Privacy policy

Effective date: July 26, 2026

The short version

• Your workout, health, and profile data is stored in your own private iCloud account (via Apple CloudKit), not on servers we operate or control.
• The app contains no analytics, advertising, or crash-reporting SDKs. We do not track you across apps or websites, and we do not sell or share your data with third parties for advertising. The MCP server that connects your AI (also known as an AI Connector) keeps brief technical logs so it can be fixed when it breaks, described below, and they contain none of your training or health content.
• HealthKit data is used to power features inside the app and never leaves your device. Separately, your workout logs include summary health metrics (average and max heart rate, calories, distance). If you connect an AI client, it can read those logs, along with your profile, goals, plans, and equipment.
• There is no Parameter account and no in-app sign-in. Connecting an AI client is authorized on Apple’s own iCloud sign-in page, and we never see your Apple ID password. Access is per client and revocable at any time in Settings.
• You can permanently delete your data from within the app at any time.

Information Parameter collects

Health and fitness data (Apple HealthKit)

With your permission, Parameter reads the following from Apple Health:

• Workouts
• Heart rate
• Active energy burned
• Distance (walking/running, cycling, swimming, and rowing where applicable)

Parameter writes the following to Apple Health:

• Workouts you complete in the app, including type, duration, and interval segments

This data is used only to power in-app features: for example, showing live heart rate during a session, calculating training metrics, and saving your completed workouts to Health. It is read from and written to Health directly on your device. Parameter does not transmit this HealthKit data to us, to any analytics service, or to any third party.

Separately, when you complete a workout, Parameter computes summary health metrics for it (average and max heart rate, calories, distance) and stores them as part of your workout log. That log is synced to your own private iCloud database like the rest of your Parameter data. See “Workout plans and logs” and “Connecting an AI client” below for what that means if you connect an AI.

Motion and fitness activity

Parameter uses motion data (Core Motion) on-device to detect when a walk, run, hike, or ride has stopped, so it can offer to pause your workout automatically. This data is not stored or transmitted off your device.

Location

Parameter uses your location, when granted, to show live distance and pace during outdoor workouts. Your location is used in real time on-device and is never stored or shared.

Profile and training information

Information you enter directly, such as:

• Display name
• Training goals and constraints
• Preferred units
• Weekly availability
• Notes used to personalize your training plan
• Heart rate zones
• Time zone
• Equipment you have access to

Your age, if you provide it, is used only on-device (e.g., to suggest default heart rate zones) and is never synced or transmitted anywhere.

Workout plans and logs

Your training plans, workouts, exercises, sets, and logged results are stored so the app can track your training history and progress over time. Logged results include the summary health metrics described above (average and max heart rate, calories, and distance for a given workout), along with any notes and effort ratings you enter. If you connect an AI client, it can read this history, including those summary metrics, notes, and effort ratings.

Subscription status

Parameter offers an optional paid feature (“AI connection”) via a monthly auto-renewing subscription with a free trial. Payment is processed entirely by Apple through StoreKit, and Parameter never receives or stores your payment card details. We store only whether your subscription is currently active, so the app can unlock the corresponding features.

Connecting an AI client (optional)

Parameter has no app account and no in-app sign-in. If you choose to connect a third-party AI client (for example Claude, or another MCP-compatible client) to your training data, that connection is authorized on Apple’s own iCloud web sign-in page at the time you connect, not inside Parameter. We do not see or store your Apple ID password as part of this process.

Once connected, an AI client can:

• read your profile, goals, equipment, and heart-rate zones
• read your workout history and logs, including notes, effort ratings, and workout health metrics (average and max heart rate, calories, distance)
• create and update plans and workouts

You can review and revoke access for each connected client at any time in Settings. Revoking blocks that client’s access within a minute.

How your data is stored and synced

Parameter stores your data in a private CloudKit database tied to your own iCloud account. This is the same private-database mechanism Apple provides to any app you use. Apple, not Parameter, controls access to and encryption of this store, and your data is never placed in a public or shared CloudKit database. Apple also determines where this data is physically stored, and may process it in countries other than your own as part of ordinary iCloud operation.

If you connect an AI client, an MCP server we operate (built on Cloudflare Workers) reads from and writes to your own private CloudKit database on behalf of that client, scoped to what you authorized. The MCP server does not keep a separate copy of your health or workout data; it acts strictly as a proxy to your own private store. The only piece of your data the MCP server stores is an encrypted iCloud authorization token for your account, which it needs to act on your behalf. One token covers all the clients you connect. If you revoke every connected client, or delete all your Parameter data, the MCP server deletes the token within a few hours. It is also deleted whenever the MCP server’s authorization with iCloud ends or is invalidated. Because Cloudflare Workers run on a global network, that encrypted token may be processed in countries other than your own.

