Privacy Policy

Last updated: October 25, 2026

Athylos ("Athylos," "we," "us") provides AI-powered swim training for iPhone and Apple Watch. This policy explains what information we collect through the Athylos app, the Athylos Watch app, and this website, how we use it, who receives it, and the controls you have. The short version: your data powers your own training, anything beyond that is opt-in, and we never sell your data or use it for advertising or tracking.

1. Information we collect

Account information

When you sign in with Apple, we receive your Apple user identifier and — on first sign-in only, if you choose to share them — your name and email address. Those are stored on your Athylos account. Server records use that account identifier. The data is pseudonymous, not anonymous: it can still be linked to your account so we can provide the service and honor deletion.

Training profile

Age, gender, weight, training shape, goal event, best and goal times, and equipment are sent with a workout request and stored with a saved workout. Age and gender are included in the coaching prompt. Body weight is stored with the request and is not written into that prompt. The name on your training profile is sent with the request if the app includes it. Height, resting heart rate, and VO2 max are read for the on-device analytics screen and are not uploaded. Style notes, your training week, and your training brief are stored on your account so they survive a reinstall.

Health and workout data

With your permission, Athylos reads Apple Health and records workouts from the Athylos Watch app: source, timestamps, pool length, distance, duration, splits, strokes, heart-rate summaries, energy, and supported lifting or cross-training facts, plus set and per-rep structure. Saved workouts are stored on your account whether or not analytics sharing is on. Apple Health facts are uploaded only if you opt in, as described below. Health and workout data is never used for advertising and is never sold.

AI coaching, and asking first

Workout generation, revisions, chat, and reading a photographed workout use Google Gemini via Vertex AI, run on Google Cloud. The app sends nothing to it until you agree, either during onboarding or in Settings → Data Sharing → AI Coaching, and you can turn it off there at any time. A request carries your prompt or chat message and the training-profile facts described above, including age and gender, or the photo you chose. It is not labeled with your email or your Apple ID. Google does not use these requests to train its models. With AI coaching off, recording swims, your analytics, and workouts you have saved keep working; generation, chat, and photo import stay off.

Photographs of a workout

If you photograph a whiteboard or a printed workout, the photo is uploaded to our servers and sent to Google Gemini so it can be read into a session. We do not store the image on your account. A transcript of the words on the board, keyed only by a hash of the image and not by your account, may be cached for 30 days so the same photo is not read twice. The workout you then save is stored on your account like any other workout.

Chat, prompts, and saved workout text

Chat messages are sent to the model so it can answer. Chat bodies are not stored on your account. A prompt you save with a workout is stored with that workout. An async generation or chat job can hold a message for about an hour, then it is deleted. We do not copy prompts, chat, or assistant responses into analytics or diagnostic telemetry. Chat telemetry, when analytics is on, is metadata only: turn identifier, action, length, latency, token counts, outcome, and a server-keyed fingerprint.

Support tickets

A ticket you send from Settings → Contact Support includes the subject, your message, your signed-in email so we can reply, and the app version. It is correspondence, not analytics, and it is sent whether or not analytics sharing is on.

Purchases

Subscriptions are billed by Apple through the App Store. After a purchase or restore, the app sends us the signed transaction. We store the product, the original transaction identifier, the expiry, whether it is a trial, and the plan that transaction unlocks. We never receive your card number or other payment details. Apple keeps those.

Essential service records

Even when analytics sharing is off, Athylos stores limited content-free records needed to operate and troubleshoot workout generation, chat, saving, Watch delivery, and telemetry delivery. These records may include operation, outcome, timing, provider and model, token counts, retry count, correlation ID, and a coarse error category. They do not include prompts, assistant responses, names, emails, access tokens, or free-text settings.

Opt-in analytics

During onboarding you choose whether to share pseudonymous app usage, sanitized settings, Apple Health workout facts, workout execution, and aggregate Watch sensor facts. You can change this at any time under Settings → Data Sharing → Share Analytics. Settings analytics uses coarse categories and booleans and excludes names, exact age, gender, exact goal times, custom-equipment text, and prompts. Aggregate sensor facts are the one-second motion summaries described under Motion. Depth is not recorded.

