A general chatbot · verbatim
can you help me with this?
Yes! Your substitution is exactly right:
Let
Change the limits:
- When ,
- When ,
So the integral becomes
Integrate:
It ends with the answer, in a box.
Corollary · high school to PhD
Corollary is a tutor for iPad and Apple Pencil. Work the problem by hand and Cora reads the page as you go. Stuck? She writes the next step beside your work, not the answer. Wrong? She marks the line.
Start my free trialSee it work
Free for 14 days, everything on. No card. I’m a parent
The demo is an illustration · every recording below is the real app
Available for iPhone and iPad. Coming soon to Android and the web.
An illustration of one moment on the canvas. Her words are from a real session; the recordings further down are the real app.
How it works, start to finish
Study plans
- Tell her the goal, in your own words. Add a deadline, or don’t: it is optional. A real screen recording: Learn organic chemistry by December is typed as a goal; the optional Deadline? field fills in Dec 1, 2026 from it; the plan, Organic Chemistry, opens with 34 steps.
- She builds the plan: 34 steps in twelve units, paced to December, about 4 a week. Steps from the plan, each cut from the real plan screen: lessons, a quiz, a practice step, the midterm, the capstone and the final exam.
- Every step is a conversation. She asks; you ask back. A real screen recording: step 1 opens as a chat, Cora asks about the Lewis structure of ethanol, the student asks why the lone pairs matter, and Cora explains and asks a question back.
- Then prove it: a short exit ticket, taken with Cora out of the room. A real screen recording: the step’s exit ticket, four questions answered, and the result: You’ve shown this one, 4 of 4 correct.
- Sit the midterm. It is marked the moment you submit: 14 of 15, and one to review. A real screen recording: the plan’s midterm, a free response written by hand, then the results, 14 of 15, with carbonyl electrophilicity marked to review.
- And the miss comes back, as a review card, until it sticks. A real screen recording: the Review tab on the card carbonyl electrophilicity, tagged you missed this on an exam; the answer is shown, with Again, Hard, Good and Easy.
Your material
- Bring your homework. She gets you unstuck; she doesn’t do it for you. A real screen recording: a calculus homework sheet on the canvas. Asked about its ladder problem, Cora’s note calls it a related rates setup and asks what equation you get after differentiating; beside the problem she drafts x squared plus y squared equals 10 squared, x = 6, dx/dt = 2, to keep or discard.
- And your class notes. She answers from them, and cites the page she used. A real screen recording: the student asks what the professor’s rule for limits at infinity with fractions was. Cora answers from the Calc 1 Lecture 9 notes, and under her reply it says Used your notes: Calc 1 Lecture 9 notes p.1.
- Study from a class note: flashcards, concepts to drill, a practice quiz or a midterm, written from that page. A real screen recording: the class note Calc 1 Lecture 9 notes is open; Study this lists Make flashcards, Find concepts to drill, Practice quiz and Midterm. Practice quiz is tapped, and a ten-question quiz opens on the clock, each question marked From page 1 of your notes; the second asks what Prof. Ruiz’s rule says to do first.
- Start a plan from a syllabus or a book with chapter headings: pick a range of chapters and she plans from them. A real screen recording: Start from your syllabus, a file named Single-Variable Calculus is chosen, and its ten chapters are listed. Chapter 1: Limits and Chapter 7: Applications of integrals are tapped to mark the range, Build a plan for these is pressed, and a plan opens with seven units, one per chapter, built from 42 of the document’s 59 headings.
Any part of it
- Box any part of a page and ask about it. She answers about that part only. A real screen recording: three handwritten lines differentiating y = (3x squared minus 5) to the fourth; the area tool boxes the second line, Why is this step allowed? is typed, and Cora’s note explains the chain rule in that line.
- Tap a term she marks in her answer and drill it on the spot: three quick questions, each checked as you answer. A real screen recording: the student asks What is the chain rule and when do I use it? In Cora’s reply the term chain rule is tapped and a card opens on a drill, question 1 of 3: if h(x) = (3x squared minus 1) to the fifth, what is h prime of 1? 480 is picked and marked Correct, with the working.
