What we collect.And what we don't.

Battery Sensei is operated by Sandro Thabiso Schaier, self-employed individual (živnostník), with business seat at Korunní 2569/108, 101 00 Prague 10, Czech Republic. References to "we" / "us" on this page mean that operator.

Contact for any privacy-related question, request, or complaint: info@battery-sensei.app. We try to reply within a working day.

Battery Sensei the macOS app is privacy-first: it runs entirely on your Mac, with no telemetry, no analytics, no cloud account, and no outbound network calls other than the update check. The list below covers only the marketing website at battery-sensei.app and the order flow on it — which does use cookieless analytics, described in detail below.

• Language preference cookie — a first-party cookie called bs_locale, written only after you change language via the site switcher. Stores your two-letter locale (e.g. de), expires after one year, never shared.
• Purchase-confirmation flag — a session-scope sessionStorage entry called bs_purchase_tracked that prevents duplicate conversion events when you refresh the thank-you page. Cleared the moment you close the tab.
• Cookieless analytics — anonymized pageview counters and Core Web Vitals via Vercel Analytics and Vercel Speed Insights. No cookies, no cross-site identifiers; visitor IP addresses are hashed once at the edge before any storage.
• Email-signup data — only if you submit the "get the download" form: the email address you typed, the locale of the page, your IP and user-agent (for abuse triage), plus a timestamp.
• Contact-form data — only if you write to us via the contact form: name, email, message subject and body, plus IP / user-agent / referring origin for spam protection.
• Checkout data — only if you click Buy: the Polar checkout iframe collects your billing details directly. We never touch the card number; we only see what Polar reports back to us (email used, country, receipt id, fulfilment status).
• Server logs — short-lived request logs at Vercel containing path, status, user-agent and a truncated IP. Used for debugging and abuse triage. Vercel rotates these on a rolling 30-day window.

• Site functionality — language cookie, purchase-confirmation flag. Legal basis: legitimate interest (Art. 6(1)(f) GDPR) and Recital 30 of the ePrivacy Directive (strictly functional storage).
• Operating the order flow — checkout data, license key delivery, refund handling. Legal basis: performance of contract (Art. 6(1)(b) GDPR).
• Release-alert and new-app emails — only the email addresses you explicitly submit through the signup form. Legal basis: consent (Art. 6(1)(a) GDPR), withdrawable at any time via the unsubscribe link in every email, or by writing to info@battery-sensei.app.
• Cookieless analytics + server logs — a minimum signal of "the site is up and people are reading it". Legal basis: legitimate interest (Art. 6(1)(f) GDPR) in operating and improving the service. No profiling, no advertising re-targeting.
• Abuse / fraud signals — IP and user-agent on the contact and signup forms. Legal basis: legitimate interest (Art. 6(1)(f) GDPR) in protecting the service from spam, scraping and fraudulent purchase attempts.

We do not engage in any automated decision-making or profiling with legal or similarly significant effects on you (Art. 22 GDPR).

We use a small set of processors. Each has its own privacy policy, linked below. No data we hold is sold or shared with advertising networks.

• Vercel Inc. — US-based hosting provider, serves the site, runs the server functions, hashes IPs at the edge. Vercel is certified under the EU-US Data Privacy Framework. Policy: vercel.com/legal/privacy-policy.
• Polar Software, Inc. — merchant of record for all purchases. Handles payment processing, VAT, refunds, license issuance. Card data is collected directly by Polar; we never see it. Transfers to Polar (US) rely on Standard Contractual Clauses. Policy: polar.sh/legal/privacy.
• Resend, Inc. — sends release-alert and transactional emails (purchase receipt, key resend, contact-form confirmation). Email addresses you submit through our forms are mirrored to Resend audiences. Transfers to Resend (US) rely on Standard Contractual Clauses; Resend is also self-certified under the EU-US Data Privacy Framework. Policy: resend.com/legal/privacy-policy.
• Postgres database (via Vercel Marketplace) — holds the email-signup table, the contact-form table and Polar-issued license records. Provisioned in an EU region (Frankfurt) where the Marketplace provider supports it. Hosted by a Vercel-partner provider; we add their identity here once the production database is wired.

• Email-signup records — kept while you stay subscribed. We retain a hashed marker for ~30 days after you unsubscribe to avoid silently re-adding you if you re-submit the form.
• Contact-form messages — kept up to 24 months from the last reply on the thread, then purged.
• Purchase / fulfilment data — Polar, as merchant of record, retains the underlying tax invoice for the legally required period (typically 10 years under Czech Act No. 563/1991 Coll.). We retain only the licence-issuance metadata needed to re-issue or support your key, typically up to 5 years from purchase, after which it is anonymised.
• Server logs — rotated by Vercel within 30 days of the request.

Under the GDPR (and the Czech Act No. 110/2019 Coll.) you have the right to:

• Request access to the personal data we hold about you (Art. 15 GDPR).
• Ask us to correct data that is inaccurate or incomplete (Art. 16).
• Ask us to delete your data when it's no longer needed (Art. 17). For purchase data we have to retain accounting records under Czech tax law.
• Ask us to restrict processing while a correction is being assessed (Art. 18).
• Receive a portable copy of your data in a machine-readable format (Art. 20).
• Object to processing based on legitimate interest (Art. 21).
• Withdraw consent at any time — the unsubscribe link is at the bottom of every newsletter email.

To exercise any of these rights, email info@battery-sensei.app. We will reply within one month of receipt and may extend this by up to two further months for complex requests, in which case we will notify you within the first month and explain why. You also have the right to lodge a complaint with the Czech Office for Personal Data Protection (Úřad pro ochranu osobních údajů, uoou.gov.cz) or with the data protection authority in your country of residence.

When we change a material practice (a new processor, a different retention window, a new type of data collected), we update the "last updated" date at the top of this page. If a change affects your consent (for example, a new newsletter type), we will email you separately and ask before opting you in.