Interactive

Go’s official tour, with every example runnable and editable in the browser. in Programming Languages →

Runnable JavaScript exercises in the browser. in Programming Languages →

An interactive introduction teaching Python through in-browser exercises, with nothing to install. in Programming Languages →

An introduction to shell scripting through exercises that run in the browser. in Programming Languages →

A C tutorial you compile and run in the browser. in C, C++ & Rust →

The official resource giving each concept as a runnable, editable code example. in C, C++ & Rust →

The official space to compile and run Rust code in the browser with no install. in C, C++ & Rust →

An exercise set teaching Rust by fixing small, broken snippets. in C, C++ & Rust →

A practice platform that gives realistic design files and asks you to turn them into code. in Web & Frontend →

A game where you reproduce a target image with as little CSS code as possible. in CSS & UI Kits →

A reference showing every CSS property with a visual example. in CSS & UI Kits →

The Flexbox sibling of Grid Garden, teaching alignment by positioning frogs. in CSS & UI Kits →

A 28-level game teaching CSS Grid by watering carrots. in CSS & UI Kits →

A tool to draw a CSS Grid layout by drag-and-drop and generate its code. in CSS & UI Kits →

A complete game development environment in the browser: code editor, sprite drawing, map editor and sound generation together. in Mobile & Desktop →

Amazon’s Lumberyard, handed to the Linux Foundation as an Apache 2.0 modular 3D engine. in Mobile & Desktop →

An indie developer’s devlog alongside an OpenGL tutorial series. in Mobile & Desktop →

The engine behind AAA productions, offering real-time high-density geometry and global illumination through Nanite and Lumen. in Mobile & Desktop →

Practise SQL with graded PostgreSQL exercises in the browser. in Databases →

An interactive online book that teaches SQL through exercises run in the browser against one real dataset. in Databases →

Interactive SQL lessons that teach by doing in the browser; each lesson ends with an exercise where you write the query. in Databases →

An exercise set that teaches SQL by making you write queries in the browser, each section over its own dataset. in Databases →

A list of target sites and APIs for practising test automation: demo shops, forms, trap-laden pages and fake APIs, grouped by kind. in Testing & QA →

An online practice that builds SQL proficiency with challenging problems. in Testing & QA →

A classic practice site collecting the common scenarios that challenge automation (iframes, file upload, hovering menus) one by one. in Testing & QA →

A resource list for Babylon.js, a 3D game engine for web and native. in Game Development →

A resource list for Flame, the game engine for Flutter. in Game Development →

A list of actively maintained, open-source remakes of classic games. in Game Development →

A list of games that teach a programming language by making games. in Game Development →

A list of plugins, tutorials and example projects for the open-source Godot engine. in Game Development →

Course, book and community resources for learning to make games. in Game Development →

A list of libraries and resources for libGDX, the Java game framework that targets desktop, Android, iOS and web from one codebase. in Game Development →

A list of resources and libraries for LÖVE, the Lua-based game engine. in Game Development →

A list gathering Minecraft server software, mods, launchers and tools. in Game Development →

A list of playable games whose source is open. in Game Development →

A list of libraries and tutorials for OpenGL, the 2D/3D rendering API. in Game Development →

A list of games and tools for PICO-8, the retro-constrained fantasy console. in Game Development →

A resource list for Vulkan, the low-overhead 3D graphics and compute API. in Game Development →

Formerly Gamasutra — industry articles and game-development postmortems. in Game Development →

An MIT-licensed game engine with separately mature 2D and 3D pipelines. in Game Development →

An open, pay-what-you-want marketplace for indie games, tools and assets. in Game Development →

A Lua framework for 2D games, well suited to fast prototyping. in Game Development →

Tutorials explaining game-dev maths — A*, hex grids, field of view — through interactive visuals. in Game Development →

A gentle, interactive introduction to fragment shaders (GLSL). in Game Development →

A browser surface for testing prompts, setting system instructions and fiddling with temperature. in AI · Models & Assistants →

An LLM tracing and evaluation tool that runs inside a notebook and renders traces locally. in AI · Agents & Infrastructure →

Speeds up sequence alignment with MMseqs2 to make AlphaFold runnable in Colab. in AI · Applied Tools →

Jupyter in the browser with a free T4 GPU. in AI · Applied Tools →

Notebooks sitting on the same platform as the datasets, with a weekly GPU quota more predictable than Colab’s. in AI · Applied Tools →

An image-generation platform. Unlike Midjourney you can train a style model on your own images and reuse it — decisive… in AI · Generative Media →

Tools from the foundation Hans Rosling co-founded, presenting global development data through fact-based visualisations. in Data Science & ML →

