PACO is a mobile, behavioral research platform created by Paco Developers. It is a free app available on Android devices. The app is designed to help users build quantified self or behavioral science experiments. Version 4 of the app comes with a completely redesigned API and new features.

It is important to note that PACO asks for several permissions upon installation. However, by default, the app only uses the internet permission to confirm your Google account and communicate with the Paco server to retrieve experiments and send responses. Each experiment you join will show you what data it collects and ask for your consent before you join. To learn more about how Paco experiments use services that require permissions, visit their website FAQ. Additionally, some experiments for user research triggers require Accessibility services, which you can turn on or off at any time.