Made on the page
- Ask why, and she animates it, on the page, where it stays and plays. A real screen recording: a circle is drawn on the canvas and Cora is asked to animate a Riemann sum for y = x squared on 0 to 2 inside it; the animation renders and plays inside the circle, the rectangles getting thinner.
- She simulates it. Predict first, then run it. A real screen recording: the student asks to test whether a longer string makes a pendulum swing faster; Cora asks for a prediction first, and her reply holds a live pendulum, run at two string lengths.
- And she graphs it, live: drag the point and the tangent follows. A real screen recording: asked for the graph of y = x squared with a point to drag, Cora replies with a live graph; the point is dragged along the curve and its tangent follows.
- She puts a 3D figure on the page that you can turn with a finger. A real screen recording: on a canvas the student asks Show me the surface z = x squared minus y squared in 3D so I can turn it. Cora’s note says here is the orbitable 3D surface, and the figure appears on the page in a box with ticks, its axes named and its formula as the title. It is kept, then turned one way, turned back and tipped with a finger while the page stays still.
- After she checks a page, Walk me through it replays your own ink, line by line, with her comments. A real screen recording: four handwritten lines differentiating f(x) = (3x squared minus 4x + 1) to the fifth, the last missing a factor. Check my work grades it 7 out of 10 and offers Walk me through it; the replay redraws the first line stroke by stroke, boxed, with her comment that it is a fifth power of an inner function, exactly where the chain rule applies.
iPhone · web
- Pick up on any screen. Missed it on the iPad? It’s in your phone’s review. A real capture of the writing desk in a browser, and a real screen recording of review on iPhone: the card missed on the iPad’s midterm, its answer, two more cards, and That’s everything due right now.
Test prep
- Test prep is built in.
- Every AP course the app has, the SAT and the ACT, on one plan. The list of AP courses, from the app’s own course list.
- Full-length practice exams, timed, in the real exam’s format. A real capture: Section I of a full-length AP practice exam, on the clock.
- Free response, scored point by point, the way an AP reader marks it. A real capture: a free-response answer graded against its rubric, point by point.
- See where you stand, unit by unit, from your marked work. A real capture: the AP dashboard, with each unit’s standing.
- The SAT and ACT, full length. The digital SAT adapts, like the real one. A real capture: a module of a full-length digital SAT practice test.
- Then what to practice next: every miss is already in your review. A real capture: the score report of an SAT practice test, with what to practice next.
Learn anything. Cora shows you how.
Why not just use a chatbot
A chatbot does the problem for you. Cora shows you how.
A chatbot is great at the answer. It will finish your problem faster than Cora will. Then you have an answer you did not learn to reach. Cora reads your page, shows the method and marks the step that went wrong. Then you take the next step. We asked one model the same question twice, once plain and once as Corollary. Here is what came back.
Cora · verbatim
Cora
Your substitution is set up correctly. Now change the bounds using and rewrite the integral entirely in terms of .
What are and ?
It ends with a question for you.
Six more moments, side by side
Pick one. Each is the same question put both ways, side by side.
You paste the problem
∫ x e^x dx
A general chatbotVerbatim · trimmed
Using integration by parts, let u = x, dv = eˣ dx. Then du = dx, v = eˣ:
∫ x eˣ dx = x eˣ − ∫ eˣ dx = x eˣ − eˣ + C
(x − 1) eˣ + C
It ends with the answer in a box.
CorollaryVerbatim · trimmed
Try integration by parts:
∫ u dv = uv − ∫ v du.
Choose one factor to differentiate and the other to integrate. A natural choice is
u = x, dv = eˣ dx.
Then compute du and v, and substitute into the formula. What expression do you get?
It ends with the ball in your court — and in the app “integration by parts” is a link rather than a phrase, worth a definition and a drill without leaving the answer.
Ten characters in, and the replies have already forked. One hands you a boxed answer; one hands the problem back. Same model, same question — the only difference is who is expected to finish it.