The MCP server also keeps short-lived operational records, so that it can be repaired when it breaks. For each request your AI makes, it writes one log line recording which tool was called, when, how long it took, whether it succeeded or which error it returned, and a one-way hash of your account identifier that cannot be turned back into your identity. Those log lines never contain your workout content, notes, effort ratings, health values, profile text, or any authorization token, and they are deleted automatically after a few days. Separately, the MCP server keeps running totals for service health, for example how many plan updates succeeded or failed across everyone using it. Those totals carry no account identifier at all and are kept for a few months.

Security

The data we hold ourselves is limited to the encrypted connection token and the operational records described above, and we protect them with standard encryption and access controls. Everything else, your workout, health, and profile data, is protected by Apple’s iCloud security, which we do not control and cannot bypass. Because Parameter has no accounts, using the app gives us no email address or identity for you, so we cannot contact individual users. The one exception is the optional website mailing list described below, which nobody joins without asking to. If we become aware that tokens we hold have been accessed without authorization, we will immediately revoke the affected connections, which cuts off that access and requires a fresh Apple sign-in to reconnect, and we will post a notice at parameterfit.com.

Data we do not collect

Parameter does not include any analytics, advertising, or crash-reporting software development kits (SDKs). We do not track your activity across other companies’ apps or websites, and we do not use your data for advertising or sell or share it with data brokers or any other third party.

The website

This policy is about the app. The website at parameterfit.com is separate. Using Parameter never puts your email address in our hands. The only addresses we hold are ones people typed into a sign-up form themselves.

The mailing list. The website footer carries an optional sign-up form for Parameter news. If you enter your address, we send one confirmation email, and you are added to the list only if you click the link inside it. If you do not click, nothing further is sent and the address is not used. The list is operated on our behalf by MailerLite, which does not use it for any other purpose. Messages come from [email protected] and every one carries an unsubscribe link. You can also ask to be removed at any time at [email protected]. We do not add app users to this list, we do not buy or import addresses, and we do not sell or share it.

Website analytics. The website uses Cloudflare Web Analytics to count page views, so we can tell which pages people find useful. It records the page visited, the referring page, page load timings, and coarse details such as country, browser, and device type. It sets no cookies and uses no browser storage. We do not receive names, email addresses, or any way to identify you from it, and we do not combine it with anything else. Cloudflare also states that it does not track individual end users across the sites that use it. It is not present in the app, which still contains no analytics software of any kind.

Press. [email protected] reaches us for media requests. It is an ordinary mailbox and holds only what you send to it.

Children’s privacy

Parameter is not directed at children, and we do not knowingly collect personal information from anyone under 13. If we learn that we have collected personal information from a child under 13, we will delete it.

Your choices and control over your data

• Access: All of your profile, plan, workout, and log data is visible to you within the app at any time.
• Permissions: You control HealthKit, motion, and location access through iOS Settings and can revoke any of them at any time. Revoking a permission may limit related features.
• Deletion: You can permanently delete your Parameter data from Settings → “Delete all my data.” This removes your entire private CloudKit data store (profile, equipment, plans, workouts, logs, connected clients, and subscription record) as well as the corresponding local data on your device. Because Apple does not allow third-party apps to delete data from Apple Health on your behalf, any workouts already saved to Health are not affected by this action and must be removed directly in the Health app if desired.
• Revoking AI client access: You can revoke any connected AI client from Settings at any time; the MCP server then refuses that client’s requests. Revoking your last connected client also deletes the stored connection token within a few hours.
• Data protection law: If law in your location (for example the GDPR, UK GDPR, or a US state privacy law) gives you rights to access, correct, delete, or export personal data, the controls above cover nearly all of it, since almost everything lives in your own iCloud account rather than ours. We do not sell or share personal information, so there is nothing to opt out of. For anything not covered above, contact us at the address below.

Law enforcement and legal requests

We may disclose the limited information described in this policy if required to do so by valid legal process, such as a court order or subpoena.

Changes to this policy

If we make material changes to this policy, we will update the effective date above and, where appropriate, notify you within the app.

Contact us

If you have questions about this policy or your data, contact us at [email protected].