The Best of Low-Cost Learning

freeCodeCamp's flagship JavaScript certification. ~300 hours of interactive challenges covering ES6, regex, debugging, data structures (stack, queue, linked list, tree, graph, hash map), and 5 algorithm projects. Fully browser-based, no install.

Eric Wastl's annual December coding puzzle advent calendar. 25 problems from Dec 1-25, ranging from Easy to Hard. Each problem has a story (saving Christmas, defeating an evil elf, etc.) and a unique solution. Any language, any approach. Community solutions on Reddit and GitHub.

A curated list of free university courses with high-quality materials (assignments, lectures, notes, readings, exams) available online. Covers Algorithms, AI, Computer Graphics, CS Theory, Intro CS, Machine Learning, Programming Languages, Security, Systems, Statistics, and more. Each entry has the school, course title, and links to the actual course materials.

A curated list of GitHub projects that are specifically geared toward beginners — labeled 'good-first-issue' or 'beginner-friendly'. Covers 30+ programming languages and dozens of project domains. Each entry links to a project repo with a clear path for first-time contributors (mentors, labels, easy issues).

UC Berkeley's computer graphics course. Lecture videos (2017 and 2019), slides, and assignments. Covers: transformation matrices, 3D viewing, ray tracing, rasterization, Bézier curves, animation, and modern GPU shader programming. Assignments include building a ray tracer, a Bezier surface editor, and a cloth simulator.

UC Berkeley's intro CS course using Python. The course that SICP inspired, but in Python instead of Scheme. Covers: functions, data abstraction, recursion, higher-order functions, OOP, Scheme, SQL, and the classic SICP-style abstraction challenges. Lecture videos, slides, labs, and homeworks.

UC Berkeley's EECS 70 — the discrete math + probability class for CS students. Lecture videos, slides, and homeworks covering: logic, proofs, modular arithmetic, polynomials, induction, graph theory, counting, probability, random variables, and Markov chains. The right pre-class for algorithms and ML.

Carnegie Mellon's intro CS course using Python. Lecture videos (2016 and 2018), homeworks, and a final project. The homeworks are famously creative: each one is a different interactive graphics project (15-112-style graphics). Covers: Python fundamentals, recursion, OOP, algorithmic thinking, and 2D graphics.

Carnegie Mellon's intro computer systems course — the same one that became the textbook 'Computer Systems: A Programmer's Perspective' (CS:APP) by Bryant and O'Hallaron. Lecture videos (Carnegie Mellon's 2015 recording), labs, and assignments cover: bits, C, machine code, x86-64 assembly, memory hierarchy, linking, exceptions, signals, virtual memory, I/O, concurrency, network programming. The labs include a binary bomb, malloc lab, proxy lab, and shell lab.

Carnegie Mellon's graduate algorithms course. Lecture videos (2015 and 2024) and slides covering: max-flow/min-cut, LP duality, NP-completeness, approximation algorithms, online algorithms, randomized algorithms, and competitive analysis. The actual recordings from Avrim Blum's class.

Gamified coding kata practice. 9,000+ kata (problems) in 60+ languages, ranked by difficulty (8 kyu = beginner, 1 kyu = expert). Earn honor and ranks as you complete kata. Community-driven — anyone can author katas. Free to play, optional paid pro tier with no functional difference.

Cornell's functional programming course using OCaml. Lecture videos (2024), slides, homeworks, and a final project. Covers: functional programming, OCaml, type systems, monads, formal reasoning, and a substantial final project (build a real OCaml app). The same course as the on-campus CS 3110.

UC Berkeley's free computer architecture course. Lecture videos, slides, labs, and homeworks. Covers C, memory, RISC-V, pipelining, caching, virtual memory, parallelism, and I/O. The right starting point for learning how real computers execute code. Same course as the on-campus CS 61C at Berkeley.

The most comprehensive free programming book list, organized by subject. 5,000+ books in 30+ languages. Categories: Algorithms, AI, Blockchain, Cloud, Compilers, Computer Graphics, Computer Organization, Cryptography, Data Science, Game Development, Git, Hacking, Hardware, IDE, Information Retrieval, Math, Misc, Networking, Open Source, Operating Systems, Patterns, Programming Languages, Quantum Computing, Reverse Engineering, Security, Software Architecture, Standards, System Design, Testing, Theory, Web Performance. All books are legal free downloads.

Free programming practice platform with 70+ languages (Python, JavaScript, Rust, Go, C++, Haskell, Lua, COBOL, Prolog, even esoteric languages). 100+ exercises per language with mentor feedback (free mentorship is the killer feature). Tracks range from intro to expert.

A hands-on tutorial for making your first open-source contribution. 15-minute walkthrough that guides you through forking a repo, creating a branch, making a change, and opening a pull request. Designed for absolute beginners. Available in 30+ languages.

A curated list of SaaS, PaaS, and IaaS offerings with free developer tiers. Covers: API/ML services, artifact repos, CDN, CI/CD, code quality, code search, databases, design/UI, email, fonts, Generative AI, IDE, monitoring, PaaS, payments, search, security, SMS, and more. 1600+ contributors, opinionated and well-vetted.

The official GNU Bash manual. The 'Bash Reference Manual' section is the full language reference: syntax, parameters, expansions, builtins, shell variables, job control, history, command-line editing. The 'Bash Features' section is the tutorial-style intro. Free HTML, PDF, and TeX source.

Greg Wooledge's free Bash wiki — the canonical 'how to write good Bash' reference. Covers variables, expansions, conditionals, loops, arrays, functions, parameter expansion, process substitution, traps, and the most common Bash pitfalls. Curated by the Bash community, used by Exercism as the recommended 'learn Bash' path. Companion: BashPitfalls.

Harvard's famous intro CS course. Updated for 2023 to use Python, then C, then SQL, then web. Lecture videos, problem sets, shorts, and a final project. The full course is on edX, but all the materials and videos are also free on the CS50 site.

The most-used algorithm and data structure interview-prep platform. 3,000+ problems ranging from Easy to Hard, with company-tagged problems (Google, Meta, Amazon, etc.), discussion forums, and 30+ programming languages supported. Free tier: ~600 curated problems and the discussion forum. The 'Blind 75' and 'NeetCode 150' lists are the canonical interview-prep roadmaps.

MIT's IAP course on the 'missing' skills CS programs don't teach: shell, Vim, command-line environment, data wrangling, version control (Git), debugging, profiling, metaprogramming, build systems, cloud, security, the basics of terminals and shells, and how computers actually start up. Lectures, exercises, and hands-on labs.

Undergraduate algorithms course from MIT. Full lecture videos, problem sets, recitation notes, and readings. Covers dynamic programming, graph algorithms, caching, and complexity. The same material Prof. Erik Demaine has taught for two decades.

MIT's graduate algorithms course. Lecture videos, problem sets, and readings cover: divide-and-conquer, dynamic programming, graph algorithms, NP-completeness, approximation algorithms, randomized algorithms, and amortized analysis. The same course as the on-campus MIT 6.046.

MIT's senior-level performance engineering course. Lecture videos and labs covering: C and C++ low-level optimization, multithreaded programming, cache-efficient algorithms, profiling, vectorization, SIMD, GPU computing. Real C/C++ performance engineering — the same material as the on-campus MIT 6.172.