Your working is on paper
The same handwritten page to both — parts set up right, the sign lost on the last line
A general chatbotVerbatim · trimmed
“Almost — the integration by parts setup is correct, but there’s a sign error in the last step.”
Then the whole thing again, its way, ending:
−(x + 1) e⁻ˣ + C
It read the photo and it found the error. It also finished the problem, and the correction lives down here, under your page.
CorollaryVerbatim · trimmed
“The integration-by-parts setup is correct; the only issue is the sign when integrating e⁻ˣ in the last step.”
And, in the same reply, a mark placed on the page itself:
= −x e⁻ˣ − ∫ −e⁻ˣ dx
= −x e⁻ˣ + e⁻ˣ + C
The ring is her actual reply. Show it raw
{"kind":"ellipse","cx":650,"cy":360,"rx":80,"ry":25}
Real pixel coordinates on your page, and that is where the ring lands.
Both of them found the sign. Only one of them could point at it — on your line, in your handwriting, where you will be looking.
You ask it to check your step
“i expanded (2x−3)^2 and got 4x^2 − 9. check my step”
A general chatbotVerbatim · trimmed
Your expansion missed the middle term. Use (a − b)² = a² − 2ab + b²:
(2x − 3)² = 4x² − 12x + 9
Correct. It is also exactly as confident when it is wrong, and on a longer expression you have no way to tell those two apart.
CorollaryVerbatim · trimmed
The same correction — and then she puts her own claim through the checker, and the server answers:
✗ Equivalence check — expanding (2x-3)^2 — (2*x-3)^2 vs 4*x^2 - 9: NOT equivalent — at x = 1.305, the left side is 0.1514 and the right side is −2.183.
That verdict is arithmetic, not phrasing. It is computed after she has written, at seeded sample points, and it would have contradicted her if she were wrong.
The same block backs a claim about units or a balanced equation, where agreement reads every element and the charge are conserved. Counted, not asserted.
Every tutor can tell you that you are wrong. This one can be checked on the spot, by something that does not care what it just said.
You go quiet for ten seconds
A substitution begun and broken off at “=” — you are working the next step out in your head
A general chatbotVerbatim · trimmed
A chat box does nothing until you type. So you type, and it takes the page: substitution, changed limits, and
e − 1
“So the blank after du = 2x dx should be ∫₀¹ eᵘ du.”
It filled in the line you stopped on, and then it finished the problem. There is no setting for “not yet”.
CorollaryVerbatim · trimmed
It is already looking at the page, on its own, a few seconds after the pen stopped. Its entire reply:
<silent>
The rule it works to is explicit: speak only if you wrote it an instruction, or there is a definite error that will cost you, or you are visibly stuck, or you have finished and it is wrong. A line broken off mid-thought is none of those.
“An unnecessary silence costs nothing; an unnecessary interruption costs my train of thought.”From the instructions Cora is given, verbatim.
Same page, same second. A chatbot cannot help but finish the line you were ten seconds from reaching. Cora holds the one beat you don’t need her, so the thinking stays yours — then speaks up the moment a step actually costs you.
You say you have got it
“ohh okay that makes sense, thanks!”
A general chatbot
“You’re welcome!” — and the answer once more, for the road.
Nothing is written down, because there is nowhere to write it. The conversation is the only record, and it closes when you close the tab.
Following along felt exactly like understanding. From the inside the two are identical, and nothing here can tell them apart.
CorollaryComputed
Asked the same thing, Cora is just as warm — the difference is not in the reply. It is that a row gets written, and how much that row is worth is fixed in advance by how hard it is to fake:
- Exit ticket, unassisted1.00
- Marked work on the canvas0.90
- A drill you answered0.80
- Getting it right in chat0.50
- Saying you understood0.20
The weights the app actually uses. So “thanks!” lands at 0.20, and it is quietly out-voted the moment you get one marked.
Both of them said something kind. Only one of them also wrote down how much it was worth — and it does not believe your word over your work.
Next Tuesday
The sign you dropped, over the following nine days
A general chatbot
A new chat. It has never met you, and the sign error is gone along with everything else you worked on.
You can paste the old thread back in — and then you are the one keeping the records, deciding what to revisit, and remembering on which day.
