Effective Date: October 4, 2026
Backtest Lab ("the app") lets you test how a portfolio would have performed in the past. This policy describes exactly what the app does with information. It is short because the app does very little: it does not create an account, and it does not ask for your name, email address, or phone number.
Your portfolios and results stay on your device. The portfolios you build, the conditions you enter, and the results you save are written to a database inside the app on your phone. They are not sent to us, we cannot read them, and they are deleted when you delete the app.
App settings (such as your display currency and your ad personalization choice) are stored the same way, on the device only.
Market data requests. To draw a backtest, the app asks a market data provider (Yahoo Finance) for the price history of the tickers you chose. Only the ticker symbol is sent. How much you invested, how you weighted your portfolio, and what the result was are never included in that request. As with any internet request, the provider receives the technical information needed to answer it, such as your IP address, which is handled under that provider's own policy.
Advertising. The app shows ads served by Google AdMob. Google's advertising SDK declares that it collects the following, and we list it here rather than summarising it, because a summary is where the inconvenient item goes missing:
Where the law requires a choice (for example in Europe), you can change whether ads are personalized in the app's settings, and on iOS your App Tracking Transparency choice applies as well. Google describes its own processing at policies.google.com/technologies/partner-sites.
Your choices in the EEA, the UK and Switzerland. If you use the app in the European Economic Area, the United Kingdom or Switzerland, the app asks for your consent to ads through Google's User Messaging Platform (UMP) before personalised ads are shown. Where the law asks for your choice, the app shows an "Ad personalisation" row in Settings. You can open it at any time to change or withdraw your consent; the choice is stored on your device and applies to the next ads you see. The app itself does not send your personal information to a server; the only data collected for advertising is collected by Google's advertising SDK, as listed above. Personalised ads are shown only with your consent (GDPR Art. 6(1)(a)); non-personalised ads may still be shown without it. You can withdraw consent at any time as described above. Because the app keeps no copy of your data on a server, requests to access, correct or erase it are answered by deleting the app. For Google's processing, see Google's policy linked above. For questions about this policy, see "Contact" below.
Sharing a result. When you share a result, what is transmitted is the content of the image the app creates at that moment. You choose when this happens; nothing is shared automatically.
The app contains no analytics or usage-tracking code of our own. We do not record which screens you open or which features you use. We do not sell personal information, and we do not share it with third parties for their own advertising purposes. Apart from the advertising identifier used by AdMob as described above, the app does not collect device identifiers.
The app is not directed to children under 13, and we do not knowingly collect personal information from children under 13.
Because everything is stored on your device, deleting the app deletes your data. There is no server-side copy for us to look up, correct, or erase on request. To reset ad personalization, use your device's advertising settings and, where the law requires a choice, the app's own setting.
If what the app does changes, this page and the policy shown inside the app (Settings → Privacy Policy) are updated together, and the effective date above is revised. The two are meant to state the same facts.
Questions about this policy can be sent to developer.younghwi@gmail.com.
Backtest Lab is a calculator that shows what past data would have produced. It is not investment advice, and past results do not indicate future returns.