Surfboard is a network debug tool designed for the Android platform. With this app, users can redirect specific network traffic to various proxy types such as HTTP, HTTPS, SOCKS5, SOCKS5-TLS, Shadowsocks, Vmess, and Trojan. It offers a range of features for network debugging and customization.

One of the key functionalities of Surfboard is its ability to intercept system traffic using the VpnService API. This allows the app to forward, modify, block, and process network traffic as needed. To ensure user control, Surfboard provides bypass settings that allow users to restrict specific app traffic from going through the VPN interface.

Please note that Surfboard is available for free on the Android platform and falls under the Utilities & Tools category.