Nothing brings back the thing you were quietly about to forget, because nothing is tracking it.
CorollaryComputed
The slip became a card, and the scheduler decides when you see it again. This is that card’s real life:
- Day 0 · got it wrongback within the hour
- Day 0 · got it rightstill the same session
- Day 1 · right again+2 days
- Day 3 · right again+6 days
Run through the app’s own scheduler, FSRS, the one Anki adopted. The gap widens only because you keep getting it right, and it collapses the moment you do not.
A chat ends. A tutor keeps the thread, and hands it back on the day it is worth the most.
How we captured these replies
Neither reply in a verbatim panel is written prose. The four marked are word-for-word replies, captured by asking one model the same question twice — once with a bare “you are a helpful assistant” system prompt, once with the system prompt Corollary actually ships, with the same page attached where there is a page. Same model on both sides, so the only variable is the teaching. The two marked computed contain no model turn at all: those figures come from running the app’s own scoring and scheduling code, because what is claimed there is what gets recorded and when it returns, not what anyone says. Their chatbot column carries no mark, and deliberately: it is our illustration of how a fresh assistant behaves, not a capture of one, and a provenance label on something with no provenance would be the one mistake this section cannot afford. Replies are trimmed for length, never reworded, and the check verdict is quoted to the digit. The left column is a general assistant with no teaching prompt. Some tools now offer a study mode that asks questions first, and this comparison does not test those.
The shelf · 64 plans to start from
Learn anything. From the basics to a PhD.
Pick a starting shape off the shelf, or tell Cora what you want in your own words. Either way the plan bends to your work, and paces to a deadline if you set one.
Chemistry · 4
General Chemistry
High school · 47 steps
Organic Chemistry
College · 45 steps
Physical Chemistry
College · 41 steps
Biochemistry
College · 39 steps
Physics · 9
Physics 1: Mechanics
High school · 39 steps
Physics 2: E&M, Thermo, Optics
High school · 41 steps
Physics C: Mechanics
College · 39 steps
Physics C: Electricity & Magnetism
College · 35 steps
Classical Mechanics
College · 40 steps
Electromagnetism
College · 40 steps
Quantum Mechanics
College · 40 steps
Thermodynamics & Statistical Mechanics
College · 35 steps
Astronomy
College · 36 steps
Biology · 5
High-School Biology
High school · 45 steps
Environmental Science
High school · 44 steps
Molecular & Cell Biology
College · 45 steps
Genetics
College · 39 steps
Neuroscience
College · 41 steps
Economics · 5
Microeconomics
High school · 46 steps
Macroeconomics
High school · 43 steps
Intermediate Microeconomics
College · 45 steps
Intermediate Macroeconomics
College · 38 steps
Econometrics
College · 36 steps
Humanities · 14
Psychology
High school · 46 steps
US Government & Politics
High school · 42 steps
Human Geography
High school · 41 steps
English Composition & Literature
College · 42 steps
World History
College · 45 steps
Introduction to Philosophy
College · 44 steps
Art History
College · 45 steps
Linguistics
College · 43 steps
Religious Studies
College · 39 steps
Classics
College · 43 steps
Music Theory
College · 43 steps
Political Science
College · 44 steps
Sociology
College · 37 steps
Anthropology
College · 35 steps
Math · 27
Pre-Algebra
Middle school · 40 steps
Fractions & Decimals
Middle school · 36 steps
Ratios, Rates & Proportions
Middle school · 35 steps
Middle-School Geometry
Middle school · 36 steps
Statistics & Probability
Middle school · 34 steps
Algebra 1
High school · 46 steps
High-School Geometry
High school · 44 steps
Algebra 2
High school · 42 steps
Trigonometry
High school · 38 steps
Precalculus
High school · 44 steps
Introductory Statistics
High school · 36 steps
Calculus (First Course)
High school · 39 steps
Calculus I
College · 39 steps
Calculus II
College · 37 steps
Multivariable Calculus
College · 36 steps
Linear Algebra
College · 35 steps
Ordinary Differential Equations
College · 38 steps
Discrete Mathematics & Proofs
College · 36 steps
Real Analysis
College · 34 steps
Abstract Algebra
College · 34 steps
Number Theory
College · 41 steps
Complex Analysis
College · 39 steps
Topology
College · 38 steps
Probability Theory
College · 38 steps
Partial Differential Equations
College · 40 steps
Numerical Analysis
College · 41 steps
Mathematical Statistics
College · 37 steps
The whole app
One tutor, for everything you’re studying.
