59 websites to learn something new

Explainers that make hard ideas obvious. Every learn site in the directory, each one checked by a person.

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Ba Ba Dum

Learn everyday words in 21 languages through five quick picture games, with bold illustrations and native audio.
- Learn
- Free
- babadum.com
Car Anatomy

An interactive 3D car you can take apart: engine, gearbox, brakes and suspension, each explained in plain English as it moves.
- Learn
- Free
- underthehood.online
Chemical Equations Online

Type the reactants and it predicts the products and balances the equation, with the steps shown.
- Learn
- Free
- chemequations.com
DOF Simulator

Pick a camera, lens, aperture and distance and watch the depth of field and background blur change on a sample photo.
- Learn
- Free
- dofsimulator.net
Entertrained

Practise typing by retyping classic novels page by page, so your speed drills double as reading time.
- Learn
- Free
- entertrained.app
Hooktheory

See the chords and melody of thousands of pop songs laid out on a timeline, and learn why progressions work the way they do.
- Learn
- Freemium
- hooktheory.com
keybr.com

Typing lessons that adapt to the keys you're worst at, generating pronounceable nonsense words until your weakest fingers catch up.
- Learn
- Free
- keybr.com
LanguageGuide.org

Hover over illustrated scenes to hear the word for each object spoken by a native speaker, in dozens of languages.
- Learn
- Free
- languageguide.org
muted.io

Clean, interactive music theory tools: a piano and fretboard for scales and chords, a circle of fifths and quick ear trainers.
- Learn
- Free
- muted.io
NB Chemistry Lab

A virtual chemistry lab in 3D: pick up glassware, mix reagents and watch the reactions happen without breaking anything.
- Learn
- Freemium
- chemistry-en.nobook.com
PCBX Simulator

Build Arduino circuits on a 3D breadboard in the browser, wire up displays and LEDs, and run real code against them.
- Learn
- Free
- pcbx.com
Skill-Lync Resources

Free mini courses on engineering topics like finite elements and fluid dynamics, with interactive diagrams instead of walls of formulas.
- Learn
- Free
- resources.skill-lync.com
Symbolab

Type in an equation, integral or proof and get the solution worked through step by step.
- Learn
- Freemium
- symbolab.com
Tiled.art

Escher-style tessellations from artists around the world, with animations that show how each shape interlocks and a tool to draw your own.
- Learn
- Free
- tiled.art
VisuAlgo

Step through sorting, graphs, trees and other data structures as animations, built by a university to teach algorithms.
- Learn
- Free
- visualgo.net
CarCareKiosk

Short how-to videos for almost any car's basics, from fuses to wipers to oil, filmed on the actual model you drive.
- Learn
- Free
- carcarekiosk.com
Class Central

A search engine for online courses across every university and platform, with reviews and a list of the ones that are actually free.
- Learn
- Free
- classcentral.com
Coddy

Bite-sized interactive coding lessons in Python, JavaScript, SQL and more, with a daily challenge to keep the habit.
- Learn
- Freemium
- coddy.tech
Codédex

Learn Python, HTML, CSS or JavaScript through a fantasy-style quest with pixel art, short exercises and badges.
- Learn
- Freemium
- codedex.io
Cymath

Type an equation, derivative or integral and get a full step-by-step solution, not just the answer.
- Learn
- Freemium
- cymath.com
edclub

The classroom edition of TypingClub: hundreds of typing lessons with games and progress tracking for schools.
- Learn
- Freemium
- edclub.com
Electude Simulator Challenge

Diagnose a broken engine with a virtual multimeter and wiring diagrams, the way trainee mechanics do. Scored against the clock.
- Learn
- Free
- simulator.electude.com
Hacksplaining

Short interactive lessons where you carry out real attacks like SQL injection and XSS yourself, then learn how to defend against them.
- Learn
- Free
- hacksplaining.com
Instructables

Step-by-step photo guides for making almost anything, from furniture to robots to cakes, written by the people who made them.
- Learn
- Free
- instructables.com
LingoHut

Free vocabulary lessons in dozens of languages with native audio, flashcards and listening games.
- Learn
- Free
- lingohut.com
Loecsen

Essential phrases in over fifty languages, each with an illustration and native audio. A no-pressure way to pick up the basics before a trip.
- Learn
- Free
- loecsen.com
MIT OpenCourseWare

Lecture notes, problem sets, exams and videos from thousands of real MIT courses, free to everyone and openly licensed.
- Learn
- Free
- ocw.mit.edu
Musicca

Free music theory exercises for reading notes, intervals and chords, plus a virtual piano, guitar and drum kit to try them on.
- Learn
- Free
- musicca.com
Photoskop

Learn aperture, shutter speed and lighting by playing with a virtual camera and studio, with the photo updating as you go.
- Learn
- Free
- photoskop.com
Toy Theater