MIT's graduate distributed systems course. Lecture videos, papers, and lab assignments covering: distributed storage (GFS, HDFS, Spanner), consistency models, fault tolerance, Paxos/Raft consensus, distributed transactions, and sharding. The labs implement a fault-tolerant sharded KV store using Raft.

MIT's graduate advanced data structures course. Lecture videos covering: okasaki-style functional data structures, splay trees, red-black trees, persistent data structures, retroactive data structures, geometric data structures (range trees, segment trees, kd-trees), string data structures (suffix trees, suffix arrays, FM-index), and cache-oblivious data structures. Taught by Erik Demaine.

Free, open-source textbook on data structures, available in 7 language editions (Java, C++, Python, pseudocode, C, JavaScript, and Ruby). Covers arrays, linked lists, queues, deques, ordered and unordered lists, trees, hash tables, heaps, integer arrays, strings, and graphs. Written by Pat Morin (Carleton University).

A complete CS education using only free, open-source materials. Maps a 4-year MIT/Harvard/Berkeley-equivalent curriculum to free online courses, textbooks, and problem sets. Used by tens of thousands of self-taught engineers.

Remzi & Andrea Arpaci-Dusseau's free operating systems textbook, used at the University of Wisconsin and 100+ universities worldwide. Covers: virtualization (processes, scheduling, memory), concurrency (locks, threads, condition variables), persistence (file systems, distributed storage, databases). 60+ chapters, free PDF, and free homeworks on GitHub. The right starting point for anyone learning systems programming.

The most-cited curated list of project-based programming tutorials. Each entry is a tutorial that takes you from zero to a complete project. Covers C/C++, C#, Clojure, Dart, Elixir, Go, Haskell, HTML/CSS, Java, JavaScript, Kotlin, Lua, OCaml, PHP, Python, R, Ruby, Rust, Scala, Swift. ~300 tutorials total, all free.

~800 mathematical programming problems, ranked by difficulty. Each problem has a clean mathematical statement and a verifiable answer. Designed to be solved with a few minutes of math and a few lines of code. The canonical platform for math + programming combined practice.

Free interactive learning roadmaps for every developer role: Frontend, Backend, DevOps, Full Stack, React, Angular, Vue, Node.js, Python, Java, Go, Rust, Android, iOS, Machine Learning, Data Engineer, AI Engineer, Game Dev, Cyber Security, UX Design, Product Manager, Blockchain, Computer Science, SQL. Each roadmap shows topics to learn in order, with links to free resources.

Free platform for learning bioinformatics through coding. ~150 problems across DNA, RNA, protein, and population genetics, each paired with a textbook chapter. Problems are real bioinformatics (counting nucleotides, computing DNA strings, finding motifs, alignment, phylogenetics). Used as the practical companion to MIT OCW's 'Biology & Computation' course.

A free, online shell-script linter. Paste your Bash/sh/shell script and it identifies hundreds of common issues: unquoted variables, word splitting, array misuse, portability issues, and style. The linter is the same one shipped in most IDEs. Open source on GitHub (koalaman/shellcheck).

The legendary MIT textbook for intro CS, freely available in HTML and PDF. Teaches the fundamental principles of computer science using Scheme (Lisp dialect). Available from the MIT Press site and on the official mit.edu mirror.

A full open-source full-stack curriculum. Builds 4 substantial projects (a rock-paper-scissors game, a calculator, a weather app, and a full Twitter clone) using HTML, CSS, JavaScript, React, Node, Express, and PostgreSQL. Project-based, no videos to watch — you build.

University of Waterloo's CS 136 — the second intro CS course, taught in Rust. Lecture videos, assignments, and a substantial term project. Covers: algorithms, data structures, memory management, and Rust's ownership/borrowing model. The same course UW CS majors take.

Grant Sanderson's 12-video series building geometric intuition for calculus. The derivative as a limit, the chain rule, the integral as accumulation, Taylor series, all explained with custom animations.

Grant Sanderson's 15-video series that builds geometric intuition for linear algebra: vectors, basis, span, dot products, cross products, change of basis, eigenvalues, and SVD. Uses custom animations to make the math click.

Art of Problem Solving's full free math curriculum: Prealgebra, Algebra 1 & 2, Counting & Probability, Geometry, Intermediate Algebra, Number Theory, Precalculus, Calculus. Self-paced video lessons, problem sets, and the AoPS Wiki (free reference). The paid AoPS classes are the standard training for USAMO and IMO students, but the free content is enough for most learners.

Free math olympiad-style problems and solutions, plus the Alcumus adaptive problem set (free). Covers number theory, algebra, combinatorics, geometry, probability, and calculus at competition-math level. Used by the USAMO and IMO training programs.

Free articles that build geometric intuition for math concepts: e to the i pi, complex numbers, vector calculus, Bayesian probability, dot products, logarithms, the Pythagorean theorem, the chain rule, derivatives, integrals, and many more. Each article is short (5-15 min read) and uses hand-drawn diagrams to make the concept click.

Kalid Azad's free math blog. Articles that build geometric intuition for: e to the i pi, complex numbers, vector calculus, Bayesian probability, dot products, logarithms, the Pythagorean theorem, the chain rule, derivatives, integrals, and many more. Each article is short (5-15 min read) and uses hand-drawn diagrams to make the concept click.

A free, interactive linear algebra textbook with embedded 3D visualizations you can rotate and manipulate. Each chapter covers a concept with an interactive scene. Topics: vectors, basis, span, dot product, linear maps, matrices, change of basis, eigenvectors, and SVD. By the same creators as 3Blue1Brown.

MIT's single-variable calculus course. 35+ lecture videos by David Jerison, recitations, problem sets, and solutions. Covers limits, derivatives, integrals, infinite series, and applications.

Moscow Institute of Physics and Technology's (MIPT) free online courses in Russian with English subtitles. Covers: math (calculus, linear algebra, probability, statistics), physics, computer science, machine learning, and engineering. 50+ courses, all free, all from a top-5 Russian university.

Rice University-published, peer-reviewed open textbook. Covers single-variable and multivariable calculus. Full color, with worked examples, exercises, and an online homework system. Volume 1 (limits, derivatives, definite integrals), Volume 2 (integration techniques, sequences/series, parametric/polar), Volume 3 (vector-valued functions, partial derivatives, multiple integrals, vector calculus).

Full intro statistics textbook covering exploratory data analysis, probability, distributions, hypothesis tests (z, t, chi-square, ANOVA), regression, and statistical literacy. Designed for the AP Statistics course.

Paul Dawkins' comprehensive set of lecture notes and practice problems for algebra, calculus I, II, III, and differential equations. Used by community college and university students as a free supplement to expensive textbooks for 20+ years.

Princeton's algorithms course by Robert Sedgewick (the author of the canonical CLRS-alternative textbook). Lecture videos, programming assignments, and exam problems. Covers: union-find, analysis of algorithms, stacks/queues, sorting, priority queues, symbol tables (BST, red-black), graph algorithms, and string algorithms.

A free online electronics textbook covering DC, AC, semiconductors, op-amps, digital logic, microcontrollers, and communications. Used in intro EE courses as a free alternative to $200 textbooks. Includes a forum and a worksheets section.

The FAA's free aviation maintenance technician handbooks — General, Airframe, and Powerplant. Full-color technical manuals covering everything from sheet metal to turbine engines. Public domain. Same books used to prep for the A&P license exam.

