Privacy Policy — FocalMath

The Short Version

The calculators on FocalMath run entirely in your browser. The numbers you type in — sensor format, focal length, aperture, distance, ISO, whatever a given tool asks for — are never sent to a server, never logged, and never stored anywhere by us. When a calculator encodes your inputs into the page's URL, that's so you can bookmark or share a specific result; it isn't collected or read by us.

Analytics

We use Google Analytics 4 to understand which pages and calculators get used, in aggregate, so we know what to build or fix next. GA4 uses cookies and collects standard web-analytics data — pages visited, approximate location at the country/region level, device and browser type, and how you arrived at the site. It does not know what values you typed into a calculator, because those never leave your browser. Google's own privacy policy governs how it processes this data on our behalf; you can opt out of Google Analytics tracking network-wide using Google's official browser add-on, and many browsers and ad blockers block it by default.

We also use Vercel's built-in web analytics, which is designed to be cookieless and does not track individuals across sites — it reports aggregate traffic and performance metrics for this site only.

Advertising

We plan to run display advertising through Google AdSense to help cover hosting and development costs. AdSense and its partner networks may use cookies and similar technologies to personalize the ads you see based on your browsing activity across sites, not just this one. You can review and adjust your ad personalization settings through Google's My Ad Center, and general opt-out information for participating networks is available at aboutads.info. We do not run our own cross-site advertising tracking network beyond what these third-party services provide.

Security

We take reasonable technical measures to protect any information we do collect, but no method of transmission or storage is 100% secure, and we can't guarantee absolute security. If you become aware of a security issue affecting this site, please report it via the contact page.

Newsletter and Contact

If you sign up for updates or send us a message through the contact page, we store the email address and message content only for the purpose of responding to you or sending the updates you asked for. We do not sell or rent this information to third parties. Every newsletter email includes an unsubscribe link that removes you immediately.

Payments

Purchases and donations are processed by Stripe. We never see or store your full card details — Stripe handles that directly under its own security and privacy practices, which you can review on Stripe's own site. We receive only what's needed to fulfil an order or confirm a donation: your email address, the amount, and a transaction reference.

Cookies in General

Beyond the analytics and advertising cookies described above, this site does not set its own custom tracking cookies. Any preference you set in a calculator (like a default sensor format) that persists between visits is stored locally in your browser's storage, not on our servers, and is never transmitted to us.

Your Rights

Depending on where you live, you may have rights to access, correct, or delete personal data we hold about you — practically, this is limited to your email address if you've contacted us or subscribed to updates. Contact us to exercise any of these rights and we'll respond as quickly as we reasonably can.

Data Retention

We keep contact-form messages and newsletter subscriptions only as long as reasonably needed to respond to you or continue sending the updates you signed up for. You can unsubscribe from the newsletter at any time using the link in every email.

Children's Privacy

This site is not directed at children under 13 and we do not knowingly collect personal information from them.

Changes to This Policy

If this policy changes materially, we'll update this page and adjust the date at the top. Continued use of the site after a change means you accept the updated policy.

Contact

Questions about this policy can go to the same address listed on the contact page, and we're happy to clarify any part of it in plain language if the legal phrasing above is unclear.