Privacy Policy

Last updated: 5 August 2026

The short version

ChartGrade has no accounts and no sign-in. We do not ask for your name, email address, or phone number, and we have no way to identify you. Your saved chart readings are stored on your device, and we cannot read your history.

What happens when you read a chart

When you analyse a chart, the image is sent to our server, which passes it to Google’s Gemini API to be read. The resulting analysis is returned to your device and saved there.

We keep a copy of the analysis result, keyed to a one-way fingerprint (hash) of the image, for up to 30 days. This is what lets the same chart always produce the same reading rather than a different answer each time. The fingerprint cannot be turned back into the image. We do not store the chart images themselves.

Images sent to Google are processed to produce your analysis. Google’s handling of that data is governed by their own terms and privacy policy.

Subscriptions

Subscriptions are handled by the store you bought through — Apple’s App Store or Google Play — and by RevenueCat, our subscription provider. To check whether your subscription is active, the app sends an anonymous identifier generated on your device. It is not linked to your name, your email, or your store account, and we never receive your payment details.

We use that same anonymous identifier to limit how many analyses can be requested in a given period, to prevent abuse of the service.

What we do not do

• We do not collect personal information.
• We do not use advertising or tracking SDKs inside the app.
• We do not sell or share data with data brokers.
• We do not build a profile of you across apps or websites.

Your data, and deleting it

Because there is no account, there is nothing for us to delete on request. Deleting the app removes every reading stored on your device. Cached analysis results on our server expire automatically within 30 days.

Note that this also means your readings are not backed up by us. On Android, your device may include app data in Google’s automatic backup to your own Google Drive; that copy belongs to you and is governed by your device settings, not by us. Your subscription is unaffected and can be restored through the store you bought it from.

Children

ChartGrade is intended for adults and is not directed at children.

Changes

If this policy changes, the date at the top changes with it.

Contact

Questions about this policy: privacy@twiddlethumbstudio.com