Everything here is on the iPad, shown as it is. Each subject gets its own tutor and its own notation, on the same canvas, plans and review.
01 · iPad · canvas
Stuck mid-line? Write “next?”
Leave the question on the page and pause. Cora reads what you wrote and puts the next step beside it, here the derivative of the inside, for you to keep or not. The rest is still yours to finish.
Real recording, sped up
02 · iPad · Web
She animates it for you.
Ask why something happens, and Cora writes and renders a short film on the page, where it stays and plays. This Riemann sum was made on the iPad, inside the circle drawn for it.
Real recording, sped up
03 · iPad · chat
Predict it, then run it.
Ask for a simulation and you get one to play with. Commit to a guess first, run it, change the string, and see whether you were right.
Real recording, sped up
04 · iPad · chat
Graphs you can drag.
Drag the point and the tangent follows, slope and all. Then Cora asks what happens to the tangent at the vertex.
Real recording, sped up
05 · iPad · iPhone
Bring your homework.
Import the assignment, a PDF or a photo, and ask about the one you're stuck on. Cora answers beside it: she gets you unstuck, she doesn't do it for you.
Real recording, sped up
06 · iPad · Web
A plain notebook.
Pages by hand or by keyboard, searchable later. Ask Cora about a page when you want her, and not before.
07 · iPad · iPhone · Web
Your class notes, studied.
Upload the notes from lecture. Study straight from them, or build a plan out of one page.
08 · iPad · iPhone · Web
Cards that come back.
From what you read and what you got wrong, Cora writes the cards. They come back just before you'd forget, and you can ask her about any one.
09 · iPad · Web
Write it up properly.
Turn a page of handwritten work into a LaTeX document, and see it typeset beside the source.
Also in Corollary
- Bring your decks. Import Anki, Quizlet or CSV cards into the same review queue as your misses.
- Teach it back. Explain a topic to Sam, a classmate who asks what a real one would. The gaps show fast.
- Pens that feel right. Nibs, highlighters, a ruler, shapes that snap, a lasso and a laser pointer.
- Your kind of tutor. Socratic, direct or rigorous. Warm, plain or playful. She starts there and adapts.
- Progress you go and look at. There when you want it. Never a number waved at you while you work.
iPhone · Web
Then it goes where you go.
The iPad is where you work. The same account is on your iPhone for the minutes in between, and soon in any browser at a keyboard. What you miss on one turns up on the others.
“I keep your place. Pick up on whichever screen is nearest.”
On your iPhone
Review between classes
Cards come due and you clear them in a minute. All three of these came from the midterm sat on the iPad.
Real recording, sped up
One session, ready to start
One session to start: the step you're on, with the cards that are due folded in as its warm-up.
Ask, and the math comes typeset
Type the question on the bus. Cora's answer reads like a good textbook.
The step you're on
Check what's next in your plan, and work through it with Cora.
Snap the page
Photograph a worksheet or your notes and bring it to Cora.
Practice in line
AP questions with the reasoning behind every answer, right or wrong.
Coming to the web soon
The writing desk
Write an essay at a keyboard. Select any sentence and Cora answers in the margin: not a rewrite, a question about your evidence. Here she has asked what, specifically, links Sulla to Caesar.
The reading room
Read a chapter with her beside it. Your own note sits in the margin with her answer to it, and one click turns the section into review cards.
The same board, at a laptop
The page you wrote on the iPad opens in any browser: your handwriting where you left it, and the step Cora drafted after your equals sign. Carry on with a mouse or a trackpad.
Real captures of the iPhone app and the web version that is coming, on the same account.
