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Every language here has a learning path you can read in order, exercises that check your answer by running it, and a playground. Where a language runs in your browser, it says so; where it does not yet, the page says that instead.

• SQL

  SQL

  Ask questions of data

  The language of relational databases: reading, filtering, joining and summarising tables. Runs in your browser here on a real SQLite engine.

  Beginner-friendlyRuns in your browser

  Used for: Data analysis, Reporting, Backend development, Data engineering

  32 tutorials · 42 exercises

  Learning pathPractisePlayground
• Py

  Python

  Readable code for almost anything

  A general-purpose language known for clear syntax and a huge standard library. The usual first language for data work, automation and backend services.

  Beginner-friendlyRuns in your browser

  Used for: Data science, Automation and scripting, Web backends, Machine learning

  17 lessons · 9 exercises

  Learning pathPractisePlayground
• JS

  JavaScript

  The language of the web

  Runs in every browser and, with Node.js, on servers too. Event-driven, flexible and everywhere front-end work happens.

  Beginner-friendlyRuns in your browser

  Used for: Front-end web apps, Node.js backends, Browser extensions, Tooling

  19 lessons · 9 exercises

  Learning pathPractisePlayground
• Jv

  Java

  Strongly typed, runs everywhere

  A statically typed, object-oriented language with a mature ecosystem. Common in large backends, Android apps and enterprise systems.

  ModerateExamples verified with OpenJDK 21

  Used for: Enterprise backends, Android apps, Large-scale systems, Big-data tooling

  8 lessons · 0 exercises

  Learning pathPractisePlayground
• C++

  C++

  Performance with abstractions

  A systems language with classes, templates and the Standard Template Library. The language of game engines, high-frequency systems and competitive programming.

  ChallengingExamples verified with GCC 13 (C++17)

  Used for: Systems and games, High-performance computing, Competitive programming, Embedded software

  14 lessons · 0 exercises

  Learning pathPractisePlayground
• C

  C

  Close to the machine

  The small, portable language beneath most operating systems and runtimes. Teaches memory, pointers and how programs really execute.

  ChallengingExamples verified with GCC 13 (C11)

  Used for: Operating systems, Embedded devices, Compilers and runtimes, Performance-critical libraries

  14 lessons · 0 exercises

  Learning pathPractisePlayground
• C#

  C#

  Modern, typed, productive

  Microsoft's object-oriented language for the .NET platform: web services, desktop software and Unity games, with strong tooling.

  ModerateExamples verified with .NET SDK 8.0

  Used for: .NET web services, Desktop apps, Unity games, Enterprise software

  3 lessons · 13 exercises · 13 interview questions

  Learning pathPractisePlayground
• Rs

  Rust

  Memory safety without a garbage collector

  A systems language whose compiler enforces ownership rules, preventing whole classes of memory bugs. Used where C++ was, with more guarantees.

  ChallengingExamples verified with rustc 1.94

  Used for: Systems programming, WebAssembly, Command-line tools, Backends that need speed

  5 lessons · 13 exercises · 12 interview questions

  Learning pathPractisePlayground
• php

  PHP

  The web's workhorse

  A server-side scripting language behind a large share of the web, including WordPress and Laravel applications.

  Beginner-friendlyExamples verified with PHP 8.4

  Used for: Web backends, Content management systems, E-commerce, APIs

  9 lessons · 14 exercises · 12 interview questions

  Learning pathPractisePlayground

In preparation: TypeScript, Go, Kotlin, R. Their learning paths are being written and verified; they will appear here when ready. TypeScript already runs in the playground.