Derny — Privacy Policy
Last updated: August 19, 2026
Derny (“the app”, “we”) is an indoor cycling training app that connects to a Bluetooth
smart trainer and heart-rate monitor and drives adaptive workouts based on your live metrics.
This policy explains what data the app handles and why.
The short version: The app works fully without an account, and
in that mode your data stays on your device. If you choose to sign in, your account email and your
workouts and ride history are stored in our cloud so they sync across your devices. The app has no
ads or advertising trackers. The website counts visits without cookies, and uses limited conversion
measurement for our Reddit ads.
Information we handle
- Account information. If you choose to create an account or sign in (with Apple,
Google, or email), we store your email address to identify your account. Signing in is optional.
- Workouts and ride data. The workouts you create and the rides you record,
including metrics such as power, cadence, heart rate, duration, and timestamps. This is stored on
your device, and synced to our cloud only when you are signed in.
- Bluetooth device data. The app reads live data from your smart trainer and
heart-rate monitor over Bluetooth to display metrics and adjust workout targets. Your ride
metrics are processed on your device and leave it only as part of a ride you save while signed
in. (Separately, we send limited technical information about the trainer itself; see below.)
- Trainer diagnostic & compatibility data. When you are signed in and connect
a smart trainer, we record limited technical information about that trainer: its advertised model,
the control features it reports (such as ERG/power-target and resistance support) and their
supported ranges, and whether the app was able to control it. We use this only to keep the app
working reliably across the wide range of trainers our users own. It contains no health or ride
data.
- Apple Health (optional, write-only). With your permission, the app saves your
finished rides to Apple Health as indoor cycling workouts. The app does not read any data
from Apple Health. Health data is managed by Apple on your device.
- Beta signup email. If you ask for a beta invite on our website, we store the
email address you enter so we can send you your TestFlight invite and occasional beta updates, and
so you can reply to us. We record whether you opened or clicked that email to gauge interest. You
can unsubscribe at any time via the link in the email, and we will delete your address on request.
We do not sell it or use it for advertising. We also store how you reached the form: any campaign
tags in the link you followed, and the address of the page that linked to us, without its query
string. That tells us which of our own posts and ads actually bring riders in. To carry it across
our own pages, your browser holds it in session storage, which belongs to one tab and is gone when
you close it. We receive none of it unless you submit the form.
- Reddit ad measurement. The beta signup page uses the Reddit Pixel. It records a
page visit and, only after our signup endpoint accepts the form, a signup event. We do not give
Reddit your email address, platform choice, form contents, account data, or ride data. Reddit
receives the browser request and its own identifiers so it can attribute those two events to our
ads. The pixel is not part of the app.
- Website visit counting. Our website pages use Cloudflare Web Analytics so we
can see how many people reach them. It records the address of the page you opened, the address
of the page that linked you to it, basic timings for how quickly the page loaded, and, from the
request your browser makes, your country, your browser, your operating system, and whether you
are on a phone, tablet, or desktop. It sets no cookies, reads nothing from your browser storage,
and does not fingerprint your device, so it cannot recognize you from one visit to the next or
follow you to other sites. It is not part of the app.
The app does not collect your location, contacts, photos, or advertising
identifiers, and uses no third-party advertising or analytics/tracking SDKs.
How we use it
Data is used solely to provide and improve the app’s features: to store and sync your workouts and
ride history, show your training metrics, (optionally) mirror finished rides to Apple Health, and keep
the app working reliably across different smart trainers. We use the website events described above
only to measure our own Reddit ads, and the visit counts only to see how many people reach our pages
and how many of them go on to sign up. We do not use your email, account data, or ride data for
advertising.
Where your data is stored
When you are signed in, your account and ride data are stored using
Supabase, our cloud backend provider, which
processes this data on our behalf. When you are signed out, your data stays only on your device. Our
website is served by Cloudflare,
which also provides the cookieless visit counting described above and processes it on our behalf.
Sharing
We do not sell your personal data. We share account and ride data only with the service providers
above, strictly to operate the app, and where required by law. We share the limited website events
described above with Reddit to measure our ads, but not your email address or app data.
Your choices and data deletion
You can use the app without an account. If you have an account, you can request deletion of your
account and associated cloud data by emailing us at the address below; we will delete it within a
reasonable period. Workouts saved to Apple Health are controlled by you in the Apple Health app.
Security
Data in transit is protected with standard encryption (HTTPS/TLS), and cloud data is protected by
access controls so each account can only reach its own records.
Children
Derny is not directed to children under 13, and we do not knowingly collect personal information
from them.
Changes
We may update this policy as the app evolves. Material changes will be reflected here with a new
“last updated” date.
Contact
Questions or requests: leo@derny.app.