NetGuard: Open-Source Firewall for Android

NetGuard is an internet security application for Android that allows users to restrict internet access on a per-application and per-address basis. Developed by FairCode B.V., the tool provides a mechanism to manage network connectivity without requiring root permissions on the device.

The software is designed to help users reduce mobile data usage, conserve battery life and increase device privacy by preventing specific applications from accessing the internet in the background or on mobile data.

Technical Implementation and Architecture

NetGuard operates by utilizing the Android VPNService to route network traffic to itself. This architecture enables the application to perform filtering locally on the device rather than routing traffic through an external server.

Because of the way Android manages these services, only one application can utilize the VPNService at a time. This creates a technical limitation where NetGuard cannot operate simultaneously with other VPN applications.

The application supports Android 5.1 and later versions. It provides compatibility for both IPv4 and IPv6, as well as TCP and UDP protocols. The software supports tethering and multiple device users.

Core Features and User Control

Users can individually allow or deny applications access to Wi-Fi and mobile connections. The software includes several optional configuration settings to refine this control, including:

• The ability to block system applications.
• Options to block internet access specifically when roaming.
• The ability to allow internet access only when the screen is on.
• Notifications that alert the user when an application accesses the internet.
• The capability to record network usage per application and per address.

The application is developed as a 100% open-source project. It is built without advertisements, tracking, or analytics, and does not feature calling home functionality.

Advanced and Pro Functionality

While basic blocking is available to all users, NetGuard offers a set of pro features available via in-app purchase. These tools provide deeper network monitoring and granular control over outgoing traffic.

One primary pro feature is the traffic log, which allows users to display and export a detailed outgoing IP traffic log for all applications. This allows for the analysis of exactly what a device is doing at any given moment, including the export of PCAP files for further traffic analysis.

The pro version also includes a network traffic filter. This allows users to selectively block network traffic per address per application. This means a user can block an application from communicating with specific servers while still retaining general internet access for that app.

Other pro enhancements include:

• New application notifications that allow users to block or allow an app directly from the notification.
• A network speed graph displayed as a status bar notification.
• Access to five additional application themes in both light and dark versions.

Availability and Distribution

NetGuard is distributed through several channels, including the Google Play Store and the F-Droid Free and Open Source Android App Repository. As of October 14, 2025, version 2.334 was made available.

On the Google Play Store, the application has surpassed 10 million downloads and is maintained by Marcel Bokhorst of FairCode B.V.