Bite-sized micro-courses covering Python, Pandas, SQL, and machine learning through in-browser notebook exercises… in Data Science & ML →

Active and past competitions. Unlike working on your own project, you are scored against a real metric on a hidden test… in Data Science & ML →

Interactive WebGL map clustering subreddits by shared commenters (2020-21 comments). in Data Science & ML →

Amazon’s set explaining machine learning concepts through interactive visuals. in Data Science & ML →

End-to-end ML notebooks walking a working pipeline from data cleaning to model evaluation, progressing through real code rather than concept prose. in Data Science & ML →

Runs an Android emulator in a container with VNC access to the screen. in DevOps & Infrastructure →

Renders repository history as a growing animated tree where you see who touched what. in DevOps & Infrastructure →

Hands-on labs and challenges teaching Linux, containers, Kubernetes and networking in real VMs inside the browser. in DevOps & Infrastructure →

Teaches Linux in small modules — filesystem, permissions, processes, package management. in Networking & Sysadmin →

A map rendering power lines, plants, oil/gas pipelines and telecom infrastructure from OpenStreetMap data. in Networking & Sysadmin →

The Packet Tracer download plus lab files, letting you practise VLAN, OSPF and ACL configuration without buying switches and routers. in Networking & Sysadmin →

Simulates working a real helpdesk queue — prioritisation, escalation, SLA tracking. in Networking & Sysadmin →

TeleGeography's interactive map of the world's submarine internet cables, landing points and owners. in Networking & Sysadmin →

Circuit simulation with real-time animation, working on mobile as well. in Hardware, CAD & Embedded →

A simulator that lets you draw a circuit in the browser and shows current and voltage as a live animation. in Electrical & Electronics →

A user-submitted archive of reverse engineering challenges (crackmes), filterable by difficulty, language and platform. in CTF & Hands-on Labs →

A Google-built test target hosting many application-security issues. in CTF & Hands-on Labs →

Every challenge from Google’s CTF competitions, with source code and solutions. in CTF & Hands-on Labs →

Realistic machines with no hints — reconnaissance and research are entirely on you. in CTF & Hands-on Labs →

Module-based learning with practical certifications such as CPTS and CBBH. in CTF & Hands-on Labs →

A long-running site with basic hacking missions (basic, realistic, programming, stego) in a legal, safe setting. in CTF & Hands-on Labs →

A developer-oriented site that explains common web vulnerabilities (XSS, SQL injection, CSRF) in short interactive lessons. in CTF & Hands-on Labs →

Hands-on, in-browser labs covering penetration testing and web security. in CTF & Hands-on Labs →

An embedded-systems CTF where you break electronic locks using an in-browser MSP430 debugger. in CTF & Hands-on Labs →

Carnegie Mellon's free CTF platform with web, crypto, reverse engineering and forensics tasks. in CTF & Hands-on Labs →

A non-profit wargame site for binary exploitation (pwn), starting at the Toddler's Bottle tier and getting harder. in CTF & Hands-on Labs →

Harder binary exploitation tasks aimed at building pwn skills on near-real vulnerabilities. in CTF & Hands-on Labs →

A community-run French platform with hundreds of challenges and virtual environments across web, cryptography, reverse engineering and forensics. in CTF & Hands-on Labs →

Guided labs that explain which tool you are using and why in each room. in CTF & Hands-on Labs →

An archive of community-built vulnerable VMs you download and run locally. in CTF & Hands-on Labs →

PortSwigger’s free, hands-on web-security course — a live lab for each vulnerability. in CTF & Hands-on Labs →

Hands-on labs and mock exams for security certifications — preparation by actually running the tools rather than memorising a question bank. in Certification & Career →

A tool that starts from one paper and builds a visual graph of related work. in Science & Academia →

Visualisation of global wind, ocean-current and air-pollution forecasts on a live globe. in Science & Academia →

The University of Colorado’s interactive simulations for physics, chemistry and maths. in Science & Academia →

Explores Wikipedia’s link network as a graph. in Science & Academia →

Grant Sanderson’s channel and site explaining mathematics through animation — linear algebra, calculus, analysis. in Mathematics →

A free online graphing calculator producing fast, shareable interactive graphs. in Mathematics →

Dynamic maths software that links geometry, algebra and calculus live. in Mathematics →

A site teaching mathematics topic by topic with interactive graphs and worked examples. in Mathematics →

A free platform teaching mathematics from primary school to university, with exercises in order. in Mathematics →

A mathematics Q&A site where you can ask experts about the step you are stuck on. in Mathematics →

