Anki
apps.ankiweb.net
Schedules flashcard reviews for the day before you would have forgotten them
Free account
Loading page
Courses, practice, languages and things worth knowing.
apps.ankiweb.net
Schedules flashcard reviews for the day before you would have forgotten them
desmos.com
Type an equation and watch the curve, with a slider for every parameter
duolingo.com
Turns a language into five-minute daily drills you will actually keep doing
exercism.org
Practice exercises in 80-odd languages with free feedback from a human mentor
freecodecamp.org
Teaches web development by making you write code in the browser from lesson one
khanacademy.org
Explains school maths and science one short video and one exercise at a time
ocw.mit.edu
Publishes the real lecture notes, problem sets and exams from MIT courses
monkeytype.com
A typing test you can tune to the exact words, punctuation and length you want
musictheory.net
Free lessons and endless drills for notation, intervals, chords and ear training
openstax.org
Peer-reviewed university textbooks you can read online or download as PDFs
wikipedia.org
Gets you oriented on almost any subject, with the sources listed at the bottom
wolframalpha.com
Answers a maths, science or unit question typed as an ordinary sentence
Privacy
These process everything inside the browser. Load the page, disconnect from the network, and they still work.
desmos.com
Type an equation and watch the curve, with a slider for every parameter
monkeytype.com
A typing test you can tune to the exact words, punctuation and length you want
By task
Archive
Kept on record so an old bookmark still leads to an answer. Each one names the site that does the job now.
askeet.com
Community questions and answers ranked by member voting
Questions
There is no single answer, which is why this page lists 12 of them with their limits stated. If you want to avoid signing up entirely, 6 of these work with no account at all.
2 of the 12 sites here process your file inside the browser and never upload it — they are marked "On device". The rest send your input to their server, which is fine for public material and worth thinking twice about for anything personal.
Some already have. 1 entry in this category has been retired and moved to the Archive with a working successor, so an old bookmark still leads somewhere useful.