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QDD terms of service

Last updated: September 4, 2026

These terms are the agreement between you and CrumbQuest LLC, a New Mexico limited liability company, 1209 Mountain Road Pl NE, Albuquerque, NM 87110, USA, covering the QDD (青豆丁) app and the website at qingdouding.com. Using either means you accept them. If you do not, don’t use them.

How we handle information is a separate document: the privacy policy.

Who can use QDD

QDD is for tutors keeping their own teaching records. You need to be 18 or older, able to enter a contract, and a human — accounts registered by scripts or bots are not allowed. One person, one account: QDD has no way to invite an assistant, share a student, or hand an account to someone else.

Keep your sign-in to yourself. Passwords are stored only as a hash, so we never see the original; if you turn on Face ID or fingerprint unlock, the credential lives in your device’s own keychain. Only one device per account can have it: once it is set up, a second device is not offered it and signs in with the password instead, and the first device is unaffected. The credential is also stored so that iOS destroys it the moment that device’s own biometric set changes — a phone that is sold, reset, or has another fingerprint added loses it outright, without us doing anything. Tell us straight away if you think someone else has got into your account. What happens under your account is your responsibility.

What QDD is, and what it is not

QDD is a record-keeping tool. It holds your schedule, your lesson history, and your record of what has been paid and what is owed.

No money moves through QDD. It is not a payment processor, a bank, or a payment service of any kind, and it is not connected to one. When you mark a lesson paid, you are writing down something that happened somewhere else — in cash, by Zelle, by check. If a payment never arrives, that is between you and the family, and QDD has no part in it and cannot recover it.

QDD is also not accounting, tax or legal advice. The numbers it shows you are arithmetic on what you entered. Before you rely on them for a tax return or anything else that matters, check them, and talk to someone qualified.

Your records are yours, and so is the responsibility for them

Everything about a student or family in QDD is there because you typed it in. That means:

Please do not put things in QDD that it was never built to protect — government ID numbers, card or bank details, medical records. It has no field that asks for them. But notes are free text and support tickets accept image and PDF uploads, so technically you could. Please don’t.

Where your data lives

QDD is run by CrumbQuest LLC in the United States, and your records and your students’ records are stored in the United States. To actually run the service we rely on these providers, and your data passes through them:

Apple is not on that list: it distributes the app, and no student record, lesson or parent address ever reaches it. The App Store section below covers what does apply if you installed it that way.

There is nobody else. The app carries no analytics code and no third-party error reporting, and even its fonts are served from our own servers.

If you teach in mainland China, read this together with the consent point above. The student records you enter are transferred out of China and stored in the United States. Under China’s Personal Information Protection Law, the personal information of a child under 14 is sensitive personal information and needs a guardian’s consent to process at all; sending it abroad additionally requires telling the family who the overseas recipient is, why, and what is being stored — and getting separate consent for that specifically. Where the student is an adult, that consent is theirs to give, not a guardian’s.

So when you explain this to a family — or to the student directly, if they are an adult — say plainly that the records will be held in the United States by CrumbQuest LLC, and get their agreement to that on its own rather than folded in with everything else. A family can see, correct or delete their records through you, or by writing directly to hello@qingdouding.com.

Who can see your records

Normally, only you.

But leaving it there would not be honest. There are very few of us, and to help with a problem you have raised, a small number of us can open your account and see what you see — including the messages sent to parents on your behalf. That does not need your say-so first, but it is not casual either:

If we change something while we are in there, your own activity history shows that entry marked “By support”. If we only look — open the account, read the activity list, pull up an archived email — that is recorded on our side only, and you will not see it. Those are two different things, so we are not going to blur them.

Beyond that, we do not read your records out of curiosity, we do not use them for advertising, and we do not use them to train models. Nothing in QDD sends your content to an AI provider today — if that ever changes, it will be written here first.

Email QDD sends for you

QDD can email parents on your behalf: statements, payment confirmations, lesson reminders, payment reminders, schedule changes. Those messages go out under your name, and they are your messages.

There is one more that you do not send deliberately. The first time you enter a parent’s email address, QDD sends that address a notice explaining that you have added them and where to click if it is not their address. Until that notice has gone out, QDD will not send anything else to it.

So only enter an address for a family you actually teach and who expects to hear from you. QDD is not a mailing-list tool, and using it to send bulk or unsolicited email is not allowed. We may stop sending to an address that bounces, gets reported as spam, or uses the “this isn’t my email” link, and we may stop sending for an account that is generating complaints.

The parent’s side of it

Parents do not register and cannot open the app. But every message they get carries a link to a page we host, where they can choose which kinds of message they receive, or click “this isn’t my email”.

What a parent chooses there overrides your settings in the app. If you have a category switched on and the parent has switched it off, it does not go — and those switches are read-only on your side, so you cannot put them back. Two of them, schedule changes and payment confirmations, are parent-only: you have no switch for those at all. The one message that cannot be turned off is the notice described above, because it is the message that carries the opt-out link. That is deliberate: the person receiving these messages never agreed to these terms, so the one thing we owe them is a way to stop.