An interactive maths textbook with manipulable, story-driven lessons. in Mathematics →

A Brown University project teaching probability and statistics entirely through interactive visuals. in Mathematics →

A site teaching quantum computing as a “book” with spaced-repetition built in. in Quantum Computing →

A virtual lab where you assemble and run optical quantum experiments by dragging photons, polarisers and beam splitters. in Quantum Computing →

A browser-based laboratory for designing and simulating quantum optics experiments. in Quantum Computing →

An economics Q&A site where you can ask experts about concepts and models. in Economics →

A free video-and-exercise set teaching the basics of micro, macro and finance from scratch. in Economics →

Free economics education platform founded by Tyler Cowen and Alex Tabarrok covering micro, macro, trade, and… in Economics →

A university-backed research publication presenting long-run data on the economy, population, health and environment as interactive charts. in Economics →

An analytics platform where the community builds dashboards with SQL queries over blockchain data. in Finance, Markets & Crypto →

A visual stock screener that scans the US market on one screen with a heatmap and dense filters. in Finance, Markets & Crypto →

Bloomberg-like analytics dashboards for equities and macro, offered with a generous free tier. in Finance, Markets & Crypto →

Free long-term charts of stocks and economic data going back decades. in Finance, Markets & Crypto →

Runs portfolio backtesting, Monte Carlo simulation and factor analysis in the browser. in Finance, Markets & Crypto →

Classifies game interfaces by screen type — inventory, map, settings, loading. in UI Design, Colour & Type →

An editor built for pixel art and animation, with onion skinning, a frame timeline and sprite sheet export. in Media, Files & Diagrams →

A real-time, infinite whiteboard for diagrams and brainstorming. in Media, Files & Diagrams →

Browser-based piano-roll sequencer for composing multi-track melodies and exporting MIDI files with zero setup; built… in Media, Files & Diagrams →

A tool combining flowcharts, wireframes, sticky notes and mind maps on one canvas. in Media, Files & Diagrams →

A platform that visualises an algorithm step by step alongside its code, and runs code you write yourself. in Learning & Roadmaps →

A backend-focused curriculum with in-browser exercises. in Learning & Roadmaps →

A game teaching CSS selectors by picking dishes on a table. in Learning & Roadmaps →

The classic collection of step-by-step animations for data structures and algorithms, from red-black trees to Dijkstra. in Learning & Roadmaps →

Short video then in-browser coding with instant grading. in Learning & Roadmaps →

A research journal explaining machine-learning ideas through interactive visuals. in Learning & Roadmaps →

A platform teaching languages through gamified, short daily lessons. in Learning & Roadmaps →

A site teaching CSS Flexbox through a tower-defence game. in Learning & Roadmaps →

A free curriculum covering algorithms, cryptography and information theory through interactive lessons. in Learning & Roadmaps →

A browser visualisation that animates how SHA-256 turns an input into a hash, showing the bits in memory and each round. in Learning & Roadmaps →

A game that teaches the basics of programming by trial and error, with no word of explanation. in Learning & Roadmaps →

A platform teaching programming on mobile through small lessons and community. in Learning & Roadmaps →

Generates quick quizzes in maths and basic subjects and collects results. in Learning & Roadmaps →

Unity’s official training, updated in step with the engine. in Learning & Roadmaps →

Lays out the skills to learn as a web developer (HTML, CSS, JS, tooling, testing, performance) as a visual map, with… in Learning & Roadmaps →

A typing speed test on a Turkish word list, saving results so you can track progress. in Practice & Challenges →

One puzzle a day each December, with the archive open year round. in Practice & Challenges →

A Japan-based contest platform whose beginner rounds (ABC) are more approachable for newcomers than Codeforces. in Practice & Challenges →

An online judge grading programming, mathematics and SQL problems automatically, formerly URI Online Judge. in Practice & Challenges →

In-browser lessons across 15+ languages. Because everything runs in the browser instead of a local setup, it removes… in Practice & Challenges →

A community contest to solve a problem in the shortest possible code. in Practice & Challenges →

A problem sequence starting at the very easiest and climbing gradually — a far gentler curve than the contest platforms for absolute beginners. in Practice & Challenges →

A competitive algorithm platform with regular contests, difficulty-tagged problems and published editorial solutions. in Practice & Challenges →

The busiest competitive programming platform, with regular rounds and a rating system. in Practice & Challenges →

Front-end (HTML/CSS/JS) challenges with an embedded editor, each round on a new theme. in Practice & Challenges →

An interview problem bank and assessment tool. in Practice & Challenges →

Practice gamified with martial-arts ranks. in Practice & Challenges →

A platform that has you solve programming puzzles with a game theme, showing your code’s result in a game scene. in Practice & Challenges →

