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Leon

Privacy policy

Effective 11 October 2026

Leon is a Chrome extension and website that blends new vocabulary into what you read and helps you practise it. This policy explains what we collect, why, who processes it on our behalf, and how you can export or delete it. Questions: support@languageleon.com.

Your account

When you sign up we store your email address, a password hash and, if you add one, a passkey. Your account also holds the languages, topics and vocabulary lists you choose, the words you meet and save, your practice results and your settings.

Reading with the extension

  • The extension only reads pages on sites you allow. It sends eligible article text, your selected topics or vocabulary and your language settings to Leon so we can choose and translate words. It never sends forms, editable text or page HTML.
  • We translate that text with OpenAI. We ask OpenAI not to store it for later use; OpenAI's own retention policies still apply. Leon does not keep full page addresses or article text.
  • Each translation request includes a fingerprint (a one-way digest) of the page address, which we re-key with an account secret before storing it, so it cannot be turned back into the address.
  • YouTube captions and local PDFs are read on your device. Only the text you translate is sent; PDF files, filenames and document details are not saved.
  • Vocabulary lists you import are uploaded to your account so they can be prepared and practised. Sites you turn off are saved to your account as site names.

Save sites

Save sites is on by default. For words you learn, it keeps the site name, plus the article title (up to 300 characters) and a short excerpt (up to 400 characters) so you can see where you met a word. Titles and excerpts are deleted after 30 days by default. Turn Save sites off in Settings to stop saving them, or delete your history at any time.

Website analytics

We use PostHog to understand how Leon is used. On the website it records page views (the page path only, never query strings) and a few account events, such as finishing setup, completing a practice session, adding vocabulary and starting checkout. These are linked to your account ID, not your email. IP addresses are discarded, and we never record clicks, keystrokes or screen recordings. If your browser sends Do Not Track or Global Privacy Control, page views are not recorded. The extension sends nothing to PostHog.

Payments and email

Stripe processes subscriptions; card details go to Stripe, not to Leon. We keep your plan and subscription status. Verification codes and password-reset links are sent through our email provider.

Operational records

To run the service and enforce plan limits we keep request IDs, pseudonymous fingerprints, counts and status codes, never the text you read or the translations. Detailed usage records are deleted after 90 days and monthly totals after 13 months.

Who processes your data

  • Vercel hosts the website and API.
  • Supabase stores your account and learning data.
  • OpenAI translates reading text.
  • Stripe processes payments.
  • PostHog provides website analytics.
  • Our email provider delivers account emails.

We do not sell your data, use it for advertising, or use your reading to train AI models. Data from the extension is used only to provide Leon's translation and learning features.

Your choices

  • Export everything in your account from Account settings.
  • Delete your account there too. Deletion removes your account, vocabulary, history and usage records together, cancels any subscription and deletes your Stripe customer record. Stripe keeps the payment records it is required to retain. To remove analytics data linked to your account, email us.
  • Disconnect the extension from Account settings, or remove it from Chrome. Website access can be withdrawn in Chrome at any time.

Children

Leon is not directed at children under 13.

Changes

If we change this policy we will update this page and its effective date. For anything else, see Support.