Mathematics

Grant Sanderson’s channel and site explaining mathematics through animation — linear algebra, calculus, analysis. Unlike lectures it shows the picture behind the formula, not just the formula.

A resource opening the places people get stuck moving into abstract mathematics — reading definitions, the language of proof, notation. Unlike topic books it targets how mathematics is thought.

Olympiad-level competition-math courses and a forum community. Unlike school curricula it teaches olympiad-style problem solving rather than standard topics, with a strong student community.

A list organising mathematics resources by branch (algebra, analysis, topology). Unlike a single course it maps out where to start.

A set of essays explaining maths by intuition rather than memorisation — exponentials, Euler’s formula, calculus. Unlike formal treatments it answers “why is it like this” with analogy and pictures.

A free online graphing calculator producing fast, shareable interactive graphs. Compared with GeoGebra it is simpler and graph-focused — for plotting a function and sliding parameters to see the result instantly.

An EMS/Springer-backed maths wiki of authoritative survey articles. Unlike Wikipedia the entries are written and vetted by experts — research-level rigour.

A free UBC text building linear algebra from the ground up. Unlike short notes it is a complete, proof-carrying resource for those who want the reasoning behind the course.

Dynamic maths software that links geometry, algebra and calculus live. Unlike Desmos it offers a broader toolset beyond graphing — geometric construction and 3D included.

Draw a graph in the browser and run shortest path, connectivity and flow algorithms on it. Unlike VisuAlgo it lets you build your own graph and run algorithms on it rather than preset examples — without writing code.

A site teaching mathematics topic by topic with interactive graphs and worked examples. Unlike static notes you can move the graph in place and see the result.

A free platform teaching mathematics from primary school to university, with exercises in order. Unlike scattered videos it offers a full curriculum that builds on prior topics.

The community edition of the Python library behind the mathematical animations in 3Blue1Brown videos; you describe the scene in code. Unlike general animation tools it treats equations, graphs and transformations as first-class objects.

Jeremy Kun’s blog joining mathematics with working code — cryptography, graphs, the maths of machine learning. Unlike pure theory it closes each concept with an implementation.

A cheat sheet mapping mathematical notation to readable code: sigma sums, dot products. Unlike symbol glossaries it shows what the formula means to a programmer.

An approachable graduate-maths blog that builds intuition for abstract topics. Unlike textbooks it builds intuition before formalism, opening topics such as category theory with pictures and analogy.

A mathematics Q&A site where you can ask experts about the step you are stuck on. Unlike a forum, voting surfaces the clearest solution.

An interactive maths textbook with manipulable, story-driven lessons. Unlike printed textbooks the reader moves the objects at each step and sees the result.

A high-rigour question-and-answer site for research mathematicians. Unlike Math Stack Exchange it targets research-level questions — not homework, but open mathematical problems.

An MIT course gathering the discrete mathematics a computer scientist needs — logic, counting, graphs, probability — in one place. Unlike general maths courses it aims straight at CS.

The Online Encyclopedia of Integer Sequences — look any sequence up by its terms. Unlike general maths references it allows reverse lookup: from a few numbers you find the formula and name.

A free, open textbook for introductory statistics, covering data, inference and regression by example. Unlike commercial texts it is free and comes with exercises and slides.

Clean, worked lecture notes for algebra, calculus and differential equations (Lamar University). Unlike a textbook it is ideal for a quick refresh before an exam.

A cheat sheet compressing a probability course’s distributions, expectations and theorems onto one page. Unlike a textbook it can be scanned at a glance during an exam.

A collaborative maths database holding proofs, not just statements.

A Brown University project teaching probability and statistics entirely through interactive visuals. Unlike a textbook you see the concept by dragging and trying — you move the distribution by hand.

A Stanford reference summarising the linear algebra needed for machine learning. Unlike a full course it is a quick refresher focused only on the parts ML uses.

An equation solver that shows the worked steps to a solution, derivatives, integrals and limits included. Unlike general computation engines it centres on the steps rather than the answer; some detailed steps are paid.

An extensive, rigorous and cross-linked mathematics encyclopedia. Unlike Wikipedia it is written under one hand (Wolfram) with consistent notation and depth; compared with the Encyclopedia of Mathematics it is more accessible.