Tutorial

A classic guide that groups and explains Python's special (dunder) methods such as __init__, __getattr__ and __enter__ with examples. in Programming Languages →

Ned Batchelder’s classic talk on Python’s model of names and values. in Programming Languages →

Explains each concept through one annotated program. in Programming Languages →

Google’s short Python course made for its own staff: notes, lectures and exercises. in Programming Languages →

Long, orderly lecture series on .NET, C# and SQL Server. 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 →

The community-maintained online edition of the best-known Haskell introduction. in Programming Languages →

Teaches Python, SQL and R through runnable examples, opening each concept with one small piece of code. in Programming Languages →

A long series building an interpreter step by step in Python, constructing every piece by hand from lexing to the abstract syntax tree. in Programming Languages →

A tiny compiler of a few hundred heavily commented lines. in Programming Languages →

A series writing a C compiler piece by piece. in Programming Languages →

A collection of surprising and counter-intuitive Python behaviours, each as a short snippet with an explanation. in Programming Languages →

A classic front-to-back treatment of C. Comprehensive, but dated in style and examples — handier for looking one topic up than for reading through. in C, C++ & Rust →

C material split by topic. Unlike a sequential book, a search lands you straight on the relevant page; some examples… in C, C++ & Rust →

A collection of solved C programs. Unlike tutorials it offers working examples instead of exposition — handy for recalling a pattern quickly. in C, C++ & Rust →

A step-by-step tutorial that goes from a bootloader up to a kernel, one short folder per step. in C, C++ & Rust →

The official book on async/await and the Future model in Rust. in C, C++ & Rust →

A free book on writing a simple x86 operating system from scratch: booting, memory, interrupts, system calls. in C, C++ & Rust →

Rust’s official book, building up ownership and borrowing from nothing. in C, C++ & Rust →

A one-page tutorial on writing a virtual machine for the LC-3 architecture in C, ending with real LC-3 programs running. in C, C++ & Rust →

One of the largest archives of worked, up-to-date tutorials for Java and Spring. in Java & JVM →

Oracle’s current, official Java learning portal. in Java & JVM →

Oracle’s official Java tutorial, from language basics through collections and concurrency. in Java & JVM →

A free resource explaining design and rendering patterns for modern web apps with examples. in Web & Frontend →

In-depth articles, books and practical guides on web design and development. in Web & Frontend →

Works the language front to back without skipping the hard parts: prototype chain, event loop, promises. in Web & Frontend →

A YouTube channel explaining web development from basics to advanced, simply. in Web & Frontend →

Google’s guides and measurement tools for web quality — performance, accessibility, PWA. in Web & Frontend →

A resource list focused on learning the CSS language and its modules — Flexbox, Grid, selectors. in CSS & UI Kits →

A step-by-step tutorial that builds a blog with Django, written for workshops but followable alone. in Backend, API & System Design →

Collects current PHP practice — Composer, PSR standards, prepared statements. in Backend, API & System Design →

Presents each design pattern as a diagram, a realistic scenario and code — in six languages. in Backend, API & System Design →

Breaks down real company architectures as case studies with actual numbers and the trade-offs taken. in Backend, API & System Design →

Miguel Grinberg’s long, project-based Flask tutorial covering authentication, databases and deployment. in Backend, API & System Design →

A knowledge base for rooting Android with 600+ apps, Magisk/KernelSU/APatch/LSPosed modules and device-specific guides. in Mobile & Desktop →

Paul Hudson’s site teaching Swift and SwiftUI through projects, known for its free “100 Days” courses. in Mobile & Desktop →

In-depth mobile-development tutorials for iOS, Android and Flutter (formerly raywenderlich). in Mobile & Desktop →

Books (Advanced Swift, Thinking in SwiftUI) and the Swift Talk video series on advanced Swift and iOS. in Mobile & Desktop →

A community publication of advanced Android-engineering articles. in Mobile & Desktop →

John Sundell’s in-depth articles and podcast on Swift. in Mobile & Desktop →

Markus Winand’s site teaching modern SQL features such as window functions across dialects. in Databases →

Works MySQL end to end over a sample database, treating join types, subqueries and stored procedures separately. in Databases →

