Privacy Policy


Your privacy is very important to us. Unlike other free online services, we have no desire to collect or sell your personal information.

Personally identifiable information is never collected, unless you explicitly provide it to us via the website contact form or the Feedback button in our apps. Feedback is sent via e-mail to our mail server, which is administered by Fastmail.

What information do we collect and how do we use it?

We do not collect personally identifiable information about you, except when you provide it to us via the the website contact form or the Feedback button in our apps. We use this information to reply to you.

We do not use or collect your precise geographic location.

Our website collects non-personally-identifiable information about your web browser and computer. We use this information to determine which web browsers and operating systems to support.

We may keep data indefinitely. We try to follow good practices for log rotation, but we also make gratuitous backups, which may inadvertently store data.

Our exercises feature a homework verification system, in which you enter a name to sign a Progress Report. This name is embedded inside the resulting verification code. When a user enters a code into the Code Checker, the original signed name is displayed. This system is explicitly designed such that names do not have to be stored on our servers. That said, in the event of an error, a verification code (and thus the name) may be included in our logs and sent to our crash report aggregator.

Do we use cookies?

Our website generates a unique identifier upon your first visit and saves it as a cookie. This identifier is anonymous, contains no personally-identifiable information, and is included in communications with our anonymous beacon system.

Our website uses HTML5 Web Storage to persist information such as: lesson view mode, exercise scores, and calculator settings.

Do we disclose any information to outside parties?

We do not sell, trade, or otherwise transfer to outside parties your personally identifiable information. This does not include trusted third parties who assist us in operating our website, conducting our business, or servicing you, so long as those parties agree to keep this information confidential. We may also release your information when we believe release is appropriate to comply with the law, enforce our site policies, or protect ours or others rights, property, or safety. However, non-personally-identifiable visitor information may be provided to other parties for marketing, advertising, or other uses.

Third party links

Occasionally, at our discretion, we may include links to third party products or services on our website. These third party sites have separate and independent privacy policies. We therefore have no responsibility or liability for the content and activities of these linked sites. Nonetheless, we seek to protect the integrity of our site and welcome any feedback about these sites.

California Online Privacy Protection Act Compliance

Because we value your privacy we have taken the necessary precautions to be in compliance with the California Online Privacy Protection Act. We therefore will not distribute your personal information to outside parties without your consent.

California Do Not Track Notice

We do not track users over time and across third party websites to provide targeted advertising and therefore do not respond to Do Not Track (DNT) signals.

Children’s Online Privacy Protection Act Compliance

We are in compliance with the requirements of COPPA (Children’s Online Privacy Protection Act), we do not collect any information from anyone under 13 years of age. Our website, products and services are all directed to people who are at least 13 years old or older.

Your Consent

By using our site, you consent to our privacy policy.

Changes to our Privacy Policy

If we decide to change our privacy policy, we will post those changes on this page.