open the lesson and start coding.
How long does it take to complete a course?
Most learners finish a language in 4-8 weeks of daily practice (around 30 minutes a day). The exact length depends on the language and your starting point. Coddy is designed for short, frequent sessions, so you can fit it around school or work.
Do I get a certificate at the end?
Yes. Every course awards a free certificate when you finish. Each certificate has a unique ID and public verification URL, so recruiters and employers can confirm it is genuine. Add it to LinkedIn, your CV, or your portfolio.
Can I take multiple courses at once?
You can. Many learners pair a primary language (like Python or Java) with a complementary one (like SQL for data work, or JavaScript for the web). Your progress is tracked separately for each course.
