Privacy policy

Last updated 9 October 2026

Cestra exists so that your software and your data are yours. This policy says what we collect, why, where it goes and how you stay in control. It is written to meet the General Data Protection Regulation (GDPR) and to be understood without a lawyer.

The short version

We collect what we need to run your account and your apps, and nothing for advertising. No ad networks, no cross-site tracking, no selling data.
Your apps run in your own database. What people enter in your app is yours to control, and we only process it to run the app for you.
Usage insights about your apps go to you, the owner. They never go to third parties.
Your descriptions and app content are sent to AI models to build and change apps, under contracts that forbid the provider from using them to train models.
You can see, export, correct and delete your data at any time. People using your apps can remove their access and data themselves.

The full text below is what applies. The summary is here to make it easier to read.

1Who is responsible

[Cestra legal entity], registered at [address], is the controller for the personal data described in this policy, except for data inside apps that other users publish, which is covered in the section on apps you use.

Contact for anything about your data: info@cestra.ai, or by post at the address above. [If a data protection officer or EU representative is appointed, add their contact here.]

2Two roles: your account, and apps you use

Cestra handles personal data in two different roles, and your rights depend on which one applies.

For your account, the waitlist, the studio and this website, Cestra is the controller. We decide what is collected and why, and this policy applies in full.
For data inside an app published by another user, that user (the owner) is the controller and Cestra is the processor. The app runs in the owner’s database, and we only process what is in it on the owner’s instructions. The owner is responsible for telling you what the app does with your data.

When you publish an app that other people use, you take on the owner role for the data they enter, and we process it for you under the data processing terms in the terms of service.

3What we collect

Waitlist. The email address you enter on this website, the time you entered it, and whether an invite has been sent. Nothing else.

Account. Your name, email address, password (stored only as a hash) and the one-time codes we send you to sign in or reset a password. We also keep the time of your sign-ins and the browser and device they came from, for security.

Building. The descriptions you write, your messages in a session, and everything Cestra produces from them: screens, code, database structure, docs and versions. Design systems you create or pick are stored with your account.

App data. The records you and your invited people enter in your apps. Each app has its own database that belongs to the app’s owner.

Access and sharing. Who you invite to an app, their email and role, when access expires, requests to join, and the consent each person gave before opening an app.

AI usage. For each AI action inside an app: which app, which person, how many tokens, when, and who paid. This is what the owner sees as usage insights.

Technical data. IP address, browser type, device type, pages requested and error logs, kept in server logs for security and troubleshooting.

Messages. What you send us by email or through “Report this app”.

We do not collect payment details. Cestra does not take card payments. If that changes, we will update this policy before asking for anything.

4Why we use it, and the legal basis

GDPR requires a legal basis for each use. These are ours.

To run your account and your apps, serve them at their links, sign you in, and deliver what you asked for: performance of a contract (Article 6(1)(b)).
To send you your waitlist invite and messages about the beta that affect your use of it: steps taken at your request before a contract, and our legitimate interest in running the beta (Article 6(1)(b) and (f)). We do not send marketing email without your consent.
To show owners who used their app and what AI actions cost: performance of the contract with the owner, and our legitimate interest in making token allowances transparent (Article 6(1)(b) and (f)).
To keep the service secure, detect abuse and fix errors: our legitimate interest in a service that works and is safe for everyone (Article 6(1)(f)).
To improve Cestra, using aggregated numbers that do not identify people: legitimate interest (Article 6(1)(f)).
To keep records and respond to lawful requests: legal obligation (Article 6(1)(c)).

We do not profile you, make automated decisions with legal effects about you, or use your data for advertising.

5AI models

To build and change apps, Cestra sends your descriptions, session messages and the relevant parts of your app’s code and structure to AI model providers. When an app includes an AI feature, the content that feature works on is sent in the same way when someone uses it.

Providers act as our processors under written contracts. They may not use what we send for their own purposes and may not train models on it. We choose providers that delete inputs and outputs after a short retention period, and we list the current providers at [link to subprocessor list].

AI output can be wrong. Nothing an app or the studio produces should be treated as professional advice.

6Usage insights for owners

If you own an app, you can see who ran AI actions in it, how many, how many tokens they used, who paid, and your sessions building it. This is shown so you know where your allowance goes and who is using your app.

If you use someone else’s app, the owner sees your name, your email, your role, and your AI usage in that app. They do not see your activity in other apps, your sessions, or anything about your account beyond that. Cestra never passes usage insights to advertisers or data brokers.

8Where data is stored

Your account and your apps are hosted in [region, e.g. the European Union]. Some processors, including AI model providers, may process data in the United States or elsewhere. Where data leaves the European Economic Area, we rely on an adequacy decision or the European Commission’s standard contractual clauses, plus technical measures such as encryption in transit and at rest.

9How long we keep it

Waitlist email: until you receive an invite and create an account, or until you ask to be removed, and in any case no longer than 24 months after joining the list.
Account data: for as long as your account exists, then deleted within 30 days of closure.
Apps and app data: for as long as the app exists. Deleting an app deletes its database. Backups are overwritten within 30 days.
Access records and consents: for as long as the related access exists, plus 12 months, so that we can show what was agreed.
AI usage records: 13 months, so that owners can review a full year.
Server logs: 90 days, unless needed for an ongoing security investigation.
Support messages and reports: 24 months after the last reply.

10Your rights

Under GDPR you can ask us to:

tell you what data we hold about you and give you a copy (access)
correct data that is wrong (rectification)
delete your data (erasure), which closing your account does for account data
limit what we do with it while a question is settled (restriction)
give you your data in a machine-readable form, or send it to someone else (portability). Exporting an app gives you its code, database and docs
stop processing based on legitimate interests (objection)
withdraw consent where consent is the basis, without affecting what happened before

Most of this you can do yourself: edit your account, export or delete apps, and, for apps you have joined, remove your access and your data from Account → Apps you’ve joined. For anything else, email info@cestra.ai. We answer within one month, and tell you if we need longer.

For data inside another user’s app, send your request to the app’s owner. If you cannot reach them or they do not answer, contact us and we will help, including by removing your data where we are able to.

You can complain to a data protection authority. In the EU you can choose the authority in the country where you live or work. Ours is [supervisory authority of the country of establishment].

11Cookies and browser storage

This website sets no cookies and uses no analytics scripts.

The studio and published apps use browser storage to keep you signed in and to remember preferences such as the apps you pinned, the consent you gave to an app, and whether you turned on “Use my own tokens”. These are needed for the service to work and are not used to track you across other websites. Clearing your browser storage signs you out.

12Security

Data is encrypted in transit and at rest. Passwords are stored as salted hashes. Each app’s database is separate, and what an app can reach outside Cestra is limited to the hosts its owner lists. Access to production systems is restricted to the people who need it, and logged.

If a breach puts your rights at risk, we will tell you and the relevant authority without undue delay, as GDPR requires.

13Children

Cestra is not for anyone under 16. We do not knowingly collect data from children. If you think a child has created an account, tell us and we will delete it.

14Changes to this policy

When this policy changes in a way that matters, we email account holders before the change takes effect and update the date at the top of this page. Earlier versions are available on request.

Questions: info@cestra.ai.