NetGuard is a firewall application that allows users to block access to the internet without requiring root access. It provides both simple and advanced methods to control which applications and addresses can connect to Wi-Fi and mobile networks. By blocking internet access, users can reduce data usage, save battery life, and enhance privacy. The app is easy to use, open source, and does not include any tracking, analytics, or advertisements. It is actively developed and supported, compatible with Android 5.1 and later versions, and supports both IPv4 and IPv6 protocols.

In addition to the basic features, NetGuard also offers PRO features for advanced users. These include the ability to log outgoing traffic, search and filter access attempts, and export PCAP files for traffic analysis. Users can also allow or block individual addresses per application, receive notifications for new applications, and display network speed graphs in the status bar. The app provides a material design theme with light and dark options, and users can choose from five additional themes.

NetGuard uses the Android VPNService to route traffic to itself, allowing it to filter traffic on the device rather than on a server. However, this means that only one app can use this service at a time due to Android limitations. The source code for NetGuard is available for those interested in reviewing it. Users can contact the developer via email for any questions or problems, and there are opportunities to help translate the app into different languages or participate in the test program.