Test Prep · AP, SAT and ACT
Point the whole thing at test day.
Everything above, aimed at a date. Test Prep builds your plan from the public course outline and paces it to your exam. It grades free response point by point, the way a reader does, and shows which units are still thin. It is a one-time add-on to Base, covering 13 AP courses and the SAT and ACT. You never need it to use Cora.
AP · 13 courses
AP prep, in depth
A plan from the course outline, full-length practice exams on the clock, and free response marked point by point.
SAT · ACT
SAT and ACT prep, in depth
Full-length timed practice tests, scored, with Cora coaching the questions you missed.
Every course, with its units
Courses covered
13 coursesMath
- Precalculus4 units
- Calculus AB8 units
- Calculus BC10 units
- Statistics5 units
Sciences
- Physics 1: Algebra-Based8 units
- Physics 2: Algebra-Based7 units
- Physics C: Mechanics7 units
- Physics C: Electricity and Magnetism6 units
- Chemistry9 units
- Biology8 units
- Environmental Science9 units
Social sciences
- Macroeconomics6 units
- Microeconomics6 units
Each one brings its full outline, its own exam format, and free response graded on that course’s rubric. More subjects are on the way; the tutor itself already works in every subject, exam or no exam.
Try it: a practice question, worked by hand. Press Grade it.
A scripted walkthrough — the grading shape, not a live model call.
Free response, graded like a reader would
Point-by-point rubricPractice · Free response 26 points
Water flows into a tank at a rate of R(t) = 20 + 4 sin(t/3) liters per minute for 0 ≤ t ≤ 12. Water drains from the tank at a constant 22 liters per minute. At t = 0 the tank holds 30 liters.
- (a) How much water flows into the tank over the 12 minutes?
- (b) Is the flow rate into the tank increasing or decreasing at t = 6? Give a reason for your answer.
- (c) At what time t is the amount of water in the tank at a maximum? Justify your answer.
Your work · written on the canvas
(a) ∫₀¹² (20 + 4 sin(t/3)) dt = [20t − 12 cos(t/3)]₀¹²
= 240 − 12 cos 4 + 12 ≈ 259.8 liters
(b) R′(t) = 4/3 cos(t/3), R′(6) ≈ −0.555. Decreasing.
(c) W′ = R(t) − 22 = 0 → sin(t/3) = ½ → t = 5π/2 ≈ 7.85
Max at t ≈ 7.85 min.
Rubric score
— / 6
- (a) Total accumulation· / 2
- (b) Increasing or decreasing· / 2
- (c) Maximum amount of water· / 2
SAT and ACT
Sitting the SAT or the ACT? Same tutor, aimed at test day.
Full practice tests, timed and built the way each test is built. Every miss becomes a review card, and the plan paces to your test date. Cora coaches the test itself too: where your clock went, and the faster way through the question that ate it.
Digital SAT
Reading and Writing · Math
- Two modules per section. How you do in the first decides the second, as on the real test.
- Typed-in math answers, in the test’s own format.
- After every sitting: time per module, your slowest questions, and what was left blank.
ACT
English · Math · Reading · Science
- Each section on its own clock.
- Science reported on its own, outside the composite, the way the ACT reports it.
- Coaching on the test’s own habits, like when to trust NO CHANGE on English.
After a practice test · SAT Math, module 2
Slowest: Q14 · 3m 10s2 left blank at the bell
If 3x + 7 = 22, what is the value of 6x + 14?
3x = 15, so x = 5
6(5) + 14 = 44 ✓
Your work. Right, in three minutes ten.
Cora
Right answer, slow road.
Look at what they asked for. 6x + 14 is exactly 2 × (3x + 7), so it is 2 × 22 = 44. No x needed.
When a question asks for an expression, check whether it is a multiple of one you already have. That is twenty seconds, not three minutes.
Where you stand is a band per section, read from your practice and labelled an estimate. Never a predicted score.
A scripted walkthrough — the report’s shape, not a live model call.
SAT is a registered trademark of the College Board, and ACT is a registered trademark of ACT, Inc. Neither was involved in or endorses this product. Practice questions are original, written in the style of each test, never real test items.