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

A PostgreSQL tutorial showing each topic with a runnable query. 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 →

Markus Winand’s developer-focused guide to SQL indexing and performance. in Databases →

A practice site with 25 real bugs planted inside for you to find. in Testing & QA →

A series of challenges, tutorials and references for practising API testing, by Alan Richardson (EvilTester). in Testing & QA →

A zero-setup test API that returns realistic fake JSON on request. in Testing & QA →

A hub bringing together community, learning resources and events for software testers. in Testing & QA →

A large, deeply nested REST API serving Pokémon data — popular for tests and tutorials. in Testing & QA →

A sample shopping site with ready logins for learning automation; some users deliberately misbehave. in Testing & QA →

Applitools’ free catalogue of test-automation courses by expert instructors, with separate paths for Selenium, Cypress, Playwright and API testing. in Testing & QA →

A site exposing the traps that trip up automation on the modern web (delayed load, hidden elements, dynamic ids). in Testing & QA →

Rigorous, step-by-step Unity C# tutorial series that reach advanced topics such as a custom render pipeline and procedural meshes. in Game Development →

Robert Nystrom’s free book on the design patterns that recur in game code. in Game Development →

A comprehensive, well-ordered tutorial teaching modern OpenGL from scratch. in Game Development →

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

A simple, beginner-friendly C library for games that starts you fast with few dependencies. in Game Development →

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

A site of resources, tutorials and tools for reverse-engineering retro games — source leaks, hardware, decompilation. in Game Development →

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

An agent that places phone calls from an API call, showing the speech-recognition → model → synthesis chain end to end. in AI · Agents & Infrastructure →

A repo collecting what does and does not work when pairing with a coding agent — field notes rather than official docs. in AI · Agents & Infrastructure →

The official walkthrough of defining tools, binding a model and wiring the loop. in AI · Agents & Infrastructure →

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

Application-focused ML tutorials, each ending in working code — answering “how do I do this” rather than the theory. in Data Science & ML →

Free lecture notes on the scientific Python stack — NumPy, SciPy, Matplotlib. in Data Science & ML →

A free community offering hands-on data-engineering and ML zoomcamps. in Data Engineering →

A deep document on how Apache Spark works inside — scheduling, shuffle, memory. in Data Engineering →

Brendan Gregg's page on the flame graph visualisation: how to read one, the CPU/memory/off-CPU variants, generation tools and talks. in DevOps & Infrastructure →

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

Kelsey Hightower's guide to bootstrapping a Kubernetes cluster by hand, component by component, without automation. in DevOps & Infrastructure →

The official six-step series on queue patterns — work queues, pub/sub, routing, RPC. in DevOps & Infrastructure →

A Mozilla article that uses cartoons to explain why DNS is a privacy problem and how DoH changes it. in Networking & Sysadmin →

An introduction to shell scripting. Unlike the Advanced Bash-Scripting Guide, it lays the groundwork without that guide’s weight. in Networking & Sysadmin →

A Bash guide centred on the most common mistakes, such as quoting and word splitting. in Networking & Sysadmin →

First-time setup of one specific switch model, screenshot by screenshot. in Networking & Sysadmin →

A step-by-step guide to building a root and intermediate certificate authority with OpenSSL, signing certificates and publishing revocation lists. in Networking & Sysadmin →

An introduction to Linux and Bash with exercises closing every section. in Networking & Sysadmin →

Community-maintained Turkish wiki covering Ubuntu and GNU/Linux system administration, package management, networking… in Networking & Sysadmin →

End-to-end recipes for building a highly-available “private cloud” on Docker Swarm. in Self-Hosting & Personal Cloud →

A large guide to hosting your own services (home and cloud), packed with software and tool links. in Self-Hosting & Personal Cloud →

A large tutorial repository for the Flipper Zero covering apps, hardware add-ons and usage. in Hardware, CAD & Embedded →

Projects that introduce FPGAs through hardware description languages, each producing a working circuit. in Hardware, CAD & Embedded →

The flashing steps and, more importantly, the way back. in Hardware, CAD & Embedded →

Open-source hardware plus a huge library of beginner-friendly learning guides for every board. in Electrical & Electronics →

