Privacy Policy

Last updated: November 3, 2026

Hearth is a free, no-signup tool. This page explains what happens to your data when you use this site — in short, very little, because there isn't much to explain.

What we don't collect

There are no accounts and no login. The calculators on this site run entirely in your browser: whatever you type into a calculator (times, weights, dates, and so on) is used to compute a result on your device and is never sent to or stored on our servers.

Cookies

One cookie, and it only remembers a language. If you read Hearth in Hebrew or Arabic — or switch back to English — we store that choice so the next page you open comes up in the same language instead of guessing again from your browser settings.

Name:lang
What it holds: a language code — en, he, or ar. Nothing else. It is not an identifier, it is not tied to an account, and it cannot be used to recognise you.
How long: one year, unless you clear it sooner.
How it's set:SameSite=Lax and Secure, so it is sent only to this site, only over an encrypted connection, and never to anyone else's.
Who doesn't get it: search-engine crawlers, which are served every language directly and are never given a cookie.

It is a preference, not tracking: no profile, no cross-site history, no advertising use, and it is never shared. Clearing your cookies removes it and the site works exactly the same afterwards — it simply falls back to your browser's language setting. Google Analytics cookies are described below.

Analytics

Cloudflare Web Analytics counts page loads on this site, and that stays as it is. It uses no cookies of its own, no cross-site tracking, and no persistent identifier that follows you between visits or between sites.

In addition, the site will keep its own daily totals of three things:

which page path was opened,
which outside host a link went to,
a few actions that a page marks for counting.

Each total is a number per path, per host, or per action, per day, and nothing else. No address, cookie, or identifier is stored with it.

So that one reader cannot inflate a count, a hash of your network address is kept for that clock hour and then deleted.

Daily totals are deleted after 90 days.

The language cookie described under Cookies is unchanged and is not part of these totals.

Google Analytics

We use Google Analytics 4 to see how many people visit and which pages help. In the European Union, the UK, Switzerland, Canada and Brazil it does not load until you accept it in the notice on the page. Elsewhere it runs unless you turn it off, and a browser that sends Global Privacy Control counts as a no.

When it runs, Google sets cookies (_ga, kept up to 13 months) holding a random identifier for your browser, and receives the page you open, the page you came from, your browser and device type, an approximate location worked out from your IP address, how far down the page you scroll and the outside links you open. It never receives your name, your email or anything you type. Google signals and ad personalisation are off, and the data is kept for 14 months. Google’s privacy policy applies (policies.google.com/privacy).

Third-party links

Some pages link out to outside sources (for example, the medical or veterinary references a calculator cites). Those sites have their own privacy practices, which this policy doesn't cover.

No sale of data

We don't sell or rent visitor data, and we share it with no one beyond Google Analytics as described above.

Changes to this policy

If what we collect ever changes — for example, if a future feature adds a contact form or email signup — this page will be updated first, with a new "last updated" date above, before that feature ships.

Contact

A dedicated contact address for this site isn't live yet. Check back here once one is — this page will link it the same day.