Privacy

• We collect what we need to run Checksum: your email address, your study activity and anything you send us.
• No ads, no tracking pixels and no third-party analytics. We count page views and sign-ups ourselves, without IP addresses.
• We never sell your data or share it for advertising.
• Tips go through Stripe’s own payment page. No payment details reach Checksum.
• Your study data is never sent to an AI provider.
• You can have a copy of your data, or have your account deleted, at any time.

Corratech LLC, [Mailing address], runs Checksum and is responsible for your data. Write to us at [email protected].

• Your account. Your email address, and a name only if you choose to give one.
• Your study activity. Your answers, the lessons you read, your review schedule, practice exams and readiness. In the coding track your code runs in your own browser; we store only how many tests passed and how long they took, never the code.
• What you send us. The text of a “Something off?” report, and any email you write to us.
• Sign-in and security records. Sign-in codes and links, stored only as scrambled digests (hashes) that expire after 10 minutes. For each signed-in session, your browser’s user agent (its name and version) and a keyed hash of your IP address, never the address itself. Rate-limit counters keyed the same way.
• Usage counts. Events such as a page view, a started diagnostic or a tap on the support link, stored in our own database. They may be linked to your account, or to a random ID if you are not signed in, but never to an IP address.
• Before you sign in. If you take a diagnostic without an account, your answers are stored with no name or email, and a signed cookie in your browser remembers which ones are yours. When you sign in, they move to your account.

• Payment details. If you tip, you pay on Stripe’s page, under Stripe’s privacy policy. Stripe tells us the amount and the details you enter there, as it does for any business it pays, and we do not link tips to your Checksum account.
• Advertising or tracking data. We add no advertising, analytics or tracking scripts, and no pixels.
• Your study data for AI. Our lessons and questions are written and checked before they are published, and studying never sends your data to an AI model. If we ever add a feature that would send your text to an AI provider, we will say so here first and label the feature.

We use only what the site needs to work, plus your display choices:

• __Host-rsid keeps you signed in. It lasts 30 days and renews while you use Checksum.
• __Host-rcsrf protects forms against requests from other sites. It lasts until you close the browser.
• __Host-ranon remembers a diagnostic you take before signing in, for up to 30 days.
• Browser storage on your device keeps your theme and text size, and when you last closed the tip note. It never leaves your device.

There are no advertising or analytics cookies.

• To run Checksum and save your progress across devices.
• To send sign-in codes, one welcome email, updates on reports you file, and only the reminder emails you turn on.
• To read and fix the reports you send.
• To keep the service secure and stop abuse.
• To count how Checksum is used, in total, so we can improve it.

We do not use your data for advertising, and we never sell it.

A few services do work for us, and only for us:

• Resend sends our email, so it receives your email address and the message.
• Cloudflare delivers the site and protects it from attacks. All traffic to Checksum passes through its network.
• Microsoft Azure stores our encrypted database backups.

We share data with anyone else only if the law requires it.

• Signed-in sessions end after 30 days without use.
• Sign-in codes and links expire after 10 minutes.
• Email delivery records are kept for 180 days.
• Your account and study activity are kept until you delete your account. Then we remove your personal data and keep only anonymous totals.
• Encrypted backups roll off on a schedule: hourly copies for 2 days, daily copies for 30 days and monthly copies for 12 months. Deleted data leaves the backups as they expire.

You can ask for a copy of your data (as a JSON file), ask us to correct it, or delete your account. Export and delete buttons are coming to Account; until they arrive, email [email protected] from the address on your account and we will do it for you.

Reminder emails are off unless you turn them on, and each one has a link to turn it off again. Depending on where you live, local law may give you other rights too; write to us and we will help.

Checksum is not meant for children under [Minimum age], and we do not knowingly collect their data. If you think a child has given us data, write to us and we will delete it.

Checksum’s server and backups are located in [Data location]. If you use Checksum from somewhere else, your data is transferred there.

The current version always lives here, with its date. We will give notice on the site before a significant change takes effect.

Email [email protected], or write to Corratech LLC, [Mailing address].