Privacy Policy.

Who is responsible

The controller of the personal data described here is the publisher of Sauna Metrics, identified in the legal notice. For any question or request about your data, write to support@saunametrics.app.

The app

Sauna Metrics is a sauna tracker for iPhone and Apple Watch, which also runs on iPad and Mac. There is no account and no advertising. Session contents and Health data stay on your devices. Optional usage statistics are described below.

Data stored on your device

Your sessions (times, rounds, temperature, humidity, sauna type, water, mood and stress ratings, notes, heart-rate data, photos you add), your body profile (year of birth, weight, height, biological sex, entered by you or read from Apple Health) and your settings are stored locally on your iPhone (or the iPad or Mac you use it on), using Apple's SwiftData framework and the app's own storage. Sauna Metrics does not sync this data to iCloud or to any server. On your device, the app also shares a summary with its widgets and Live Activities, indexes your sessions in Spotlight so you can search them, and schedules local reminders if you turn them on; none of this leaves your device.

Session photos

You can add a photo to a session, taken with the camera or chosen from your photo library. With the library, the app only receives the photo you pick. The photo stays with the session on your device and is not included in backup exports. It appears on the session's share card only if you share one.

Apple Health

If you choose to connect Apple Health, Sauna Metrics reads heart rate, resting heart rate, heart rate variability (HRV), VO2 max, sleep, workouts, active energy, blood pressure, body weight, height, body fat percentage, lean body mass, biological sex and date of birth. It uses them to estimate sweat loss and calories, fill in your body profile (only the year of birth is kept, for your heat age), and compare your sleep and heart data with your sauna sessions. If you keep the options on in Settings, it saves your sessions to Health as workouts, with their active energy and heart rate (recorded on Apple Watch) and the water you logged. Health data:

• Is read locally on your device only
• Is never uploaded to us or to any third party by the app
• Is never used for advertising or analytics
• Can be disconnected at any time via iOS Settings → Privacy & Security → Health → Sauna Metrics

Apple Watch

The Apple Watch app reads your heart rate and active energy during a session. The session is sent directly to your paired iPhone through Apple's Watch connection and, if you allow it, saved to Apple Health. Your iPhone sends your settings and body profile to the Watch app. Nothing passes through our servers.

App Store updates

To tell you when a new version is available, the app asks Apple's public App Store lookup service for the current version, at most every 12 hours. The request contains the app's identifier and your device's region, nothing about you or your sessions; as with any connection, Apple receives your IP address. The app also opens Apple's review prompt from time to time, managed by iOS.

Optional app usage statistics

Sharing is off by default. After your first saved session, the app asks you once whether you want to share; “No thanks” and “Share” are equally easy to choose, and closing the question counts as no. You can also turn “Share usage analytics” on or off in Settings at any time. Sharing allows the app to send up to four milestones to PostHog (United States): agreement to share, the first and second newly saved sessions after agreement, and a new save on a later day. If you agree on the question that follows your first session, that session counts as the first. Each event includes its recording time, a random identifier for this period of agreement, whether session history existed when sharing began (or that you agreed right after your first session), and technical constants identifying the app and event format. These statistics help us understand whether people begin and continue using the app. They are not used for advertising and are not joined with website visitor identities. PostHog applies a seven-year event retention window under the Pay-as-you-go plan we use. This duration is set by PostHog and cannot be shortened in the project settings. See “PostHog retention” below.

No session contents, sauna measurements, Health data, body profile, notes, photos, advertising identifier or location are included. No old history is uploaded. The random identifier links these few events, so we do not describe them as anonymous.

You may switch sharing off at any time without losing any app features. This cancels transmission in progress where possible, deletes pending events and the local analytics identifier, and stops future sends. It does not recall events already received. Turning sharing on again creates a new identifier. Events awaiting delivery stay on your device until sent or sharing is disabled. Erase all data also switches sharing off. For questions about stored statistics, contact support@saunametrics.app. The identifier is random and is not shown in the app, and we have no account or identity mapping, so we generally cannot tell which events are yours; switching sharing off stops every future send. Events already received remain subject to the PostHog retention rules described below. Legal basis: your consent (Article 6(1)(a) GDPR). See PostHog’s privacy policy.

What leaves your device only when you choose

• Backup export and import: a file with your profile, sessions (including notes and heart-rate data) and preferences, saved wherever you pick.
• Share card: an image of a session, shared through the iOS share sheet.
• AI prompt: a text with your body profile (sex, weight, height), your sessions and notes, to paste into an AI assistant of your choice. Once you share it, that service's own privacy policy applies.
• Articles: links in the app open pages of this website, described below.

We never receive any of this.

Purchases

If Sauna Metrics Pro is offered and you buy it, Apple handles the payment. The app only receives from Apple whether your purchase is active; we never see your name, email or payment details.