Free intro EE series: circuit analysis, resistors, capacitors, inductors, diodes, transistors, operational amplifiers, logic gates, and feedback. Video lessons with embedded circuit simulators.

A free, multimedia-rich mechanics textbook and tutorial covering statics, dynamics, mechanics of materials, and fluid mechanics. Each concept has video walkthroughs, interactive diagrams, and practice problems. From Penn State University.

MIT's full aerospace engineering course catalog on OCW. ~30 courses covering: aerodynamics (16.100, 16.110, 16.120), propulsion (16.30, 16.50), structures (16.20, 16.215), dynamics and control (16.07, 16.30, 16.31), and aircraft/spacecraft design (16.61, 16.81). 40+ lecture videos per course, full notes, problem sets.

A free public charter school's open course catalog. Full high school and dual-enrollment courses in Engineering, Biomedical Science, Computer Science, Manufacturing, and PLTW tracks. Lesson plans, projects, rubrics, and assessments. Used by other teachers as curriculum.

Two open physics textbooks from Rice: College Physics (algebra-based, for pre-med and life science students) and University Physics (calculus-based, for engineering and physics majors). Full color, with worked examples, conceptual questions, and problems.

OpenStax's growing catalog of free engineering textbooks: Introduction to Electrical Engineering, Introduction to Civil Engineering, Introduction to Mechanical Engineering, Statics and Mechanics of Materials, Thermodynamics, Fluid Mechanics, and more.

Free interactive math and science simulations. 160+ sims covering physics (mechanics, E&M, waves, quantum), chemistry (reactions, states of matter, atomic structure), biology (genetics, natural selection, ecosystem), and math (derivatives, integrals, vectors). Browser-based, no install, available in 60+ languages.

SparkFun's free electronics learning platform. ~80 tutorials on Arduino, basic electronics, soldering, microcontrollers, sensors, motors, and PCB design. Each tutorial includes a parts list, breadboard diagrams, example code (Arduino C++ or CircuitPython), and a working project.

UBC's algorithms course. Lecture videos, slides, and assignments. Covers: divide-and-conquer, dynamic programming, graph algorithms (BFS/DFS/shortest-path/MST), NP-completeness, and a substantial programming component. The right course to take after UBC CPSC 110 (intro CS).

Berkeley's intro EE series. EE 16A covers circuits, linear algebra, and image processing. EE 16B covers circuits, probability, and machine learning. Both have labs (build a touch screen, build a RISC-V processor, build a music recommender). Lecture videos and lab notes free.

Wolfram's free course catalog: Physics, Math, Statistics, Data Science, Machine Learning, AI. Each course uses the Wolfram Language (Mathematica-compatible) for interactive problem sets. Includes certificates of completion. Self-paced.

Georgia State University's free online physics 'textbook' organized as a concept map. Each topic links to related concepts with diagrams and equations. Covers mechanics, heat, sound, electricity, optics, modern physics, and nuclear physics.

Free AP Physics 1, 2, and C curriculum: kinematics, forces, momentum, energy, rotation, gravitation, electricity, magnetism, fluids, thermodynamics, optics, and modern physics. Video lessons with practice exercises.

A free, collaborative online physics library maintained by the UC Davis physics department. Remixes of OpenStax, College Physics, University Physics, and other open textbooks, with additions, corrections, and accessibility improvements.

MIT's brain and behavior course. Lecture videos covering: neurons, synapses, neural circuits, the visual system, motor control, learning, memory, language, emotion, and neurological disorders. Taught by Michale Fee (MIT Brain and Cognitive Sciences). The right intro to neuroscience for engineers and CS people.

MIT's full physics OCW sub-folder. ~50 courses covering classical mechanics (8.01, 8.012), E&M (8.02, 8.022), quantum mechanics (8.04, 8.06, 8.323), statistical mechanics (8.08, 8.13), particle physics (8.701, 8.711), astrophysics (8.901, 8.902), and more. The full undergraduate + graduate physics curriculum.

Full-color college astronomy textbook covering the solar system, stars, galaxies, cosmology, and the Big Bang. Designed for the one-semester intro astro course. Used at universities and for the AP Astronomy exam.

The most rigorous free physics YouTube channel. 500+ videos on cosmology, quantum mechanics, special and general relativity, particle physics, the standard model, the mathematics of physics, and the edge of human understanding. Hosted by astrophysicist Matt O'Dowd.

A free 11-unit intro college physics course covering dark matter, dark energy, quantum mechanics, string theory, biophysics, climate, cosmology, the standard model, fusion, and superconductivity. Each unit has a 30-minute video, an interactive lesson, and a discussion guide. Produced by the Harvard-Smithsonian Center for Astrophysics.

Free biology dictionary, articles, tutorials, and quizzes covering cell biology, genetics, evolution, ecology, anatomy, physiology, biochemistry, and botany. The dictionary has 7,000+ terms. Used as a reference in high school and intro college biology classes.

Free virtual chemistry labs from Carnegie Mellon University. Includes stoichiometry, thermochemistry, equilibrium, acid-base, redox, and spectroscopy. The labs run in the browser — no install. Includes pre-lab and post-lab questions, scenario-based problems, and tutor support.

Hank Green's 46-episode Crash Course Chemistry series, plus 47-episode Biology series. Fast-paced, illustrated, energetic. Each episode is 10-12 minutes and covers one major concept.

Sal Khan's full chemistry and biology curricula: atomic structure, chemical reactions, acids/bases, organic chemistry, the cell, genetics, evolution, ecology, and human body systems. Video + practice exercises.

UC Davis-maintained open biology and chemistry library. Remixed versions of OpenStax and other open textbooks, plus original content. Includes general biology, microbiology, anatomy & physiology, and organic chemistry.

MIT's general chemistry course. 36 lecture videos covering atomic structure, periodic trends, chemical bonding, thermodynamics, kinetics, equilibrium, acid-base chemistry, electrochemistry, and nuclear chemistry.

MIT's intro biology course. 34 lecture videos covering biochemistry, molecular biology, genetics, genomics, cell biology, immunology, and cancer biology. Taught by Eric Lander (the Human Genome Project lead).

MIT's intro psychology course. Lecture videos covering: the brain, perception, learning, memory, cognition, emotion, social psychology, personality, and psychological disorders. Taught by John Gabrieli (MIT Brain and Cognitive Sciences). The OCW version of MIT's intro psych.

Rice's full general biology textbook. The cell, genetics, evolution, biological diversity, plant and animal form/function, and ecology. Used at hundreds of universities and AP Bio programs.

Rice University's full general chemistry textbook. Covers atomic structure, bonding, stoichiometry, thermodynamics, kinetics, equilibrium, acid-base, electrochemistry, organic chemistry, and nuclear chemistry.

University of Helsinki's free intro to AI. ~30 hours of content, exercises with auto-grading, and a free certificate of completion. Two parts: 'Introduction to AI' (no math, no coding — for everyone) and 'Building AI' (Python exercises for the basics of building AI). Translated into 20+ languages.

A list of 500+ AI/ML/DL/CV/NLP projects with code, organized by category. Each entry links to a GitHub repo with a working implementation. Categories: Computer Vision, NLP, Deep Learning, ML, GANs, Reinforcement Learning, Speech, Time Series, Recommendation Systems. Real projects, not tutorials.

