This policy explains what Lemma stores when you use the site, why, and how you can delete it. Lemma is run by Thomas Zheleznyak, a sole proprietor, 711 Utterback Store Road, Great Falls, VA 22066, USA ("we", "us"), who is responsible for your data. The short version: your notes and lessons are private to your account, we use them only to run the service, and we never sell your data.
Who can use Lemma
You must be 13 or older to create an account, and you confirm this when you sign up. We don't knowingly collect information from children under 13. If you believe a child under 13 has an account, contact us at support@lemmalessons.com and we will delete it.
What we store
- Your account: your email address, the date you confirmed you are 13 or older, and (if you sign in with Google) the name and profile picture Google shares with us.
- Your sign-up answer: how you heard about us.
- Your uploaded notes: the text, photos and PDFs you upload, plus any note you add about what to focus on. Uploaded files are kept only until your lesson is made, then deleted.
- Your lessons: each lesson made from your notes, kept in your library until you delete it.
- Your progress: what you've revealed, answered and scored inside each lesson, so you can pick up where you left off.
- Your credit history: credits you received, used, or got back.
- Mistake reports: anything you send with the "Report a mistake" button.
- "Get notified" list: your email, if you ask to hear when payments open.
- Payments: what was bought, when, for how much, and the email of whoever paid (a parent, for example). Purchases are sold through Link, the checkout service of Stripe, as the merchant of record: Link collects the buyer's name, email, billing address and payment details itself, under its own privacy policy, and card details never reach our servers (see Link's privacy policy and Stripe's privacy policy). We keep our payment records with your account until you delete it; Stripe keeps its own records of each payment for as long as tax and anti-fraud laws require, even after that.
- Basic technical data: like most websites, our servers see your IP address and browser type. We use your IP address briefly, in memory only, to prevent abuse (for example, too many sign-in emails from one place); we don't store it. Our host keeps the site's technical logs (errors and which pages were asked for, never your notes) for up to 30 days.
How your notes are turned into a lesson
Lessons are written by an AI model. To make your lesson, your notes and request are sent to our AI provider, Anthropic, which processes them for that one job and sends the lesson back. Under the way we use Anthropic's service, your notes aren't used to train AI models, and Anthropic deletes them within 30 days (see Anthropic's commercial terms).
Other companies help us run the site, and only handle your data to provide those services to us: Railway (hosting, our database and stored files), Anthropic (writing lessons), Stripe and its Link checkout (payments; Link is the merchant of record), Resend (sending email), and Google (only if you sign in with Google).
Inside a lesson
Lessons run in a locked-down frame that can't read your account or cookies. To display math and fonts, a lesson may load files from jsDelivr (cdn.jsdelivr.net) and Google Fonts. Those services receive your IP address and browser details when the files load, the same as on any website that uses them.
Cookies
We use one cookie to keep you signed in. We don't use advertising or tracking cookies.
What we never do
- We never sell your data.
- We don't show ads, and we don't share your notes or lessons with other users.
- We only share data with the service providers above, or when the law requires it.
Deleting your data
You can delete any lesson from your library. To delete everything, go to the Account page and choose "Delete my account and data". That permanently removes your account, notes, lessons, progress, credit history, mistake reports and any "get notified" signup tied to your account. We keep only a one-way, scrambled fingerprint of your email address (not the address itself), so the free sign-up credits aren't given twice to the same address. Deleted data can stay in our database backups for up to 90 days, until those backups are replaced.
To ask what data we hold about you, to get a copy, or to have it corrected or deleted, contact us at support@lemmalessons.com from the email address on your account. Depending on where you live (for example in the UK, the EU or some US states), the law may give you these rights and others, such as objecting to how we use your data; we honor them, and you can also complain to your local data protection authority. We use your data to provide the service you asked for, to keep it safe, and to meet legal duties.
Lemma is run from the United States, so your data is stored and processed there and by the providers listed above.
Changes to this policy
If we make important changes, we'll update this page and the date at the top, and tell you on the site or by email.
Contact
Questions about privacy? Email support@lemmalessons.com, or write to Thomas Zheleznyak, 711 Utterback Store Road, Great Falls, VA 22066, USA.