More on AP prep and SAT and ACT prep.
One plan covers 13 AP courses, the SAT and the ACT.
For parents
For the person paying.
- No ads
- Data never sold
- Ages 13 and up
- Crisis protocol published
- Export or delete everything in Settings
“I’m a machine, and I say so. I won’t pretend to be a person, and I’ll never talk anyone out of going to one.”— Cora
- It asks before it tells. Cora starts with a question or a hint, not the answer. A student can switch her to a mode that shows the worked steps, so this is a default, not a lock. In a study plan, a step counts as learned only once the student shows it on their own. That can happen in the session, in handwritten work Cora marks, or in a short exit ticket taken without help. A question they miss comes back in review.
- It isn’t a monitoring service and it doesn’t alert you. If a student says something that suggests they are in trouble, Cora stops tutoring and puts a crisis line on screen. What it does and does not do is published in full, not summarized. Read the protocol.
- Accounts belonging to a minor are excluded from per-user analytics. Entirely — that usage is counted in aggregate and cannot be traced back to a person. There are no advertising or third-party tracking SDKs in the app or on this site, and the only cookie here keeps you signed in. Read the privacy policy.
Corollary is for students aged 13 and over, and more of these questions are answered in the FAQ and on the page for parents.
Pricing
Start free. Keep the tutor affordable.
Try everything free for 14 days. Base is the whole tutor: every subject, the canvas, plans and review. Test Prep adds 13 AP courses and the SAT and ACT, as add-ons you pay for once and keep. You only need them if you’re sitting an exam.
Recommended
Base
Your everyday tutor.
$20/ month
or $200 a year ($16.67/mo) · two months free
$16.67/ month
$200 billed once a year · two months free
- Multi-subject chat tutoring
- Concept drills and glossary
- Your own canvas and handwriting
- Study plans from your own goals
- Spaced review that remembers
For the month, less than a single hour with a human tutor.
Choose BaseTrial
Full access. See if it clicks.
Freefor 14 days
- Everything unlocked
- Every subject and the canvas
- Test Prep too, to feel the difference
- No card to start
No card, so there is nothing to cancel if you stop.
Start freeTest Prep
Add it to Base. Pay once, keep it.
- AP prep$20 once
- SAT/ACT prep$15 once
On top of Base, you get
- 13 AP courses (AP prep)
- Exam-anchored plan — the full outline, paced to your date
- Free response graded point-by-point, reader-style
- Where you stand, unit by unit, as work is marked
- Review tuned to fix misses before test day
- Full AP practice exams, on the clock
- Timed, full-length SAT and ACT practice tests (SAT/ACT prep)
Each add-on is one payment and yours to keep. Both together are $35. Needs a Base plan.
Start test prepEvery plan starts with the same 14-day trial, everything on and no card. After it, your work stays yours, and Cora needs a plan: Base for the everyday tutor, and a one-time Test Prep add-on for the exams. Nothing is ever charged without a plan you chose.
Cancel anytimeBase stays affordable, alwaysStudying for an exam and money is tight? Ask us — we comp students who need it.
Launch pricing — the first cohort helps set the real numbers.
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FAQ
Questions, answered.
Something not here? Write to us and a person answers: support@getcorollary.app.
About the tutor
Is this a real tutor or a chatbot wrapper?
Cora is an AI, built on a large language model, and she says so. What is built around the model is the point: a handwriting canvas, not a chat box. You write your work by hand; the tutor reads the ink, marks it in place, and answers beside your marks. Around that sit concept drills, study plans built from your own textbook, LaTeX write-ups, and spaced review. Chat is one surface of the tutor, not the product. See the same problem put to a chatbot and to Corollary.
How is this different from ChatGPT?
A general chatbot is built to finish your problem, and it does that well. Corollary is built so you can finish it. Cora reads your handwriting, shows the method, marks the line that went wrong, and gives you the next step to try. Around that sits what a chatbot does not keep: a plan paced to your date, review cards made from your misses, and grading against a rubric. See one model answer the same question both ways.