Implementation of 17+ agentic AI architectures. Each has a working notebook: ReAct, Reflexion, Plan-and-Execute, BabyAGI, AutoGPT, multi-agent, hierarchical, supervisor, swarm, human-in-the-loop, and more. Built with LangGraph and OpenAI.

Andrej Karpathy's video lecture series that builds neural networks from scratch, in code, step by step. 8 lectures covering micrograd, makemore (backprop), GPT, building a tokenizer, character-level language modeling, and attention/transformers. Each lecture is 2+ hours and ends with a working implementation. The most-watched deep learning series of 2023-2025.

A curated, hand-picked collection of the most useful AI/ML knowledge repositories on GitHub. Organized into: Library (awesome-machine-learning, best-of-ml-python, awesome-python), Papers, ML Frameworks, Computer Vision, NLP, Reinforcement Learning, Generative AI, MLOps, AI Ethics, Quantum ML. Each repo has a short description, star count, and quality assessment.

A weekly curated list of the most interesting ML papers, organized by topic. ~200 papers covering: LLMs, diffusion models, RAG, agents, RL, computer vision, NLP, multimodal, and AI safety. Each entry has a one-line summary and a link to the paper. The right TL;DR for what's actually interesting in ML research.

DAIR.AI's full open-source guide to prompt engineering. ~15k+ stars. Covers: prompting techniques (zero-shot, few-shot, CoT, ReAct, ToT, self-consistency, RAG, PAL), prompt injection, defenses, applications, and per-task recipes. Updated monthly with new research. 25+ notebooks in Python.

The MIT Press 'Deep Learning' textbook by Yoshua Bengio, Ian Goodfellow, and Aaron Courville. The free HTML edition is the same as the printed book. Covers: applied math, machine learning basics, deep feedforward networks, regularization, optimization, convolutional networks, recurrent networks, linear factors, autoencoders, representation learning, structured probabilistic models, Monte Carlo methods, and more.

A curated list of the most-used tools and resources for production ML. Covers: MLOps, model serving, model monitoring, feature stores, model registries, data validation, distributed training, and explainability. Each entry has a short description and category tags.

A free service that ranks GitHub users, organizations, and repositories by topic and language. 100+ languages and topics. Updated daily. The right tool for finding the most-followed developers, the most-starred repos, or the most-active organizations in any language or field.

A curated list of free AI courses from universities, platforms, and individual instructors. Categories: AI foundations, ML, DL, NLP, Computer Vision, MLOps, Generative AI, and AI tools. Each course has the platform, the URL, and a short description. 50+ courses, all 100% free.

Google's free intro ML course: ~15 hours of lectures, real-world case studies (the same ones Google uses internally), 25+ interactive exercises with TensorFlow, and a final project. Includes sections on responsible AI and fairness.

Practice implementing classical ML algorithms from scratch in Python (no scikit-learn). Jupyter notebooks covering regression (linear, polynomial, logistic), classification (KNN, decision trees, SVM, Naive Bayes), clustering (K-Means, DBSCAN, Hierarchical), and neural networks. Each notebook has visualizations and math explanations. ~30 algorithms total.

The free Hugging Face course on transformers and NLP. ~12 chapters covering how transformers work, how to use the Hugging Face Transformers library, fine-tuning, building datasets, training models, and deploying. Each chapter is a free Colab notebook.

A curated list of resources for ML interpretability (XAI). Covers: SHAP, LIME, partial dependence, accumulated local effects, model-agnostic methods, and interpretable models. Each entry has a short description and a 'why use this' note. Authored by a long-time practitioner (Patrick Hall).

Free applied ML course: 'How to Design, Train, and Deploy ML Products End-to-End'. Covers the full lifecycle: problem framing, data engineering, training, evaluation, deployment, monitoring. Code-first with Python, PyTorch, and Ray. ~50 lessons.

A free, opinionated article on what math you actually need for ML. Covers: linear algebra (vectors, matrices, eigenvalues), probability (Bayes, distributions, expectations), calculus (multivariable, gradients, chain rule), and optimization (gradient descent, Lagrange multipliers). With specific course/resource recommendations per topic.

Microsoft's free 12-lesson course on building AI agents. Covers the agentic loop, function calling, tool use, RAG, planning, multi-agent systems, deployment, observability, and agent evaluation. Each lesson has a Python notebook, a video, and a written walkthrough. Uses Azure OpenAI but works with any OpenAI-compatible API.

Microsoft's free 12-week, 24-lesson AI curriculum. Covers symbolic AI, neural networks, computer vision, NLP, GANs, reinforcement learning, and AI ethics. Each lesson has a written intro, a video, a notebook, and hands-on exercises. ~50 hours of content. The right starting point for absolute beginners to AI.

Microsoft's free 10-week, 20-lesson data science curriculum. Each lesson has a written walkthrough, a video, sketchnotes, quizzes, and a project. Covers: intro to DS, data collection, data prep, data visualization, data science in the cloud, data science ethics, real-world case studies. No install — runs in the browser.

Jeremy Howard's 7-week deep learning course. Top-down (build things first, then understand why they work). Uses PyTorch. Builds a state-of-the-art image classifier, a text classifier, a recommendation system, and a neural net from scratch. The course site has free videos, interactive notebooks, and a book.

The most comprehensive free guide to prompt engineering. Covers prompting techniques (zero-shot, few-shot, chain-of-thought, ReAct, tree-of-thoughts), prompt injection, defenses, applications (coding, reasoning, generation, extraction), tools, and LLM basics. Updated monthly with new techniques.

A free, code-first RAG tutorial that builds RAG from scratch using LangChain. 14 videos + notebooks covering indexing, retrieval, generation, query transformation, routing, query construction, indexing pipeline, retrieval pipeline, generation, and end-to-end RAG. By LangChain's co-founder Harrison Chase.

Sebastian Raschka's free online book + GitHub repo. Walks through implementing a GPT-like LLM from scratch in PyTorch. Covers: text data prep, tokenization, attention, the transformer block, training, fine-tuning, RLHF, and deployment. The most thorough free resource for understanding LLM internals in 2025.

Stanford's flagship AI course, free YouTube lectures and full materials. Covers: search, constraint satisfaction, Markov decision processes, reinforcement learning, machine learning, deep learning, natural language processing, robotics, vision. Recorded lectures (2021 and 2024), slides, code, readings, and homeworks. Same course Stanford CS students take.

Stanford's flagship machine learning course, free YouTube recordings from 2018, 2019, and 2022. Taught by Andrew Ng. Covers: supervised learning (linear regression, logistic regression, neural networks, SVMs, decision trees), unsupervised learning (k-means, PCA, ICA), reinforcement learning, ML best practices, applied ML. The same course that became Andrew Ng's Coursera intro ML course.

Josh Starmer's YouTube channel that explains statistics and machine learning with hand-drawn diagrams and step-by-step walkthroughs. 250+ videos covering linear regression, logistic regression, gradient boosting, random forests, neural nets, RNNs, transformers, and more.

The famous Stanford textbook on statistical learning, free PDF from the authors. Covers linear and polynomial regression, logistic regression, splines, GAMs, trees, random forests, boosting, SVMs, neural nets, and unsupervised learning. The math is dense but the writing is clear.

A massive curated collection of resources for system administrators, security engineers, and devops. ~100 categories: bash, networking, TLS, linux, performance, monitoring, security, programming, sysadmin, data-science. Each entry has a short description and a link. The most-comprehensive sysadmin reference on the web.