Simple maths, reading and art games for young children, with virtual manipulatives that teachers actually use in class.
- Learn
- Free
- toytheater.com
TypingBird

Typing lessons and arcade-style games that build speed and accuracy, gentle enough for kids.
- Learn
- Free
- typingbird.com
Animagraffs

Long animated infographics that take apart a car engine, a fire truck or a city's water system and show every moving piece working.
- Learn
- Free
- animagraffs.com
Learning Synths

Ableton's playful course on synthesizers. Each lesson changes one knob on a synth in your browser, so you hear what oscillators, envelopes and filters do.
- Learn
- Free
- learningsynths.ableton.com
$Screenshot of Math is Fun$
Math is Fun

Plain-language, illustrated explanations of maths from counting to calculus, with puzzles and little interactive tools. Still the clearest on the web.
- Learn
- Free
- mathsisfun.com
Mathigon

An interactive maths textbook that talks back, plus Polypad, a virtual box of tiles, dice and number bars to explore ideas with your hands.
- Learn
- Free
- mathigon.org
musictheory.net

Short, clear lessons on notes, scales and chords, plus drills and ear trainers. The site music teachers have pointed students to for twenty years.
- Learn
- Free
- musictheory.net
OpenStax

Peer-reviewed college and high-school textbooks from Rice University, free to read online or download. Physics, biology, economics and more.
- Learn
- Free
- openstax.org
Project Euler

Hundreds of maths problems you can only solve with code, where the brute-force answer takes a week and the clever one takes a second.
- Learn
- Free
- projecteuler.net
BetterExplained

Maths taught the way it should have been the first time: intuition and analogy first, formulas afterwards. The essays on e and the Fourier transform are the classics.
- Learn
- Free
- betterexplained.com
Red Blob Games

Amit Patel’s interactive explainers on pathfinding, hex grids, noise and map generation. The A* article alone has taught a generation of game programmers.
- Learn
- Free
- redblobgames.com
Seeing Theory

Probability and statistics taught as things you drag: sample from a distribution, watch a regression line settle, see the central limit theorem happen in front of you.
- Learn
- Free
- seeing-theory.brown.edu
Cryptopals

Crypto challenges that teach you how ciphers break by making you break them yourself.
- Learn
- Free
- cryptopals.com
freeCodeCamp

Thousands of hours of coding curriculum, entirely free, with certifications and real projects.
- Learn
- Open source
- freecodecamp.org
Setosa — Explained Visually

Hard statistics concepts turned into things you can drag: eigenvectors, conditional probability, PCA.
- Learn
- Free
- setosa.io
Advent of Code

A December calendar of programming puzzles with a story, a leaderboard and a devoted community.
- Learn
- Free
- adventofcode.com
Khan Academy

Free, structured courses from arithmetic to art history, with practice that adapts to you.
- Learn
- Free
- khanacademy.org
The Evolution of Trust

A playable introduction to game theory that explains why cooperation appears, and why it collapses.
- Learn
- Free
- ncase.me
Grid Garden

The same trick as Froggy, but for CSS grid. Water your carrots with grid-column-start.
- Learn
- Open source
- cssgridgarden.com
Wolfram Alpha

A computational knowledge engine that answers questions with worked steps rather than links.
- Learn
- Freemium
- wolframalpha.com
Nicky Case

Playable posts about game theory, mental health and emergence that treat you as a participant.
- Learn
- Free
- ncase.me
Flexbox Froggy

Learn CSS flexbox by guiding frogs onto lily pads. Twenty-four levels and it finally sticks.
- Learn
- Open source
- flexboxfroggy.com
Desmos Graphing Calculator

A graphing calculator so fast and pleasant that it turns algebra into doodling.
- Learn
- Free
- desmos.com
Explorable Explanations

A hub for learning by playing: dozens of interactive essays on maths, society and systems.
- Learn
- Free
- explorabl.es
Exercism

Practice problems in seventy languages with free mentoring from real humans on your solutions.
- Learn
- Open source
- exercism.org
3Blue1Brown

Mathematics with a visual soul: linear algebra, calculus and analysis animated into real intuition.
- Learn
- Free
- 3blue1brown.com
Bartosz Ciechanowski

Long, gorgeous interactive essays explaining how gears, cameras, GPS and light actually work.
- Learn
- Free
- ciechanow.ski
OverTheWire

Security wargames played over SSH, starting from absolute beginner. The classic on-ramp.
- Learn
- Free
- overthewire.org
The Odin Project

A full-stack curriculum that makes you build things rather than watch someone else build them.
- Learn
- Open source
- theodinproject.com
Distill

Beautifully typeset, interactive machine learning research. Archived, but still the high water mark.
- Learn
- Free
- distill.pub

Lists with learn sites