VPN Master is a subscription-based VPN extension designed for Firefox, focusing on web development needs. It utilizes two free proxy providers to enable users to select from HTTP, SOCKS4, and SOCKS5 servers. The extension intelligently validates connectivity and automatically resets the proxy if the connection is unstable, ensuring a reliable browsing experience.

The application offers various customizable options, including support for GET and POST requests, cookies, referer and user-agent headers, HTTPS, and anonymity levels. Additionally, it features built-in tools for checking DNS leakage and external IP addresses, making it a comprehensive solution for developers and IT professionals seeking to enhance their online privacy and security.