Step-by-step, illustrated guides for microcontroller, sensor and electronics projects. in Electrical & Electronics →

Free lessons, calculators and a forum teaching electrical and electronics from the ground up. in Electrical & Electronics →

A free archive teaching electronics fundamentals — resistors, capacitors, transistors, op-amps — step by step with the formulas. in Electrical & Electronics →

Worked electronics projects and tutorials with schematics and code. in Electrical & Electronics →

A hardware community sharing step-by-step IoT and embedded projects. in Electrical & Electronics →

A maker-electronics store with an extensive project-based tutorial system tied to each module. in Electrical & Electronics →

A tutorial library for electronics basics and embedded projects. in Electrical & Electronics →

Browser 3D design plus circuit and Arduino simulation — an electronics playground for beginners. in Electrical & Electronics →

A step-by-step build starting from components rather than a kit. in Smart Glasses & Wearables →

A step-by-step build guide for open-source smart glasses with a bill of materials and assembly order. in Smart Glasses & Wearables →

A community guide to hardening macOS step by step: FileVault, firewall, DNS, VPN and app permissions. in Privacy & Personal Security →

The Electronic Frontier Foundation's guide to protecting communications and devices against surveillance, from building… in Privacy & Personal Security →

A guide gathering OSINT techniques the usual tool lists skip — blockchain tracing, metadata, unconventional sources. in Offence, Defence & OSINT →

A knowledge base giving pentest, red-team, web, cloud and privilege-escalation techniques as step-by-step commands. in Offence, Defence & OSINT →

A resource set covering every branch of offensive security — infrastructure, wireless, IoT, exploit development, cloud — together with labs. in Offence, Defence & OSINT →

A downloadable, deliberately vulnerable app containing 100+ web vulnerabilities. in CTF & Hands-on Labs →

A step-by-step solution of the internet’s best-known puzzle, chaining steganography, book ciphers and Tor hidden services. in CTF & Hands-on Labs →

A modern, vulnerability-filled web app practice target built by PortSwigger. in CTF & Hands-on Labs →

Google’s “full of holes” codelab teaching web application flaws. in CTF & Hands-on Labs →

HackerOne's free video lessons and CTF on finding web vulnerabilities; flags earned can bring invitations to private bug bounty programs. 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 →

A modern web app deliberately full of vulnerabilities — a target for learning security. in CTF & Hands-on Labs →

Arizona State University's free cybersecurity education platform; beginner-friendly modules with in-browser practice… 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 →

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

A technical account of how a homophonic substitution cipher unsolved for fifty-one years was broken — a real worked… in CTF & Hands-on Labs →

A brief intro to LaTeX for beginners, in minutes. in Science & Academia →

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

A resource opening the places people get stuck moving into abstract mathematics — reading definitions, the language of proof, notation. in Mathematics →

Olympiad-level competition-math courses and a forum community. in Mathematics →

A set of essays explaining maths by intuition rather than memorisation — exponentials, Euler’s formula, calculus. in Mathematics →

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

Jeremy Kun’s blog joining mathematics with working code — cryptography, graphs, the maths of machine learning. in Mathematics →

An approachable graduate-maths blog that builds intuition for abstract topics. in Mathematics →

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

Clean, worked lecture notes for algebra, calculus and differential equations (Lamar University). in Mathematics →

An equation solver that shows the worked steps to a solution, derivatives, integrals and limits included. in Mathematics →

Installing Q# and the QDK; the VS Code extension is the shortest path to running circuits on a local simulator. in Quantum Computing →

IBM’s open-source quantum programming framework, giving access to real quantum hardware. in Quantum Computing →

An education project explaining quantum concepts at three separate depths: game, animation and technical account. in Quantum Computing →

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

Open-source lectures and libraries for computational economics (Python and Julia). in Economics →

An encyclopedia explaining finance and investing terms dictionary-style, with worked examples. in Finance, Markets & Crypto →

Explains Bitcoin’s technical workings — transaction structure, script, mining — through worked examples. in Finance, Markets & Crypto →

An architecture site giving competitions, software and learning content alongside project news. in Architecture & Building →