No tracking or advertising in the app

Apart from the optional usage statistics described above, which are off unless you agree, the Sauna Metrics app does not use:

• Analytics SDKs or crash reporting tools
• Advertising SDKs
• Tracking across other companies' apps and websites

Apple may give developers aggregated, anonymous App Store and crash statistics from users who agreed to share them with developers in their iPhone settings. Apple is responsible for that collection, under the Apple Privacy Policy.

Deleting app data

• Erase all data (Settings) deletes all your sessions with their photos, including those in Recently deleted, your body profile, your preferences, and the app's widget and Spotlight data, and switches usage statistics sharing off. It does not delete what was already saved to Apple Health.
• Delete body data (Settings) removes your weight, height, sex and year of birth.
• Unlink and delete from Health (Settings) removes the workouts, active energy and water the app saved to Apple Health.
• A session you delete, with its photo, stays in Recently deleted for 30 days, so you can restore it, then is removed for good.
• Deleting the app removes all its data from your device. Other data in Apple Health can be managed in the Health app.

The website

This website, saunametrics.app, has no account, no advertising and no cookies, and nothing you type into it (for example in the sauna finder) is sent to us. Here is everything it processes.

Hosting

The site is hosted by Netlify, Inc. (United States). Like any web server, Netlify receives the technical data your browser sends with each request (IP address, browser type, page requested, time) to deliver the page, protect the site against abuse (for example by limiting the number of requests per IP address) and keep short technical logs. These logs are kept for a limited period according to Netlify's retention rules. Legal basis: our legitimate interest in running a secure website (Article 6(1)(f) GDPR).

Audience measurement

We count page views, time on page and clicks (for example on the App Store buttons) with PostHog, provided by PostHog, Inc. (United States), to know which pages are useful and improve them. It is configured to be as light as possible:

• Nothing is stored on your device: no cookie, no localStorage, no sessionStorage. Each page view is anonymous and is not linked to your other visits.
• No session recording, no advertising, no profile, no data sold or shared for marketing.
• PostHog applies the same seven-year event retention window to website statistics, as set by the Pay-as-you-go plan we use. See “PostHog retention” below.
• Nothing is collected if your browser sends a Do Not Track or Global Privacy Control signal, or if you switch it off below.

Legal basis: our legitimate interest in measuring the audience of the site (Article 6(1)(f) GDPR). Because nothing is read from or stored on your device, no consent banner is needed; you can still object at any time.

Google Maps in city guides

City guides show venue ratings from Google Maps Platform (Google LLC, United States). We fetch these ratings through our own server, so your browser does not contact Google for them. Venue photos are different: they are hosted by Google, so loading one sends Google the technical data of your browser, including your IP address. That is why each photo only loads when you click its "Show the Google Maps photo" button. We do not send your app sessions, HealthKit data or location to Google. Google processes this data under the Google Privacy Policy. Legal basis: your consent, given by the click (Article 6(1)(a) GDPR); a click only loads that one photo, and nothing is remembered once you leave or reload the page. The source and author credits are displayed next to Google Maps content.

Settings remembered by your browser

If you pick a language in the language banner, your browser remembers it on your device (localStorage, key "sm-lang") so the banner does not come back. If you switch off audience measurement, your browser remembers that choice the same way (key "sm-analytics"). These settings never leave your device and you can delete them by clearing your browser's site data.

Links to other sites

Links to the App Store, sauna makers and venues open other sites with their own privacy policies. We earn no commission on these links.

Emails

If you write to us, we use your email address and message only to answer you, and delete them once the conversation is over, at the latest three years after your last message. Legal basis: our legitimate interest in answering you (Article 6(1)(f) GDPR).

PostHog retention

App usage statistics and website audience statistics use the same PostHog Cloud project. Its seven-year event retention window is determined by our Pay-as-you-go plan and is read-only. PostHog does not offer a shorter window on request. This window limits which events can be queried; it is not a guarantee that every event is automatically deleted at the end of seven years. PostHog states that data older than the retention period may be permanently deleted. See PostHog’s event retention documentation and retention FAQ.

Transfers outside the European Union

Netlify, PostHog and Google are based in the United States. Transfers to them rely on the European Commission's Standard Contractual Clauses included in their data processing terms and, where the company is certified, on the EU-US Data Privacy Framework.

Your rights

Under the GDPR you can ask to access, correct or delete your personal data, restrict or object to its processing, and receive it in a portable format. Write to support@saunametrics.app; we answer within one month. Because audience measurement is anonymous, the app's session data never reaches us and the optional usage statistics only carry a random identifier, we usually hold no data that we could link to you. You can also complain to your data protection authority; in France, the CNIL.

Children

Sauna Metrics is not intended for children under 15, and we do not knowingly process their data.

Changes

We will update this page if what we process changes, with a new date at the top.