Free online cybersecurity training platform. Courses on security+, network+, CEH, CISSP, cloud security, SOC analyst, penetration testing, incident response, and more. Some include free certificates of completion.

Free cybersecurity tutorials from the SANS Institute. Three modules: Operating Systems, Networking, and System Administration. Each module is video + practice, and you get a free SANS certificate on completion.

Free interactive cryptography challenges. 100+ problems covering XOR, RSA, elliptic curves, AES, hash collisions, and modern protocols. Each challenge has a clear mathematical statement and a Python-friendly API. The natural progression from CryptoPals once you've finished the 8 sets.

Free hands-on cryptography challenges. 8 sets of progressively harder problems: break ECB, break CBC, implement RSA, break RSA, break DSA, implement SHA-1, and more. Each problem teaches a real attack and a real defense.

The free calendar for Capture The Flag (CTF) cybersecurity competitions worldwide. 100+ events per year, ranked by difficulty and team. Each event has writeups from participants. The right starting point for anyone who wants to compete in CTFs and find local teams.

Free cybersecurity learning modules on Hack The Box. The free tier includes the 'Starting Point' path, ~20 modules covering Linux fundamentals, networking basics, web attacks (SQLi, XSS, SSRF), file inclusion, and Windows privilege escalation. Paid paths add more advanced content.

500+ free cybersecurity videos: CTF walkthroughs, malware analysis, reverse engineering, bug bounty writeups, career advice, and the popular 'Hacking 101' series. John Hammond is a former NSA cybersecurity analyst and the most-watched cybersecurity YouTuber.

MIT's grad-level security course. Lecture videos and problem sets covering buffer overflows, syscall sandboxing, web app security (XSS, SQL injection, CSRF), network security (TLS, BGP, DNS attacks), mobile security, and side-channel attacks.

NetworkChuck's free cybersecurity, networking, and IT career YouTube channel. 1,000+ videos on Linux, networking, ethical hacking, AWS, Azure, CCNA, and the CompTIA certs. Most-watched free IT career channel. Beginner-friendly with hands-on labs (each video has a related free lab or sandbox).

Free war-game servers with shell access. Each wargame is a series of progressively harder levels: Bandit (linux shell), Natas (web), Narnia (binary exploitation), Krypton (cryptography), Leviathan (problem-solving), Maze (mazes), and more. SSH into a remote server to play.

The OWASP Foundation's free, open-source methodology for testing web application security. Covers information gathering, configuration, identity management, authentication, authorization, input validation, error handling, cryptography, business logic, and client-side testing.

A free, beginner-friendly CTF for high school and college students, run by CMU's security institute. 100+ challenges across: web exploitation, reverse engineering, cryptography, binary exploitation, forensics, and general skills. The yearly event is in March, but the platform stays open year-round for practice.

A free, hands-on platform for learning modern pwn (binary exploitation) skills. ~12 modules covering: assembly, shellcode, format strings, return-oriented programming, heap exploitation, kernel exploitation. Each module has interactive problems with auto-grading. The successor to the pwnable.kr/pwnable.tw model with a modern interface.

A free cybersecurity learning platform with guided paths for: complete beginners (Pre-Security, Introduction to Cyber Security), web fundamentals, networking, Linux, scripting, web application pentesting, network pentesting, red teaming, and SOC Level 1. Each path has hands-on labs in a browser. Paid tier for advanced content.

freeCodeCamp's front-end libraries cert. Covers Bootstrap, jQuery, Sass, React, and Redux. ~300 interactive challenges + 5 projects including a Markdown previewer, a drum machine, a calculator, a Pomodoro clock, and a 25+5 clock.

A List Apart — the long-running web design publication founded 1998. ~2,000 articles on web standards, accessibility, CSS, typography, design systems, UX, and content strategy. Authors include Jeffrey Zeldman, Ethan Marcotte (Responsive Web Design), and Eric Meyer (CSS). The right reference for the craft of web design.

A community-driven free resource for web accessibility. Includes an accessibility checklist, articles, patterns, ARIA examples, and how-to guides. Covers WCAG 2.2, screen reader testing, keyboard navigation, color contrast, semantic HTML, and accessible forms.

Canva's free design school. ~50 tutorials on graphic design, branding, typography, photography, color, and social media design. Each tutorial is short (10-20 minutes) with examples and a 'try it' exercise. The right starting point for non-designers.

Harvard's CS50 follow-on course. Builds a social network (a Twitter clone) in Python, Flask, JavaScript, SQL, and React. Lecture videos, problem sets, and a final project. Updated for 2020 to use modern React.

A free, open-source checklist for shipping production-ready websites. Covers: HTML (head, valid tags, attributes), Webfonts, SEO, accessibility, performance, security (CSP, HSTS, XSS), and more. Each item links to a 'how to fix' article. The standard pre-launch checklist.

A free, modern JavaScript tutorial from fundamentals to advanced. 4 parts: language fundamentals, browser: Document, Object Model Events, articles on advanced topics. Used by working engineers as a reference for ES2015+ features.

A free site that documents 20+ UX design principles with examples: Fitts's Law, Hick's Law, Jakob's Law, Miller's Law, the Aesthetic-Usability Effect, and more. Each principle has a one-paragraph description, an example, and a citation. The right quick-reference for any UI decision.

Adam Wathan and Steve Schoger's 'Refactoring UI' book — most of the core content is freely available as blog posts on the site. The book teaches practical UI design: hierarchy, contrast, layout, color, typography, and the actual techniques for improving your UI's design quality. The fastest way to learn UI design as a developer.

Free in-depth articles on web design, frontend, UX, accessibility, performance, and the business of web. ~50 new articles per month, all free. The standard reading for working web designers and developers. Authors include Rachel Andrew, Lea Verou, Vitaly Friedman (founder), and the wider web community.

The Odin Project's Ruby/Rails full-stack path. Builds 5 substantial projects (a Tic Tac Toe, a chess game, a custom forms clone, a Facebook clone, a Reddit clone) using HTML, CSS, JavaScript, Ruby, Rails, and PostgreSQL. Same project-based approach as the JS path.

Microsoft's official TypeScript documentation. The 'Handbook' section is a free full-book tutorial: basic types, interfaces, classes, generics, advanced types, modules, and the integration patterns (TS + React, TS + Node, TS + Express). Updated with every TypeScript release.

The W3C's free, official guide to building accessible web components. Patterns for: dialogs, menus, tabs, accordions, autocomplete, breadcrumbs, carousels, data grids, disclosure widgets, navigation, sliders, and tabs. Each pattern has working code, accessibility requirements, and a11y test procedures.

A free visual skill map for web development. 100+ web skills organized into topics: HTML, CSS, JavaScript, Accessibility, Frameworks, Build Tools, Performance, Web APIs, and more. Each skill is a node in a clickable mind map. Click any skill to see its description and resources.

Google's free web development learning platform. Courses on CSS, HTML, JavaScript, accessibility, performance, responsive design, and modern web platform features. Each course is hands-on with code playgrounds.

Google's free web platform learning site. Courses on CSS, HTML, JavaScript, accessibility, performance, responsive design, PWA, and the modern web platform. Taught by the Chrome DevTools and Lighthouse teams. Hands-on code playgrounds for every lesson.

