Privacy

Mathend is built so that the interesting data never reaches us. This page describes exactly what does.

Your documents stay on your device

Notes, derivations and documents are stored in local storage on your own machine. There is no server-side database of your documents, no sync service, and no backup we hold. If you uninstall the app or clear its storage, that data is gone — we cannot recover it for you.

The one exception is deliberate: when you send a request to an AI model, the part of the document the agent needs is transmitted to that model provider in order to answer. Nothing is sent until you ask for it.

If you bring your own API key

With your own key, requests go from your machine directly to the provider you chose — Anthropic, OpenAI, Google, Zhipu, DeepSeek, xAI, Mistral, Groq, OpenRouter or GitHub Copilot. That traffic does not pass through our servers and we never see your key or your prompts. The provider’s own privacy policy governs what they do with the request.

If you use the hosted agent

The hosted agent routes your request through our gateway to OpenRouter using our key. To bill you, we record the model used, the input and output token counts, the upstream cost and the resulting charge. We do not store the content of the prompt or the completion in that ledger.

Account data

An account is only required to buy credits. When you create one we store your email address, your name, and — if you sign in with Google — the profile image and identifiers Google returns. Sessions record an IP address and browser user agent so that a session can be recognised and revoked.

Payments

Credit purchases are processed by Polar, which acts as merchant of record. Card details are entered on Polar’s systems and are never sent to or stored by us. We receive the order confirmation needed to credit your balance.

Email

Transactional email — address verification and password resets — is sent through Resend. We do not send marketing email.

Analytics

This website uses Vercel Analytics, which counts page views without cookies and without building a cross-site profile of visitors. The editor itself contains no analytics.

Retention and deletion

Account records, the credit ledger and payment records are kept for as long as the account exists, and afterwards only where a financial record has to be retained. To delete your account and its data, email support@mathend.com.

Changes

If this policy changes materially, the date at the top of this page changes with it. See also our terms of service.