Sapwood
Start with something you’re curious about. Get a clear course with bite-sized lessons, practice and progress you can see.
A variable is a letter, like x or y, that stands for a number we do not know yet. If x = 3, then x + 5 becomes 3 + 5, which equals 8.
A variable is best described as:
Choose an answer to try the lesson.
Pick a subject and a level, then let the course follow you.
Select the subject you want to learn and explore the available options.
Get structured lessons with clear texts, images and examples.
Reinforce the content with interactive quizzes and instant feedback.
Complete hands-on activities and track your continuous progress.
A complete platform for all your learning goals.
No ads, no tracking, no server. Just the course you chose and the progress you made.
Pick a subject, topic and level. Sapwood builds a course with clear explanations, practice activities and a final review.
Switch between English, Portuguese, Spanish, French, Italian and German without losing your place.
Your account, courses and progress stay in this browser. There is no Sapwood server and no analytics.
Once a course is opened, its lessons and progress keep working without a connection.
Create up to three courses for free. Pro lifts the course limit and unlocks every subject.
3 courses · Core subjects
One-time · Unlimited courses · All subjects
Everything you might want to know before you start.
Yes. You can create up to three courses and study every explanation level at no cost. Pro is normally a one-time purchase of $19.99 that lifts the course limit and unlocks every subject. During the launch offer you can claim Pro free on the Plans screen through 25 December 2026 and keep it for good; there is nothing to pay later.
Entirely in this browser, on this device. There is no Sapwood server, so your data stays on your device. If you use sign-in, it's local to this browser.
The interface is available in English, Portuguese, Spanish, French, Italian and German, and you can switch language at any time.
No. Sapwood runs in your browser. You can start learning right away — nothing to download or set up.
Once the page has loaded, your courses and progress work without a connection, because everything is stored locally.
Choose a subject, follow a steady path, and make what you learn part of you.
SapwoodTry one beginner lesson and a quick check. Nothing is saved, and you can head back whenever you like.
Choose an answer to see how feedback works.
A guided preview—from choosing a level to answering a lesson check. Nothing is saved.
Sapwood
Last updated: November 2026
Sapwood is a learning app that runs entirely in your browser. It has no accounts server, no database and no analytics - which shapes everything below.
Everything the app keeps about you - your display name and email, a hashed password, a hashed recovery key, your courses and everything attached to them (progress, scores, notes, highlights, favourites, study time, review schedule and last lesson), your preferences, language and notification settings, your site rating and, if you rate while signed out, a random anonymous rating ID - is stored in this browser, on this device, in the browser's local storage. Your signed-in session is kept there too. None of it is sent to a Sapwood server: there is no account server to send it to.
Because your data lives on your device, it stays here when you sign out, and is gone for good in this browser if you clear this site's data. Backups and a recovery key exist exactly to protect against that - see below.
We also keep your theme, language and notification preferences, your site rating and, for a rating made while signed out, a random anonymous ID used to recognise it on this browser. We do not collect analytics, location, or anything else beyond what the app needs to show you your own work.
From your settings you can download a backup file containing your account and progress, and restore it on any other device. You can choose to protect the file with a password (recommended if the file will sit in cloud storage). The recovery key, shown once when you create your account, is the only way to set a new password if you forget yours.
Fonts: the site serves its typefaces (Nunito and Outfit) from its own files. Your browser does not contact Google or any font CDN to load them, so no request leaves this site for typography.
Payments and the launch offer: during the launch offer, Pro is claimed free on the Plans screen and no payment details are collected. Outside that offer, buying Pro is handled by Stripe through a payment link when checkout is available. You are directed to Stripe's site to complete the purchase, and Sapwood never sees or stores your card details.
Lesson images: some lessons show photographs from Wikimedia Commons. Those images are loaded from Wikimedia's servers, so Wikimedia sees a request for the image file; no account data is sent. Each image links to its Commons page, where its author and licence are listed.
Because nothing leaves your device, deleting your data is fully in your hands: use your browser's "clear site data" for this site, or delete the export file if you made one. Removing all accounts and progress for Sapwood here removes every trace of you from the app - there is no account data held on a Sapwood server.
Questions about any of the above can be sent to our support address:
Sapwood offers interactive lessons to help you learn. Content is generated and provided for educational purposes and may contain errors - treat it as a study aid, not as professional advice.
The free tier allows three courses and includes Science, Mathematics, Languages & Literature, and Social Studies at every explanation level. During the launch offer, Pro can be claimed free on the Plans screen through 25 December 2026, and Pro claimed during the offer is kept permanently on that account at no charge. Outside the launch offer, Pro is a one-time purchase of $19.99 that removes the course limit and unlocks every subject for that account, with no subscription. Purchases are handled by Stripe when checkout is available and are final once completed.
Your account and progress are stored on your own device. You are responsible for keeping your password and recovery key safe; keep and protect your backups the same way you would any personal file.
The service is provided "as is", without warranties of any kind. To the extent permitted by law, Sapwood is not liable for any loss arising from use of the site.
Sapwood
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Sapwood
Start free. Upgrade whenever you want more.
Here's a summary of your learning journey and your courses.
Create your first course
No course in progress yet. Create your first course to get started!
Pick up your courses where you left off.
Keep learning every day!
No reviews due.
Manage, edit and track the courses you created.
Try one of these bundled examples. They are not added to your account, so they do not affect your progress or stats.
Questions from quizzes you passed, scheduled for another look.
Manage your profile and preferences.
Adjust how you want to use Sapwood.
Choose the language used across the whole website.
Create new courseFollow the steps below to generate a personalized course.
Here's the summary of your personalized course.
Choose a lesson to start learning.
Lesson description.
See your performance below.
You have successfully completed the course!
Choose a simple subject and course to get started. We'll create a quick 1-lesson demo for you to explore!