Legal document
Privacy policy
This document describes exactly what Cerno collects, what it doesn't, and where the data goes. It is short because there isn't much to say — and that's deliberate.
Last updated: 22 October 2026
1. Who is responsible
The data controller is Camille MISSIAEN, publisher of Cerno.
For any question about your data, write to contact@cerno-app.fr.
2. The principle
Cerno is designed to work without a server. The content you enter — tasks, habits, durations, focus sessions — stays stored in your browser and is never transmitted. We don't see it, because we don't receive it.
There is no user account, no password, no email address requested. You open the application and you write.
3. What the website collects
Nothing. The page you are reading uses no cookies, no trackers, no analytics tool. It contacts no outside service: the fonts are hosted with the site, precisely so that your IP address is not passed to a third party without your knowledge.
The hosting provider and your internet service provider keep technical logs, as for any website — that does not depend on us.
4. What the application stores on your device
The application uses your browser's local storage. This data never leaves your device and is accessible only to you.
| Key | Content |
|---|---|
| focus-app-tasks | Your tasks |
| focus-app-habits | Your habits and their history |
| focus-app-sessions | Your focus sessions |
| focus-app-validated-days | Your streak log |
| focus-app-stopwatch | The focus session in progress |
| focus-app-theme | Your display preference |
| focus-app-last-cleanup-day | Marker for the daily cleanup |
| focus-app-examples-seeded | Indicates whether the examples have been created |
| focus-app-analytics | Local counter that prevents sending the same event twice |
| focus-app-consent | Your answer to the audience measurement question |
This storage is strictly necessary for the application to work: without it, it cannot remember anything. As such, it does not require your prior consent.
Warning: since this data lives only in your browser, clearing its cache, using private browsing or switching devices makes it disappear for good. We have no copy and cannot restore it.
5. What the application transmits
The application measures its traffic with Umami, a cookieless analytics tool. It is the only outside service contacted, and the only place where any data leaves your device.
What is sent
Only event names, with no associated properties. The complete list is this one; there are no others:
first_open— on the very first launchreturn_day_3— if you come back after three daysreturn_day_7— after seven daysreturn_day_30— after thirty days
At most one of these events is sent per launch, and never the same one twice. On top of that comes the standard browsing data of an analytics tool: page viewed, referrer, device type, browser and country.
What is never sent
No content you enter. No task label, no habit name, no duration, no progress data. The code is written to send only fixed event names: there is no path by which the text you type could leave.
Your IP address
Like any request on the internet, these transmissions send your IP address to Umami's servers. It is used to infer an approximate country, and is then not kept as such by Umami, which moreover sets no cookie and creates no identifier that would allow you to be tracked from one site to another.
Umami acts here as a processor within the meaning of the GDPR. Legal basis: your consent.
No measurement takes place until you have answered. A question is asked when you first launch the application, with two possible answers presented on equal footing: accept or decline. Not answering counts as declining. Declining has no effect on how the application works: every feature stays the same.
You can change this choice at any time, from the shield-shaped icon at the top of the application. Withdrawing your consent is as easy as giving it. Your answer is kept for six months, then the question is asked again.
This traffic data is stored in the European Union: the storage region of the Umami account is set to Europe. No transfer outside the Union therefore takes place.
Nothing is sent when the application is used offline: the request then fails silently, with no effect on how the application works.
6. Cookies
Cerno sets no cookies, neither on the website nor in the application. The only question you are asked concerns the application's audience measurement, described in section 5. The website itself has nothing to ask you.
7. Your rights
The General Data Protection Regulation gives you a right of access, rectification, erasure, objection and restriction regarding your personal data.
In practice, you already exercise most of these rights without us: the content you enter belongs to you and lives with you. Deleting it in the application, or clearing your browser's storage, erases it truly and permanently.
As for the traffic statistics, since the data is aggregated and anonymous, we have no means of finding yours in particular. You can block it at the source by turning on your browser's tracker blocking or a dedicated extension: the application will keep working normally.
For any question, write to the address given in section 1. If our answer does not satisfy you, you can lodge a complaint with the Commission nationale de l'informatique et des libertés (CNIL), the French data protection authority.
8. Changes
Any change to this policy will be published on this page, with an updated date.