Articles and tutorials teaching urban data, mapping and generative design. in Architecture & Building →

Independent archive of code-heavy tutorials covering C++, Python, Linux systems programming, sockets, algorithms, and… in Learning & Roadmaps →

A "crash course" series summarising a language or framework in a single video. in Learning & Roadmaps →

The University of Helsinki’s introduction to AI, requiring no mathematics and available in many languages including Turkish. in Learning & Roadmaps →

The University of Helsinki’s free, end-to-end full-stack course teaching React, Node and GraphQL. in Learning & Roadmaps →

A colourful comic that shows how a DNS query is resolved through resolvers, root and TLD servers. in Learning & Roadmaps →

A one-page comic that explains HTTPS, certificates and key exchange. in Learning & Roadmaps →

A short book by curl's author Daniel Stenberg explaining the HTTP/2 protocol, including headers, streams and server push. in Learning & Roadmaps →

A step-by-step tutorial that builds a SQLite-like database from scratch in C: REPL, B-tree, pager, cursors. in Learning & Roadmaps →

A community guide to server setup, networking, security and service configuration on the Rocky/RHEL family, step by step. in Learning & Roadmaps →

The Linux Professional Institute's official study materials for the Linux Essentials and LPIC exams, openly licensed and free. in Learning & Roadmaps →

Course slides built from Markdown for React, Vue, Python, data science, HTML/CSS, JavaScript/TypeScript and databases, with exercises and solutions. in Learning & Roadmaps →

MIT’s open archive of lecture notes, assignments, exams and solutions. in Learning & Roadmaps →

A page that walks through every byte of a TLS 1.2 handshake with colour-coded, annotated and hand-computed values. in Learning & Roadmaps →

A large archive of tutorials in short episodes across many languages and technologies. in Learning & Roadmaps →

Short tutorial series for hundreds of technologies. in Learning & Roadmaps →

A detailed step-by-step account of everything that happens when you type an address in a browser and press Enter (DNS, TCP, TLS, HTTP, rendering). in Learning & Roadmaps →

A practice-heavy course teaching Java through 1,200 hands-on tasks, with every solution checked automatically. in Practice & Challenges →

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

Structured courses for system-design and algorithm interviews. in Practice & Challenges →

Teaches programming through many small exercises, designed for a high-school-level start. in Practice & Challenges →

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

A spec whose same realistic app (Conduit) is built across different front-end and back-end stacks. in Practice & Challenges →

An organised, interactive space of topic tutorials and practice for aspiring programmers. in Practice & Challenges →

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

A long-standing site with detailed tutorials on Unix tools such as sed, awk, csh and regular expressions. in Cheat Sheets & Quick Reference →

A one-page introduction to Git’s basic flow, going as far as branching, merging and remotes. in Cheat Sheets & Quick Reference →

A long single-page AWK tutorial taught from scratch with examples. in Cheat Sheets & Quick Reference →

A tutorial on grep, egrep and fgrep and regular expression syntax, with examples. in Cheat Sheets & Quick Reference →

A single-page sed tutorial built around addresses, commands and regular expressions. in Cheat Sheets & Quick Reference →

Julia Evans' page of drawings and zines that explain Linux, networking, debugging tools and systems concepts. in Cheat Sheets & Quick Reference →

Introduces a language through a single annotated file. in Cheat Sheets & Quick Reference →

A compact collection of command-line tips split into everyday, advanced and situational sections, translated into dozens of languages. in Cheat Sheets & Quick Reference →

A web reference with runnable examples. Less rigorous than MDN and occasionally out of date, though the “Try it” editor… in Cheat Sheets & Quick Reference →

A guide comparing methods for archiving a site offline — wget, HTTrack and the rest. in Productivity & Everyday Tools →

An introduction for people making their first open-source contribution, aimed squarely at reducing the fear. in Open Source & Contributing →

GitHub’s guides to open source: starting a project, taking contributions, running a community, handling burnout. in Open Source & Contributing →

A free blogging and discussion community for programmers. in Lists, Directories & Discovery →

A community guide to how private torrent trackers work and how to get in. in Piracy →

A community guide to getting started with Usenet and choosing providers and indexers. in Piracy →