Privacy Policy
Last updated: October 23, 2026
This page explains what math4ai.org collects, why, and who else sees it. We collect only what the site needs to work, and we don't sell personal information.
Your account
- Email address and display name, and a password (stored only as a secure hash) or your Google sign-in.
- Used to sign you in, to tell you about your membership and orders, and to answer you.
Membership (redeeming your receipt)
- The receipt you upload, your email, and any notes. Receipts are stored privately and are seen only by the author to verify your purchase; they are never published.
- Technical details of each submission: IP address, browser (user agent), the page you came from, and a fingerprint of the file. We use these only to stop abuse of the form (spam, repeated attempts).
Member materials
When you watch a premium video we record your account, the chapter, the time, your IP address and browser. This protects the materials from redistribution; see the copyright notice.
Printed copies
- For an order we keep your name, shipping address, phone number and email.
- Lulu (our printer) receives your name, address, phone and email to print and ship the book.
- PayPal handles the payment. We never see your card or bank details; PayPal tells us whether the payment went through.
- Carriers and customs in your country may receive what they need to deliver the parcel.
Cookies and analytics
- Necessary cookies keep you signed in and protect forms (session and CSRF cookies).
- Google Analytics counts visits and pages to show us what readers use. It sets its own cookies; see how Google uses data from sites that use its services, and you can block it with the Google Analytics opt-out or your browser's settings.
- Your browser may remember small preferences (for example, which Studio panes you show) in its own storage; that never leaves your device.
Embedded videos
Lecture videos play from our video site, share.deskpai.com. If a video comes from YouTube or Vimeo, that service may set its own cookies when you play it.
How long we keep it
Account and membership records are kept while your account exists. Order records are kept as long as tax and accounting rules require. Abuse-prevention logs are kept only as long as they are useful for that.
Your choices
You can ask for a copy of your data, or ask us to correct or delete it (we keep only what the law requires us to keep, such as order records). Email xuanxinjushi@gmail.com.