Privacy
Effective 2 September 2026 · applies to the Swell Signal app and to swell-signal.com
Swell Signal predicts rideable ship wakes from public vessel traffic. It needs to know where you are watching and where to send an alert. That is the whole reason it stores anything. There are no adverts, no analytics, no trackers and no third party buying or receiving your data.
What Swell Signal never does
- No advertising, and no advertising identifier. The app never asks to track you, because it never tracks you.
- No analytics or usage-measurement product of any kind is built into the app.
- Nothing is sold, rented or shared with a data broker.
- Your location is never read in the background, and never watched continuously.
- The app asks for no email address and no phone number.
What is collected, and why
Places you save (“pins”)
A pin is a latitude, a longitude, a radius and a name you choose. It is stored so the forecast can be computed for that spot and so an alert can be sent when a wave is coming to it. If you tap Use my location, the app reads your position once to move the map marker; you can drag it anywhere before saving, and the coordinate that is saved is whatever the marker ends at. Nothing is recorded until you save a pin, and deleting the pin deletes the coordinate.
A device identifier
On first launch the app is issued a random device key. It is a random number, not derived from your hardware and not shared with anyone. It exists so your pins and alerts belong to your phone before you have created an account, and so the app can work with no account at all. It is stored on your device in the system keychain.
Notification token, if you turn alerts on
Turning alerts on registers a push token with Apple or Google and stores it against your device key, together with your time zone so quiet hours land at the right hour of your night. Push messages are delivered through Expo's push service, which passes them to Apple or Google. Turning alerts off, or deleting the app, ends this.
Basic app facts
Platform (iOS or Android) and app version, so a bug can be traced to a release. Nothing about your hardware model, and no advertising or vendor identifier.
An account, only if you make one
An account is optional. Almost everything — the map, pins, tides, wind, alerts and the widgets — works without one. Signing up stores a handle you choose and a password that is stored only as a salted scrypt hash, never as text. An account is needed for saved display layouts and for pairing a wall screen, because those follow you across devices.
Reports you choose to send
After a predicted wave you may be asked how it actually was. If you answer, the rating and any comment are stored against your account. This is what calibrates the physics, and it is the only user-written content the service holds. Answering is always optional.
Who else is involved
- Apple and Google deliver push notifications, via Expo's push service. They receive the notification and the token it is addressed to.
- OpenFreeMap serves the map background. Loading map tiles reveals your IP address and which part of the chart you are looking at to that service, as any map does.
- NOAA, WSDOT and a commercial vessel-traffic feed supply tides, ferry sailings and ship positions. Data flows from them. Nothing about you is ever sent to them.
There is no other processor, and no other recipient.
How long it is kept, and how to end it
Pins, account details and reports are kept until you delete them. Deleting a pin deletes it. Deleting your account, from Settings → Account in the app, deletes the account and everything attached to it — sessions, pins, reports and ratings — and detaches it from any device. That is immediate and cannot be undone.
Deleting the app without deleting the account leaves the account in place; delete the account first if that is what you want. To have data removed by hand, or to ask what is held, write to the address below.
Security
Everything travels over HTTPS. Session tokens and the device key are held in the iOS keychain or the Android keystore, not in ordinary storage. Passwords are stored only as scrypt hashes. No credential is ever sent to the browser or written into a page.
Children
Swell Signal is not directed at children and does not knowingly collect anything from a child under 13.
Changes
If this policy changes in a way that affects what is collected, the effective date at the top changes and the app notes it on the next update.