A curated list of free and open resources for robotics: courses, books, papers, datasets, simulators (Gazebo, PyBullet, Webots, MuJoCo), and the major open-source robotics frameworks (ROS, ROS2, MoveIt). Covers all major robotics subfields: SLAM, manipulation, locomotion, perception, control, planning, and swarm.

Harvard's game dev course. Uses Unity and LÖVE 2D to build 8 games (Pong, Flappy Bird, Helicopter, Match-3, Angry Birds, Portal 2D, The Legend of Zelda). Lecture videos and tutorial notes for each game.

Free coding practice specifically for mobile languages: Swift (iOS), Kotlin (Android), and Dart (Flutter). 100+ exercises per track with mentor feedback. Covers SwiftUI and Jetpack Compose through hands-on coding.

The complete Godot game engine documentation plus the 'Get Started' tutorial series. Covers 2D, 3D, scripting in GDScript, exporting to all platforms. Includes official sample projects (Dodge the Creeps, Memory Game, Platformer).

A free, community-built cookbook of recipes for the Godot 4 game engine. ~100 recipes covering: movement, physics, UI, networking, shaders, AI, and procedural generation. Each recipe has a working Godot project. The right companion to the official Godot docs.

MIT's free visual programming environment for building Android and iOS apps. Drag-and-drop blocks (similar to Scratch) that generate real Kotlin/Swift code. Includes tutorials for building a chat app, a game, and a location-aware app.

A free repository of game art — 2D sprites, 3D models, sound effects, music, and textures. All CC-licensed. Browse by category (characters, environments, items, UI, etc.) and license (CC0, CC-BY, CC-BY-SA). The right starting point for any indie game with no art budget.

Apple's official Swift learning resources: Swift documentation, A Swift Tour (interactive playground), and the Swift Book (The Swift Programming Language, free on the site). For iOS/macOS development.

Unity's free learning platform. 100s of hours of free courses on 2D, 3D, mobile, VR, and multiplayer. Includes the official Unity Essentials pathway (5+ hours of intro content) plus specialized courses for FPS games, RPGs, and platformers.

Epic Games' free Unreal Engine learning platform. Tutorials for first-time developers, level design, blueprints (visual scripting), C++ programming, lighting, materials, and cinematics. Includes sample projects and starter templates.

The Open University UK's free course platform. ~1,000 free courses across: business, education, health, history, languages, law, math, science, social science, technology. Each course has 8-10 hours of content with quizzes and a free 'Statement of Participation' certificate. The right free source for Open University-quality courses.

Saylor Academy's free business courses: Accounting, Business Law, Economics, Finance, Marketing, Management, Operations, Statistics. ~140 courses total, each with final exam and free certificate. Self-paced. The courses are also accepted for credit at 100+ colleges.

BCcampus's free open-textbook collection, filtered for business and economics. 100+ textbooks including Intro to Business, Principles of Financial Accounting, Intro to Marketing, Business Communication, Entrepreneurship, Organizational Behavior. All Creative Commons licensed.

Sal Khan's free econ/finance curriculum: microeconomics, macroeconomics, finance, capital markets, personal finance, taxes, and current economics. Video lessons with practice exercises.

Khan Academy's free entrepreneurship curriculum. Covers the basics of starting a business, market analysis, marketing, operations, finance, and growth. Video lessons with case studies of real companies.

The University of Minnesota's free open-textbook library. 60+ business and economics textbooks reviewed by the Open Education Network, all peer-reviewed and free to use. Includes Principles of Accounting, Principles of Marketing, Managerial Economics, Corporate Finance, Entrepreneurship, Operations Management.

Rice's full accounting textbook. The accounting cycle, financial statements, assets, liabilities, equity, revenue recognition, and financial statement analysis. The 2e edition includes video walkthroughs.

Rice's full economics textbook (micro + macro). Demand, supply, market equilibrium, elasticity, consumer/producer theory, market structures, GDP, inflation, unemployment, monetary/fiscal policy, and international trade.

Rice's full marketing textbook. The marketing mix (4 P's), consumer behavior, market research, segmentation, targeting, positioning, branding, integrated marketing communications, and digital marketing. Used at universities and for marketing certification prep.

A pan-European MOOC aggregator from the European Commission's Open Education initiative. ~400+ free courses from European universities. Covers all major subjects. Most courses are translated into 4-6 languages. The right starting point if you want a European perspective on any subject.

The BBC's free school subject platform covering the full UK National Curriculum from primary to GCSE. Subjects: math, English, science, history, geography, languages, computing, art, music, PE, citizenship. Interactive lessons, videos, quizzes, and practice questions. The right starting point for any UK school subject.

The BBC's free educational video platform. ~5,000 short videos on history, science, English, math, geography, and the arts. 5-15 minutes each. The right BBC documentary-style intro to any school subject.

The original non-profit digital library, founded 1996. 44+ million free texts including books, academic articles, government documents, audio recordings (78+ million), videos, software, and web pages. The Open Library (openlibrary.org) is its lending library arm — borrow modern ebooks with a free account.

Internet Archive's modern ebook lending library. Borrow 1-2 million modern ebooks for 14 days with a free account. Catalog of 30+ million books (most with metadata, many with full text). The closest thing to a free public library for digital books. Founded 2006.

A free, peer-reviewed open-access journal publisher in the humanities. Diamond open-access — no fees for readers, no fees for authors. 30+ journals covering classics, film, philosophy, history, medieval studies, postcolonial writing, and more.

Keith Wrightson's course on English history from the late 15th to the early 18th century. 25 lecture videos on the Tudors, the English Civil War, the Glorious Revolution, the rise of parliament, and the social/economic history of early modern England.

Steven Smith's political philosophy course. 24 lecture videos on Plato, Aristotle, Augustine, Aquinas, Machiavelli, Hobbes, Locke, Rousseau, Burke, Mill, Marx, and Nietzsche. The same course taught at Yale.

Rice's intro philosophy textbook. Covers the major problems (mind, knowledge, free will, ethics, political philosophy, philosophy of religion, existentialism) and the major figures (Plato, Aristotle, Descartes, Hume, Kant, Nietzsche, Sartre).

Rice's full U.S. history textbook. Pre-Columbian America through the present, with extensive primary source coverage of the founding, the Civil War, Reconstruction, the Gilded Age, the World Wars, the civil rights era, and modern America.

A free, open-source library of beautifully typeset, carefully edited public-domain ebooks. Pride and Prejudice in 3 different editions, the Sherlock Holmes canon, the complete Shakespeare, Dickens, Twain, Tolstoy, and more. Each book is hand-typeset with attention to typography, with a generated cover, and free of publisher ads.

A free mirror of academic and public-domain books and papers. ~43 million books and ~98 million papers indexed. Aggregates content from Library Genesis, Z-Library mirrors, Sci-Hub mirrors, and Internet Archive. Faster, cleaner UI than the older mirrors.

Wikimedia's free open-content textbook library. 35,000+ free textbooks in 80+ languages. Subjects span humanities, sciences, mathematics, technology, languages, cooking, and the arts. Each book is collaborative and editable. Many are used in real schools and universities.

Wikimedia's free library of source texts. Public-domain books, periodicals, letters, speeches, constitutions, treaties, and historical documents. Every text is transcribed and proofread by volunteers. 5+ million works in English; 50+ languages total. Sister project of Wikipedia.