“This isn’t my email” is recorded against that parent on that family, not against the email address. If the same address is also on another family record — another teacher, or a separate household you set up for a sibling — that record is unaffected and keeps sending.

What you send us

You can open a support ticket in the app, attach images, PDFs or spreadsheets, and reply by email — your reply is written back into the same ticket. That content enters the system and we read it, so the same rule applies: no ID numbers, card details or medical records in a ticket.

If you tell us what QDD should add or change, we can go and build it without asking you again and without owing you anything for it. You lose nothing by making a suggestion; this clause just means we can act on one.

Things you may not do

If one account’s usage runs far enough above normal to affect everyone else, we may throttle it. Unless it is urgent, we will contact you first.

What it costs

QDD is free right now. That is not a promise that it is free forever.

If we introduce paid plans, we will say so in advance, and we will not start charging an existing account without asking first. Nothing here lets us bill you for something you didn’t agree to.

Who owns what

Your records are yours. We do not claim ownership of anything you put into QDD.

To actually run the service we need your permission to do the obvious things with it: store it, back it up, process it, show it back to you, and send the messages you ask us to send. That permission is limited to operating QDD for you, and it ends when your data is deleted — the off-site backups being the one exception, described under “Ending it” below. We do not sell your records, and we do not use them to advertise to anyone.

The app itself — the software, the name, the design — stays ours.

Taking your records with you

Any time, without asking us. Settings exports your students, lessons, payments and families as an Excel workbook, covering both profiles, with a sheet showing which lessons each payment covered and another listing your saved locations. Statements and family records export separately as PDFs. You run the export from your main profile. This is not something you get as a consolation when you leave; it is there the whole time.

Worth saying what it does not cover: families you have marked inactive, your activity history, the archive of messages and statements already sent to parents, support tickets and their attachments, and your account-level notification and billing defaults are not in it. It is a copy of the records listed above, not a complete copy of your account.

Ending it

You can delete your account from inside the app whenever you like. It is deactivated immediately and permanently erased after a 30-day grace period, which is there so an accidental deletion can be undone. Deleting your account also deletes the student and family records you entered. The privacy policy has the detail.

Two things need saying plainly. First, we back up each tutor’s data to Microsoft OneDrive nightly, and an account stays in those backups throughout the 30-day grace period — so the last backup containing your records is dated around the day your account is purged. Each dated backup is kept for up to 180 days, then deleted. Deleted files then sit in Microsoft’s own recycle bin for a further 30 days before they are gone. Second, the access log described under “Who can see your records” is kept. It records what we did.

We can suspend or close an account that is breaking these terms, or being used in a way that puts other people or the service at risk. Unless the situation makes it impossible, we will tell you why and give you a chance to get your records out first.

If we ever shut QDD down, we will give you reasonable notice and a way to export your data before it goes.

What we do and don’t promise

We work to keep QDD running and correct, and we would rather hear about a problem than not — write to us. Like all software it has bugs; we work through the ones reported to us in order of how much they matter, but we do not promise every one gets fixed.

But QDD is provided as is, without warranties of any kind, express or implied, including any implied warranty of merchantability, fitness for a particular purpose, or non-infringement. We do not promise it will be uninterrupted, error-free, or that it will never lose data. There is no guaranteed uptime.

Keep your own copy of anything you cannot afford to lose. This is a free tool run by a very small company, and that is honest advice rather than fine print.

Finding a security problem

If you find a vulnerability, write to hello@qingdouding.com before making it public. We will reply. Poking at your own account’s data to confirm a problem is fine; going through someone else’s is not.

Limits on what we owe you

To the fullest extent the law allows, we are not liable for indirect, incidental, special or consequential damages, or for lost profits, lost income, lost data, or payments a family never made to you.

For everything else, our total liability to you is capped at the greater of the amount you paid us in the twelve months before the claim, or US$50.

Some places do not allow these limits. Where that is true, they apply only as far as that jurisdiction allows, and nothing here takes away consumer rights you have by law.

If your use of QDD causes someone else a problem

If a claim is brought against us because of what you put into QDD, how you used it, or messages QDD sent on your behalf, you agree to cover our reasonable costs in dealing with it.

Changes to these terms

We may update these terms. If a change matters, we will update the date at the top and tell you in the app or by email. Continuing to use QDD after a change means you accept it; if you don’t, you can delete your account.

Which law applies

These terms are governed by the laws of the State of New Mexico, USA, without regard to its conflict-of-laws rules, and disputes belong to the state or federal courts sitting in New Mexico. If you are a consumer somewhere with stronger local protections, this does not take those away.

If any part of these terms turns out to be unenforceable, the rest still stands.

If you got QDD from the App Store

Apple requires a few things be said plainly, and they are true:

Contact

Questions, complaints, or claims about QDD come to us here:

hello@qingdouding.com
CrumbQuest LLC, 1209 Mountain Road Pl NE, Albuquerque, NM 87110, USA


QDD · Lesson and payment tracking for one-on-one piano teachers

QDD is a product of CrumbQuest LLC · 1209 Mountain Road Pl NE, Albuquerque, NM 87110, USA