For the moment a lecture loses you
Paste any lecture. When something doesn't click, start typing or just ask out loud. Lumo pauses the video, explains that exact moment with a diagram, checks you've got it, and remembers what you struggle with all semester.
Free to start. Works for every subject.
So as we nudge x forward by a tiny amount…
Area under a curve and the derivative
Intro to Calculus
Confused? Just start typing.
Used by students from
Any lecture or explainer. We take notes on the whole video once, what's said and what's on the board.
Your first keystroke freezes the video and pins your question to that timestamp. No rewinding, no retyping context.
A short answer in plain language, plus a visual when it helps: the real frame annotated, a graph, or a step-by-step sketch.
More than answers
Lumo watches with you, figures out why you're stuck, teaches it the way that works for you, and remembers it all semester.
Keeps forgetting the inner derivative (seen 3×)
It tracks what you've mastered, what's fading, the mistakes you keep making, and which explanations work for you, so month three starts where month two ended.
how do I solve this?
Before calculating, what does the problem give you?
the rate the radius grows
✓ Right. What equation links radius and area?
Lumo asks the question that gets you to the next step, checks your answer, and switches to a hint, an example or a full explanation when you need it. Or tap Just explain.
Lumo writes, draws, graphs and circles things step by step. Draw your attempt and it sees exactly where you went wrong.
Find the derivative of (3x − 1)⁴
targets a mistake you've made
Chain rule mastery 45% → 62%
The next problem is picked for you: easier when you're stuck, harder when you're ready, and built to fix the mistake you just made.
“Wait, why did they cancel that?”
❚❚ Lecture paused at 12:03 · resumes when you've got it
Say “wait, why did they cancel that?” The video pauses, Lumo explains, asks a quick check, and picks the lecture back up.
PHYS 7A
Midterm Oct 8
Exam in 5 days
Today: Newton's laws, Friction
Tomorrow: Energy conservation
Final review: Your 4 weakest topics
Drop in your syllabus, slides, homework and past exams. Lumo builds the course map and a day-by-day plan for exam week.
Quick review
You haven't reviewed rotational dynamics in 6 weeks. Let's see what you remember.
Lumo schedules quick checks when your memory of a topic starts to fade, which makes it stick far longer than cramming.
Graphs and 3D surfaces, molecules and reactions, forces drawn to scale, and step-by-step trees, stacks and pointers.
Two real kinds of questions, answered the way a good TA would sketch them on a napkin.
“what does 'the limit of the secant' even mean?”
“why is water bent and not a straight line?”
If it's taught on video, you can stop and ask about it.
Flip a card. In the app, Lumo answers at the exact moment in your lecture, with a diagram when it helps.
AP Calc, AP Bio, AP Chem and SAT review videos. Ask the question you'd feel awkward raising in class.
Recorded lectures, problem-set walkthroughs, and the 2 a.m. study session when office hours are long over.
Every question you ask is saved with its timestamp and diagram, so your confusions turn into a review sheet.
LumoTutor Plus · $9.99/month
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Invite 2 friends, unlock 14 days of Plus. Share your link in your class group chat once you sign up.
Fitting, really. Still curious? Paste a lecture and ask the tutor.
Public videos on YouTube and Vimeo, plus lecture video files hosted by universities (.edu) and the Internet Archive. Other sites are blocked for now to keep things safe. For Vimeo, turn on exact diagrams so the tutor can see what's playing.
The first time anyone adds a video, we take notes on what's said and shown throughout it. When you ask, the tutor also watches the 30 seconds right before your pause, so it knows the exact graph, equation or diagram you're looking at.
If you allow it, the app captures the single frame you paused on and the tutor draws directly on it: circling the term, pointing at the curve, labeling the strip. Nothing is recorded while you watch. You can turn it off with one click.
All of them. Math and science get graphs and annotated frames, processes get flowcharts, and essay-style subjects like history or psychology get clear written explanations tied to the moment in the lecture.
Only when you start typing a question. The moment your first key goes down, the video stops and your question is pinned to that timestamp. Hit Resume or press space to keep going.
Yes, like any AI it can make mistakes. Every answer links back to the exact moment in the video so you can check it, and you can flag answers that miss.
Yes. Free includes 2 lectures a month, 100 tutor questions and 40 practice problems. Plus ($9.99/month or $79.99/year) unlocks 25 hours of lectures, 600 questions a month, voice tutoring, diagrams, adaptive practice, memory and exam prep. Pro ($19.99/month) doubles that and uses the strongest models on hard problems. Invite 2 friends and you get 14 days of Plus free.
Only you. Questions, answers and captured frames are private to your account.