Wikimedia's free learning resource. 50,000+ learning resources, lesson plans, study guides, and course materials in every major academic field. Sister project of Wikipedia. Run by the Wikimedia Foundation, peer-reviewed by educators.

Open-source flashcard app that uses spaced repetition (the SM-2 algorithm) to make memorization 3-5x more efficient than traditional study. Available on Mac, Windows, Linux, iOS (paid, $25 one-time), Android (free), and a free web version. ~14,000 free community-created decks for languages, MCAT, USMLE, geography, etc.

Open-source flashcard app that uses spaced repetition (the SM-2 algorithm) to make memorization 3-5x more efficient than traditional study. Available on Mac, Windows, Linux, iOS (paid, $25 one-time), Android (free), and a free web version. ~14,000 free community-created decks for languages, MCAT, USMLE, geography, etc.

The BBC's free language learning site. Full courses for French, German, Italian, Spanish, and more. Each course has video, audio, cultural notes, and structured lessons. Includes the famous 'A Day in the Life' immersion videos.

Free gamified language learning app. 40+ languages including Spanish, French, German, Italian, Portuguese, Japanese, Chinese, Korean, Russian, Arabic, Hindi, and 30+ more. 5-10 minute daily lessons, streak tracking, leaderboards. Optional paid Plus tier (not required to learn the language).

Duolingo — the most-used free language learning app. 40+ languages with 5-10 minute daily lessons, streak tracking, leaderboards, and audio. The free tier teaches the full language; the Plus tier adds hearts, no ads, and offline mode. The right starting point for any new language.

The largest pronunciation guide in the world. 6+ million words pronounced by native speakers in 400+ languages. Each word has multiple pronunciations (regional accents, male/female). Free tier has unlimited searches.

Free public-domain language courses from the U.S. Foreign Service Institute. Originally developed to train American diplomats. Courses for ~50 languages including Arabic, Mandarin, Russian, French, Spanish, German, Japanese, Korean, and many more rarely-covered languages (Hausa, Uzbek, Sinhala). Each course is 100+ hours of audio + text.

italki — a platform to book affordable 1-on-1 language tutors. Tutors from $5-15/hr set their own rates. Free trial with most tutors. ~150 languages. The right complement to any self-study app — the conversation practice is what makes you fluent.

Loecsen — a free phrase book for 50+ languages. Each language has ~300 essential phrases organized by situation (greetings, transport, accommodation, etc.) with audio of native speakers. The right starting point for a quick trip or a basic conversation.

Mango Languages — a high-quality language learning platform with 70+ languages, free with a public library card (most US public libraries offer it). Real conversations, cultural notes, and a film-based learning approach (each lesson is built around a short film). More serious than Duolingo, less academic than FSI.

Memrise — a free language learning app focused on vocabulary and phrases. Uses video clips of native speakers saying the words in real contexts. ~20 languages. Free tier covers the basic courses; paid Plus tier unlocks more content.

MIT's free foreign language courses: Chinese, French, German, Japanese, Spanish. Lecture videos, audio, and structured lessons at the college level. The Chinese and Japanese courses are particularly comprehensive (3 semesters each).

Curated index of 200+ free language lessons from universities and language schools. Arabic, Chinese, French, German, Hebrew, Italian, Japanese, Korean, Portuguese, Russian, Spanish, and more. Mix of audio, video, and text lessons.

A free browser-based chiptune / synthwave music composer. Build songs by drawing notes on a piano roll; choose from 9 instruments and 4 effect modes; export as WAV, MP3, or shareable link. No account, no install.

Free online music school. Video lessons on music theory, ear training, and composition. Covers intervals, scales, chords, modes, and basic composition. Free and self-paced.

Good UI — a free archive of UI/UX articles and examples. ~30 articles on the most common UI mistakes and how to fix them: button placement, form design, error messages, navigation patterns. The right quick-reference when you're reviewing any UI.

Justin Sandercoe's free guitar lessons. 1,500+ video lessons covering beginner to advanced. Acoustic, electric, blues, rock, jazz, fingerstyle. Structured into 9 grades (Beginner through Advanced).

Sal Khan's free art history curriculum. Covers prehistoric art, ancient Egypt, ancient Greece, ancient Rome, Byzantine, Islamic, Medieval, Renaissance, Baroque, Romanticism, Impressionism, Modernism, and global art traditions. Video lessons with high-resolution images.

Sal Khan's free art history curriculum. Covers prehistoric art, ancient Egypt, ancient Greece, ancient Rome, Byzantine, Islamic, Medieval, Renaissance, Baroque, Romanticism, Impressionism, Modernism, and global art traditions. Video lessons with high-resolution images and quizzes.

Rice's intro art appreciation textbook. Covers art fundamentals (line, shape, color, form, texture, space, composition), the major periods (Prehistoric through Contemporary), and global art traditions. Includes high-res images and discussion questions.

Rice's intro music textbook. Covers music fundamentals (rhythm, melody, harmony, form), the major periods (Medieval, Renaissance, Baroque, Classical, Romantic, Modern), and global music traditions. Includes audio examples.

A free site that documents 25+ design principles with examples: alignment, contrast, hierarchy, repetition, proximity, balance, white space, color, and more. Each principle has a one-paragraph description, an example, and a citation. The right quick-reference for any design decision.

Saylor's free personal development, sociology, and psychology courses. Includes Intro to Sociology, Intro to Psychology, Developmental Psychology, Abnormal Psychology, Social Psychology, Lifespan Development, and Health Psychology. Each with final exam and free certificate, college-credit eligible at 100+ schools.

Wolfram's free course catalog with a dedicated certifications section. Courses: Physics, Math, Statistics, Data Science, Machine Learning, AI. Each course uses the Wolfram Language (Mathematica-compatible) for interactive problem sets. Free certificates of completion. Self-paced. The certifications page is the most useful entry point for proving skill.

Grant Sanderson's free YouTube channel. 150+ videos on math (Essence of Calculus, Essence of Linear Algebra, The Laplace Transform, Differential Equations, the Mandelbrot set) and AI (Neural Networks, Backpropagation, Transformers, GPT, How LLMs work, Attention). Custom animations make abstract math feel intuitive. 5M+ subscribers.

Encyclopaedia Britannica — the 200-year-old encyclopedia, now free with attribution. ~120,000 articles reviewed by experts. The right quick-reference for any general knowledge topic. Higher quality than Wikipedia for academic and historical topics.

A free, browser-based tool that parses any shell command and explains each part. Write `find . -name '*.py' -mtime -7` and explainshell breaks down the find command, each flag, and each argument. Uses Python, parses POSIX and Bash. Open source on GitHub.

Fireship's 100-second explainer videos for every major tech topic. 500+ videos covering JavaScript, Python, Go, Rust, React, Vue, Docker, Kubernetes, Git, Linux, AWS, and 50+ other topics. Each video is 2-10 minutes and ends with a meme. The right channel for 'I need to understand X in 5 minutes'.

The U.S. Securities and Exchange Commission's free investor education site. Free courses and tools on saving, investing, mutual funds, ETFs, retirement accounts, financial advisors, and avoiding fraud. Includes a free 'Save and Invest' educational program.

Sal Khan's free educational platform covering math, science, computing, economics, finance, art history, grammar, SAT prep, MCAT prep, and more. 5,000+ videos, 100,000+ practice exercises. Personalized learning dashboard. Free for everyone, no paywalls on any content.