Motion

Apple Watch motion is processed on the watch during a swim to detect turns and advance guided sets. This build does not upload high-frequency raw accelerometer or gyroscope files. If a raw chunk reaches the phone, the phone deletes it instead of storing it. The watch keeps the newest 7,200 one-second summaries (about two hours) and drops older ones. Each summary is a timestamp, accelerometer variance, and gyroscope magnitude. Depth is not recorded, so it is not uploaded and it is not a location. Sending the summary to the phone keeps it under 55 KB: the newest summaries that fit are kept, and the list is omitted if even one summary cannot fit. If the packet is still too large, these are omitted first: cumulative snapshots, distance snapshots, stroke snapshots, session events, user actions, raw lap events, and clean splits. Identity and timing stay. When Share Analytics is on, the phone can upload the summaries that arrived and the scalar motion facts on the session (mean and peak acceleration, mean and peak rotation, sample rate, and turn count). Any raw research objects left from earlier test builds are deleted after 60 days.

Crash and performance data

The iPhone and Watch apps send scrubbed crash reports, a sample of performance traces, and targeted nonfatal diagnostic reports to Sentry so we can fix crashes. The iPhone samples about one performance trace in five, and the Watch about one in ten. The server sends scrubbed error reports and does not send performance traces. Before a report is sent, the account is removed. Names, emails, prompts, model responses, access tokens, and request bodies are stripped. Reports are tagged by app release and environment.

Sharing a swim

When you share a swim, Athylos draws the image on your phone and hands it to the app you pick: Instagram, Messages, Photos or another app in the share sheet. Athylos does not send the image, or anything else, to Meta or to that app's servers; what happens after you post it is governed by that app's own policy. For Instagram Stories, Athylos includes its Facebook App ID, which tells Instagram the share came from Athylos and identifies nothing about you. Heart rate appears on a shared image only if you turn it on.

Strava

Strava. Connecting Strava is optional. Nothing is sent to Strava until Athylos turns the integration on. When it is on and you connect, Athylos stores the access and refresh tokens Strava issues and can post a swim you choose, or every finished Apple Watch swim if you turn auto-post on: the activity name, start time, duration, distance, a short description, and lap times when the swim has them. We do not send your Apple ID, email, heart rate, or location to Strava. Disconnect, and Delete Account, revoke that access at Strava and delete the tokens we stored. Strava's privacy policy then applies to the activity on Strava.

What we do not collect

Website and beta list

If you join our beta waitlist on this website, we collect the email address you submit and use it only to contact you about Athylos beta access and launch updates. You can unsubscribe at any time using the link in any email or by contacting us.

This website does not run web analytics. Cloudflare Web Analytics is off. The site does not count page views and does not set an analytics cookie.

2. How we use information

We do not sell your personal information, do not use it for third-party advertising, and do not track you across other companies' apps or websites.

3. Service providers

We use a small number of providers to operate Athylos. Each processes data only to provide the service described here:

Strava — only if you connect it, and only after Athylos turns the integration on. We send the swim described above and store the tokens Strava issues until you disconnect or delete your account. Strava's privacy policy then applies to the activity on Strava.

4. Data retention

5. Account deletion

You can delete your account at any time in Settings → Delete Account. Deletion removes your identity record, saved workouts, sessions, async-job copies, telemetry documents, user-linked analytics events, sensor-upload records, sensor objects, support tickets, Strava tokens, and the purchase records we hold (the App Store subscription itself stays with Apple until you cancel it there). Chat bodies are not stored on the account. The hash-only photo transcript cache is not tied to an account and expires on its own schedule. Only genuinely unlinked cohort aggregates may remain. Deleting the account invalidates every session immediately, on every device. We keep a revocation marker — the Sign in with Apple subject and the time those sessions were cut off — so a session from before the deletion cannot be used again, including if you sign in later and start fresh. The marker stores no name, email, workouts, or other profile data. You may sign in again afterward and start fresh. You can also request deletion at the address below.

6. Your rights

Depending on where you live, you may have rights to access, correct, delete, or export your personal information, and to object to or restrict certain processing. You can exercise most of these directly in the app (profile editing, the Data Sharing controls including AI Coaching, account deletion). For anything else, contact us and we will respond within the timeframe required by applicable law. We do not discriminate against you for exercising your privacy rights.

7. Security

Data in transit is encrypted with TLS. Server-side data is stored on Google Cloud with access restricted to service accounts that need it. Authentication uses Sign in with Apple. A session token lasts up to 30 days and can be renewed from the app while the account exists; deleting the account invalidates it immediately. No method of transmission or storage is 100% secure, but we work to protect your information using industry-standard practices.

8. Children

Athylos is not intended for, and may not be used by, anyone under 13 years of age. We do not knowingly collect personal information from children under 13. If you believe a child has provided us personal information, contact us and we will delete it.

9. Changes to this policy

If we make material changes, we will update the date at the top of this page and notify you in the app or by email before the changes take effect. Continued use of Athylos after changes take effect means you accept the updated policy.

10. Contact

Questions or requests? Email us at support@athylos.com or use Settings → Contact Support in the app.