RPG-themed learning that sustains motivation with XP and map progress. in Practice & Challenges →

Teaches cryptography by breaking it, with each level exploiting a real weakness. in Practice & Challenges →

A visualisation tool built for Georgia Tech’s data structures course — narrower than VisuAlgo but aligned exactly to a syllabus. in Practice & Challenges →

A challenge site that has you build web projects with realistic designs and requirements. in Practice & Challenges →

Small, fast puzzles targeting language fluency rather than algorithm theory — better than LeetCode for settling syntax when you move to a new language. in Practice & Challenges →

Exercise-based practice in 70+ languages, with volunteer mentors commenting on your solution. in Practice & Challenges →

Language-independent definitions and test data for Exercism’s exercises. in Practice & Challenges →

A complete free curriculum with in-browser exercises and free certificates. in Practice & Challenges →

Run Git commands in a safe environment with immediate feedback. in Practice & Challenges →

A practice tool where you answer interview questions aloud and get AI feedback. in Practice & Challenges →

Touch-typing practice that measures which letters you struggle with and generates text accordingly. in Practice & Challenges →

Spins up a real Linux or Kubernetes machine in the browser — not a simulation. in Practice & Challenges →

Draws the commit graph live to show what rebase, cherry-pick and merge actually do — the shortest path to learning Git… in Practice & Challenges →

Turkish touch-typing training supporting F and Q layouts separately. in Practice & Challenges →

Free, peer-to-peer mock technical-interview practice, now part of Exponent. in Practice & Challenges →

A riddle game where each level is solved with a bit of Python. in Practice & Challenges →

A repository that teaches Python by making failing tests (“koans”) pass one at a time. in Practice & Challenges →

Steps through code drawing stack frames and heap objects. in Practice & Challenges →

Peter Norvig’s short Python programs and notebooks on puzzles, algorithms and language. in Practice & Challenges →

A scenario-based game for learning SELinux that you run on your own machine. in Practice & Challenges →

A Python 3 course with 100+ exercises, coded in the browser. in Practice & Challenges →

A long-running online judge with a large archive of classic algorithm problems. in Practice & Challenges →

One of the oldest competitive programming platforms; its problem archive and editorials form a slice of algorithm history. in Practice & Challenges →

The classic arena for timed algorithm competitions (SRM). in Practice & Challenges →

An online game to increase your typing speed by racing against others. in Practice & Challenges →

A classic online judge auto-grading hundreds of contest problems. in Practice & Challenges →

Teaches Vim shortcuts through a Zelda-like game — you earn hjkl and motion commands by playing rather than memorising them. in Practice & Challenges →

Animates data structures and algorithms step by step. in Practice & Challenges →

A free book on simulating natural systems in code — forces, particles, flocking, cellular automata — delivering the… in Free Books & Long Reads →

A technical site giving broad comparison tables on operating systems, file systems and countries’ digital freedom. in Cheat Sheets & Quick Reference →

An interactive Python reference that narrows as you search, opening the relevant section as you type. in Cheat Sheets & Quick Reference →

Compares coding fonts two at a time in a tournament until one wins. in Editors, IDEs & Terminals →

Write, run and share C# and .NET code in the browser. in Online Playgrounds & Compilers →

Runs projects with full npm dependencies in the browser. in Online Playgrounds & Compilers →

Real-time collaborative code editing in the browser with no install or account. in Online Playgrounds & Compilers →

Compiles and runs 60+ languages in the browser and accepts an input stream. in Online Playgrounds & Compilers →

An open-source online compiler. Unlike closed services such as Ideone you can self-host its engine — the project people… in Online Playgrounds & Compilers →

An online IDE supporting many languages, with no install. in Online Playgrounds & Compilers →

A collaborative cloud IDE that writes and runs dozens of languages in the browser and can deploy a project in one click. in Online Playgrounds & Compilers →

Runs Node.js in the browser through WebContainers. in Online Playgrounds & Compilers →

A regex tester and an alternative to regex101, with a simpler interface and a community library of patterns. in Converters, Formatters & Checkers →

Draws JavaScript regular expressions as railroad diagrams. in Converters, Formatters & Checkers →

A list of real-time map and data-visualisation sites (aviation, space, weather, history, marine, cyber threats). in Lists, Directories & Discovery →

A visualisation clustering GitHub repositories by star similarity into a browsable map. in Lists, Directories & Discovery →

An open-source analytics platform that analyses 10B+ GitHub events in real time, comparing repositories by stars, commits and contributor health. in Lists, Directories & Discovery →