Privacy Policy

In effect since 30 July 2026

MathDaily hands you one piece of mathematics a day and keeps a record of what you have worked through, so the record can be shown back to you as a tree. That record is the product, so this page is mostly about it: what is in it, where it lives, who else can reach it, and how to destroy it.

Everything below describes the site as it is deployed today, not a plan. Where a sentence says that something does not exist here, it is a statement about this deployment — and the section on who else can see your data is computed from what this deployment is actually connected to, so it cannot fall behind a change nobody remembered to write down.

What we store

Nothing on this list is inferred about you, bought from anyone, or enriched from another source. Every item is something you typed here or something you did here.

The waiting list: if you submit your address on the front page, we store that address and which language the page was in. That is the whole row — no IP address, no browser fingerprint, no referrer.
Your account: the email address you signed up with, the display name you chose if you gave one, and — if you signed in through another account — the avatar image URL that account handed us. A password is stored only as a hash, so we cannot read it back and cannot tell you what it was.
Your session: while you are signed in there is one row holding a random session token, when it expires, and the IP address and browser user-agent string the sign-in came from. Those last two are recorded so that one session can be told apart from another.
Your learning record: which concepts you have met, how strong each one is right now, when each is next due, which questions you answered, whether each answer was right, how many hints you opened, and how many times you have used each kind of mathematical thinking.
Your sessions: for each daily session, its date, its position within that day, whether it is still open, which concept was new in it, and the internal state of the workflow that ran it — which is what lets a session you closed halfway be picked up again.
The daily email, and only if you switch it on: that it is on, which language to write it in, your timezone offset so it arrives in the morning where you are, a random unsubscribe token, and the date of the last message we sent you.

What we do not collect

This list is short because the site is small. It is here because the opposite claim is the one most sites make without checking — and because this page made it too, until today.

No analytics, of any kind. No Google Analytics, no product-analytics SDK, no tracking pixel, no heatmap, no session recording. The pages load no script, no font and no image from any other host: everything your browser fetches here comes from mathdaily.org.
No advertising, no advertising identifiers, and nothing sold, rented or shared for marketing. There is no advertising business here that would want it.
No payment information. Nothing on MathDaily is for sale and no payment provider is connected to it, so there is no card number, no billing address and no purchase history to hold.
No phone number. Neither the sign-up nor the sign-in form asks for one, and the phone sign-in path is switched off in this deployment.
No profile of you anywhere else. We do not know what you do on other sites and have no way to find out.

Who else can see it

A short list, and it is computed rather than typed: this page can only name a party that this deployment is actually connected to, and it names every one that it is. That is a property of how the page is built, not a promise we are making about proofreading — if something is missing from the list below, the connection does not exist here.

Cloudflare. The site runs on Cloudflare's network, the database is Cloudflare D1, and the daily email is handed to Cloudflare to deliver. So Cloudflare processes every request you make here, stores on our behalf everything listed above, and keeps request logs that we use for debugging.
Google, and only if you choose "Continue with Google" on the sign-in page. Google then knows that you signed in to MathDaily. From Google we receive your email address, your display name and an avatar URL, and nothing else. Signing up with an email address and a password involves Google not at all.
Cloudflare Workers AI, when you ask why an answer was wrong: the question, its options, the answer you gave, the authored hints and the worked example are sent to a model running on the same Cloudflare account as the rest of this site, so that it can write that explanation. No further company is involved — Cloudflare is already named above — and the reply is not written to the database; nothing you type is sent to a model at any other moment.

Cookies, and what stays in your browser

There is no cookie banner because there is nothing to consent to. None of the following are used to follow you, and two of them are not cookies at all.

A session cookie, set when you sign in. Without it you cannot stay signed in; it is the only cookie the site actually needs.
A language cookie, written only if you use the language switcher, so your next visit opens in the language you picked.
Your light-or-dark choice, kept in your browser's local storage. It never reaches our server.
Nothing else. No advertising cookie, no analytics cookie, and no cookie set by another company.

How long we keep it, and what deleting your account really deletes

Your account and your learning record stay until you delete the account. Deleting it removes the account, its sign-in methods, its sessions, your tree, your daily sessions and every answer in them, your thinking-tag counts and your email preference — each of those is stored against your account and goes in the same operation.

One thing does not go with it, and we would rather tell you than let you assume otherwise. Each session also stores the internal state of the workflow that ran it, and those rows are keyed by the session rather than by your account, so today the deletion does not reach them. They hold what the session held — the concept you were shown and what you answered — and they still carry the internal account id they were created for, which after deletion no longer resolves to an email address here. We treat that as a defect to fix, not as a retention policy, and this paragraph will go when the defect does.

A waiting-list address is not part of an account, so deleting an account does not remove it. It stays until the list has served its purpose or until you ask us to remove it. Sessions expire on their own.

What you can do about all of this

The first two you can do yourself, right now, without asking us and without waiting for us.

Delete everything: Account management on your dashboard deletes the account and the record attached to it. There is no cooling-off period and no way for us to undo it, which is the point of it.
Stop the daily email: every message carries an unsubscribe link that works without signing in — one click, and nothing else about your account changes.
Ask for a copy, a correction or a deletion by mail: write to the address below and a person will answer. Depending on where you live you may have a legal right to any of these; we would do them anyway.

Changes to this page

When what the software does changes, this page changes with it and the date at the top moves. We will not quietly widen it: anything new that gets collected is a new line in the list above, and that list is deliberately short enough to re-read in one sitting so that a new line is visible.

Reaching us

One address, and a person reads it:

hello@mathdaily.org

This page is published in English and in Chinese. Both are written and maintained by hand and are meant to say the same thing. If they ever differ, the English version is the one that governs.