Reference Library: Free Study and Research Links

Encyclopaedias and general reference

Wikipedia (opens in a new tab) The fastest way to get oriented on almost any topic. Follow its footnotes to real sources.
Encyclopaedia Britannica (opens in a new tab) Editor-reviewed articles you can safely cite when Wikipedia is not accepted.
Stanford Encyclopedia of Philosophy (opens in a new tab) Peer-reviewed, in-depth entries, the standard reference for philosophy essays.
Wikimedia Commons (opens in a new tab) Millions of freely licensed images and diagrams for presentations and projects.
Our World in Data (opens in a new tab) Clear charts and datasets on global topics, ready to cite in essays.
CIA World Factbook (opens in a new tab) Up-to-date country statistics (population, economy, geography) in one place.

OpenStax (opens in a new tab) Complete peer-reviewed textbooks you can download instead of buying.
MIT OpenCourseWare (opens in a new tab) Full MIT courses with lecture notes, problem sets, and exams to practise on.
Khan Academy (opens in a new tab) Short video lessons with instant practice, good for filling gaps before an exam.
LibreTexts (opens in a new tab) Huge open library of chemistry, biology, and maths texts organised by course.
Open Yale Courses (opens in a new tab) Recorded Yale lectures in full, strong for humanities and psychology.
Coursera (audit) (opens in a new tab) Most university courses can be audited free: skip the certificate, keep the content.
OpenLearn (opens in a new tab) Free Open University short courses with built-in self-assessment.

Wolfram Alpha (opens in a new tab) Solves equations step-free and answers computable questions. Great for checking work.
Desmos (opens in a new tab) Instant in-browser graphing calculator: see what a function actually does.
GeoGebra (opens in a new tab) Interactive geometry and algebra you can drag around to build intuition.
PhET Simulations (opens in a new tab) Physics and chemistry experiments you can run in the browser when there is no lab.
Wolfram MathWorld (opens in a new tab) Precise definitions and theorems when your textbook is vague.
NASA (opens in a new tab) Real mission data, images, and explainers for space and earth science projects.
PubMed (opens in a new tab) Search real biomedical research. Abstracts are free and citable.
Periodic Table (Ptable) (opens in a new tab) Interactive periodic table with properties, isotopes, and orbitals on hover.
3Blue1Brown (opens in a new tab) Visual explanations of calculus and linear algebra that make the ideas click.

Purdue OWL (opens in a new tab) The standard guide for APA/MLA citation rules and academic writing structure.
Merriam-Webster (opens in a new tab) Reliable dictionary with usage notes. Settles "which word is right" arguments.
Cambridge Dictionary (opens in a new tab) Definitions in plain English plus translations, kinder to non-native speakers.
Thesaurus.com (opens in a new tab) Fast synonyms when the same word keeps appearing in your essay.
Hemingway Editor (opens in a new tab) Paste a draft and it highlights sentences that are too long or too dense.
Zotero (opens in a new tab) Collects sources as you browse and formats the bibliography for you.
Etymonline (opens in a new tab) Word origins, useful for language essays and remembering vocabulary.

Project Gutenberg (opens in a new tab) Over 70,000 public-domain classics: every set text older than 1929, free.
Internet Archive (opens in a new tab) Borrow scanned books and revisit dead web pages via the Wayback Machine.
JSTOR (free reading) (opens in a new tab) Register free to read a quota of real academic papers each month.
World History Encyclopedia (opens in a new tab) Well-sourced ancient and world history articles written for students.
The British Museum (opens in a new tab) Search millions of objects from the collection with images and context.
Smithsonian Open Access (opens in a new tab) Millions of museum images and 3D models, free to reuse in any project.
Google Arts & Culture (opens in a new tab) Zoom into artworks in extreme detail and tour museums virtually.
Library of Congress (opens in a new tab) Primary sources (photographs, maps, newspapers) for history projects.

Wiktionary (opens in a new tab) A free dictionary in many languages, with full conjugation and declension tables.
WordReference (opens in a new tab) Bilingual dictionaries with forum threads on the phrases textbooks miss.
Forvo (opens in a new tab) Hear any word pronounced by native speakers before you say it in class.
Tatoeba (opens in a new tab) Millions of example sentences with translations, so you can see words used in context.
DeepL (opens in a new tab) Best-in-class machine translation for checking your own sentences.

Learning Scientists (opens in a new tab) Six study techniques that actually work, explained with printable guides.
Anki (opens in a new tab) Free spaced-repetition flashcards, the heavyweight option for long-term memory.
Pomofocus (opens in a new tab) A clean Pomodoro timer if you want one outside Brainlag.
Crash Course (opens in a new tab) Fast, funny video overviews of whole subjects, good before starting a topic.