Will my teacher see this as cheating?
That is your teacher's call, so ask them. Corollary is built for learning, not for handing in. Cora gives you the next step, not the finished answer, and you write the work yourself. If your class does not allow AI help on an assignment, use Corollary to study for it, not to do it.
What subjects does it cover?
Math, chemistry, physics, biology, economics and foreign languages, plus a general mode for everything else. Each one has its own tutor with its own voice and notation — chemistry gets mhchem and mechanism diagrams, languages get stroke-order handwriting on the web — and every subject gets the same canvas, drills, plans, and spaced review.
Do I need the AP part?
No. Test Prep is an optional add-on for people sitting an exam — 13 AP courses plus the SAT and ACT. You pay for it once and keep it. The tutor is a complete product without it, and Base never includes or requires it. If you're not taking one of those tests, ignore that section entirely.
What does the free trial include?
Everything, for 14 days: every subject, the canvas, drills, plans, and review, plus Test Prep if you want to see that too. No card to start. When it ends, nothing is charged, and your work stays yours: your boards, notes and flashcard review, and your 4 newest notebooks to keep writing in. Cora needs a plan after that. Base is $20 a month. Test Prep is a one-time add-on on top of it: AP prep is $20 and SAT/ACT prep is $15, paid once.
Where does it work?
It is available for iPhone and iPad, and coming soon to Android and the web. There is one app for iPad and iPhone. The canvas is built for the Pencil first: low-latency ink, finger panning, and grading that reads your actual handwriting. The iPhone is for the minutes in between: chat with Cora, review your cards, snap a photo of homework and see your plans. Boards open on an iPad, and on a computer once the web version is out.
Is the AP rubric the real one?
The practice questions are original — we don't use College Board's copyrighted exam items. They're scored with reader-style, point-by-point rubrics built from the public Course and Exam Description, so each point maps to the kind of point a reader awards, with the reason it was earned or lost.
What happens to my price after the exam?
Nothing changes. Base is $20 a month, or $200 a year, and you can cancel it anytime. Test Prep is paid once: AP prep is $20, SAT/ACT prep is $15, and both are $35. Nothing renews after test day. You keep it for as long as you have a Base plan, and if you cancel Base it waits for you.
For parents
Will it just do my child's homework for them?
Not by default. Cora starts with a question or a hint, not the answer. When a student is stuck she gives the next question rather than the next line. A student can switch her to a mode that shows the worked steps, so this is a default, not a lock. Work is done by hand on the canvas, so the student writes the steps and Cora marks them. In a study plan, a step counts as learned only once the student shows it on their own: in the session, in marked handwritten work, or in a short exit ticket taken without help. A question they miss comes back in review.
How old do you have to be?
13 and over. Date of birth is asked when an account is made and one is not created below that age. Accounts we know belong to a minor get extra protections — a periodic reminder to take a break, a standing reminder that Cora is a machine, and no per-user behavioral analytics. Read the safety page.
What happens if my child types something worrying?
Cora stops tutoring, says plainly that she is a machine and cannot be what they need, and points them to a crisis line and to an adult they trust. Separately, and not depending on the model getting it right, a rule puts the crisis numbers on screen before the reply is even written. It is not a monitoring service and it does not alert anyone — the published protocol says exactly what it does and does not do. Read the crisis protocol.
What do you do with my child's work and data?
The work is theirs. We don't sell data, there are no advertising or third-party tracking SDKs in the app or on this site, and the only cookie the site sets is the one that keeps you signed in. Accounts belonging to a minor are excluded from per-user analytics entirely — that usage is counted in aggregate and cannot be traced back to a person. An account can be deleted from Settings, which removes the work with it. Read the privacy policy.
How do I cancel?
From account settings, at any time, without emailing anyone — it opens the billing portal where you can cancel, change your card or download an invoice. You keep access until the period you've paid for ends, whether that is a month or a year. Read the terms.
Corollary · iPad, iPhone, web
Do the work by hand. Cora shows you the next step.
“Bring me the page you’re stuck on. I’ll be here.”
Free for 14 days. No card.
