Getting Local LAN IP Address with JavaScript: Is It Possible?

WebRTC, an HTML5 extension, has introduced a capability that enables JavaScript to retrieve the local client's IP address. A demonstration can be found at http://net.ipcalf.com.

Contrary to initial assumptions, this feature is intentional and not a bug. However, its potential for abuse raises concerns about its reliability.

Despite these concerns, the ability to expose this data can serve the purpose of informing users about the information their browser may be disclosing. For example, on the website https://www.whatsmyip.org/more-info-about-you/, it provides users with detailed information about their system, including local IP address.

In the past, a Java applet was used for this purpose. However, the increasing reluctance to run applets due to security warnings made this approach less desirable. WebRTC's solution allows for a more unobtrusive method to retrieve local IP addresses.

It's important to note that this approach may not be universally reliable and should be used with caution. Nonetheless, it provides a novel and convenient way to provide users with information about their local network status.