Khan Academy's intro psychology curriculum. Covers the brain, sensation, perception, learning, memory, cognition, emotion, social psychology, personality, and psychological disorders. Video lessons + practice.

Sal Khan's free life skills curriculum. College admissions, career planning, personal finance, mental health, and citizenship. Video lessons with practice exercises.

Khan Academy's free personal finance curriculum. Covers banking, credit, taxes, investing (stocks, bonds, mutual funds, retirement accounts), insurance, and buying a home. Video lessons + practice exercises.

The Library of Congress's free digital collections. ~20 million items — books, photographs, manuscripts, audio recordings, films, maps, and sheet music. All public domain. Search by topic, format, or date. The right starting point for any primary source research.

A free K-12 open-course catalog covering high school subjects: English, math (algebra through calculus), science (biology, chemistry, physics), social studies, languages, arts, and AP courses. Each course has lesson plans, videos, readings, and assessments. Built by Mountain Heights Academy, a public charter school.

Rice's intro education textbook. Covers the history of education, philosophy of education, curriculum, instruction, classroom management, assessment, and the sociology of education. Used at hundreds of universities and for teacher certification prep.

Rice's full intro sociology textbook. Covers culture, socialization, deviance, crime, stratification, race, gender, sexuality, religion, education, government, and social change. Used at hundreds of universities and for AP Sociology.

Rice's full intro sociology textbook. Covers culture, socialization, deviance, crime, stratification, race, gender, sexuality, religion, education, government, and social change. Used at hundreds of universities.

Free online courses with free digital certificates. 4,000+ courses in health, business, IT, language, and trades. Categories include plumbing, carpentry, electrical, automotive, construction, and HVAC. Each course has a free digital certificate (paid printed certificate available).

The U.S. Occupational Safety and Health Administration's free training resources. Industry-specific safety courses (construction, general industry, maritime), hazard communication (HazCom), confined space entry, lockout/tagout, fall protection, and more. Certificates of completion for many courses.

OSHA's free Outreach Training Program — 10-hour and 30-hour courses in general industry, construction, and maritime. Free if you complete it through a local community college or authorized trainer (most are free; the program itself is fully funded by OSHA).

AC Service Tech (by Sam Myers) is the second-best free HVAC training YouTube channel. 500+ videos focused on residential air conditioning troubleshooting, electrical, and refrigeration. New videos every week. Most are 10-25 minutes long and solve one specific problem.

Jody Collier's free welding tutorial channel. 100s of videos on stick, MIG, TIG, oxyacetylene welding, and weld inspection. Real welding, real mistakes, real fixes. Industry-experienced welder, not a hobbyist.

HVAC School (by Bryan Orr) is the most-respected free HVAC training YouTube channel. 1,000+ videos on refrigeration, electrical, air conditioning, and heat pump troubleshooting. Industry-experienced technicians, not influencers. Includes free podcast and free HVAC-R training newsletter.

HVAC School (by Bryan Orr) and AC Service Tech are the two best free HVAC training YouTube channels. 100s of videos on refrigeration, electrical, air conditioning, and heat pump troubleshooting. Industry-experienced technicians, not influencers.

Khan Academy's AP Macroeconomics prep: GDP, inflation, unemployment, money, banking, monetary policy, fiscal policy, international trade, exchange rates, and economic growth. Practice problems modeled on the AP exam.

The U.S. Department of Labor-funded free OER (Open Educational Resources) library for workforce development. ~800 free courses, simulations, and tools for skilled trades, manufacturing, healthcare, IT, and customer service. Built with the same authoring tools that produced the most-used online college courses.

The U.S. Department of Labor-funded free OER (Open Educational Resources) library for workforce development. ~800 free courses, simulations, and tools for skilled trades, manufacturing, healthcare, IT, and customer service. Built with the same authoring tools that produced the most-used online college courses.

SparkFun's free electronics learning platform. Tutorials on Arduino, basic electronics, soldering, microcontrollers, sensors, motors, and PCB design. Each tutorial includes a parts list, breadboard diagrams, example code (Arduino C++ or CircuitPython), and a working project. ~80 tutorials total.

Jody Collier's free welding tutorial channel. 1,000+ videos on stick, MIG, TIG, oxyacetylene welding, and weld inspection. Real welding, real mistakes, real fixes. Industry-experienced welder, not a hobbyist. Includes the famous 'MIG welding settings chart' (most-viewed welding video on YouTube).

WeldingWeb's free YouTube channel — 500+ videos on stick, MIG, TIG, oxyacetylene, and pipe welding. Real shop footage, real weld tests, industry tips. The right channel for working welders wanting to improve specific techniques (not a beginner's channel).

The free open-access archive of scholarly articles in physics, mathematics, computer science, quantitative biology, quantitative finance, statistics, electrical engineering, systems science, and economics. 2+ million papers. Pre-prints (not yet peer-reviewed in some fields), but the standard venue for sharing research.

The free open-access archive of scholarly articles in physics, mathematics, computer science, quantitative biology, quantitative finance, statistics, electrical engineering, systems science, and economics. 2+ million papers. Pre-prints (not yet peer-reviewed in some fields), but the standard venue for sharing research.

A curated list of 1,000+ free AI tools, frameworks, datasets, and APIs across 30+ categories: NLP, computer vision, generative AI, MLOps, AI agents, vector databases, prompt engineering, and more. Each entry has a short description, link, and tags.

A curated list of free data science resources. Categories: free courses, tutorials, books, MOOCs, videos, podcasts, datasets, journals, blogs, competitions, conferences, and tools. Covers Python, R, Julia, SQL. Each entry has a short description and link. The most-comprehensive free DS resource list.

A free index of ~20,000 peer-reviewed open-access journals across all disciplines. Every journal listed is fully open-access (no paywalls) and vetted for quality. Searchable by topic, language, and country.

Google's free academic search engine. Searches across all disciplines for peer-reviewed papers, theses, books, abstracts, and court opinions. Links to free full-text versions when available (e.g. via the 'All versions' link).

Google's free academic search engine. Searches across all disciplines for peer-reviewed papers, theses, books, abstracts, and court opinions. Links to free full-text versions when available (e.g. via the 'All versions' link).

A free, open catalog of 200+ million scholarly works and authors. Successor to Microsoft Academic Graph. Free API, no rate limits, no paywalls. Includes papers, authors, institutions, journals, and concepts.

The Public Library of Science's flagship open-access journal. 200,000+ peer-reviewed research articles across science and medicine. Every paper is open-access, no subscription required, no paywalls.

The Public Library of Science's flagship open-access journal. 200,000+ peer-reviewed research articles across science and medicine. Every paper is open-access, no subscription required, no paywalls.

The U.S. National Library of Medicine's free full-text archive of biomedical and life-sciences journal literature. ~7 million full-text articles. Searchable by topic, author, and journal. PubMed (the search engine) is also free at pubmed.ncbi.nlm.nih.gov.

The U.S. National Library of Medicine's free full-text archive of biomedical and life-sciences journal literature. ~7 million full-text articles. Searchable by topic, author, and journal. PubMed (the search engine) is also free at pubmed.ncbi.nlm.nih.gov.

The Allen Institute for AI's free AI-powered academic search engine. 200+ million papers across all disciplines. Uses machine learning to identify the most relevant papers, the most influential citations, and the most important authors. Includes a free API for research.