What Is an IP Leak?
An IP leak is any path by which a browser or application exposes the device's real ISP-assigned IP address to a remote server, even though a proxy or VPN is active. The two most common vectors are WebRTC requests and DNS queries, each bypassing the anonymizing layer through different mechanisms. When either succeeds, the destination site sees the true IP alongside, or instead of, the proxy IP, which defeats the purpose of routing through a proxy.
How Does an IP Leak Happen?
IP leaks occur because browsers and operating systems use multiple network channels, and not all of them route through the proxy tunnel automatically.
WebRTC leaks arise at the browser layer. WebRTC establishes peer connections by gathering candidate IP addresses, including the device's real local and public IP. Because these requests happen below the HTTP stack, a misconfigured proxy does not intercept them. WebRTC requests can expose both a user's local and public real IP address even when a VPN or proxy is active, because the requests are made at the browser level and bypass the encrypted tunnel (Security.org, 2025).
DNS leaks occur when the operating system sends domain-resolution queries to the ISP's default resolver instead of routing them through the proxy. A DNS leak exposes the resolver handling domain lookups, which can reveal the user's ISP or country even when the visible HTTP IP belongs to a VPN or proxy. IP-leak tests typically check HTTP, WebRTC, DNS, and IPv6 paths together (Top10VPN (Do I Leak tool), 2025).
IPv6 is a third path. If a proxy only tunnels IPv4 traffic, a site that supports IPv6 can read the device's native IPv6 address directly, bypassing the proxy entirely.
Use Cases
Web scraping and data collection. A scraper that routes requests through a proxy but leaks WebRTC or DNS effectively announces its true origin. Detection engines correlate mismatched IPs and block or fingerprint the client. Proxies that carry DNS through the same egress as HTTP traffic close this gap by design.
Ad verification and brand monitoring. Confirming geo-targeted creatives requires the test request to appear genuinely local. A leak that surfaces a datacenter IP alongside the proxy IP signals an artificial session, causing the ad server to serve a different creative or none at all.
Privacy-sensitive research. Journalists, security researchers, and compliance teams relying on proxies to access region-specific content need origin masking to hold. An IP leak nullifies that protection regardless of the proxy's quality.
Massive's residential proxy network routes HTTP, HTTPS, and SOCKS5 traffic through real consumer devices across 195+ countries. Because DNS resolution travels through the same residential egress as the HTTP request, the DNS-leak vector is closed by design. WebRTC is a browser-level concern; teams typically handle it by disabling WebRTC in the client or using a controlled browser profile that suppresses ICE candidate gathering.
Frequently Asked Questions
A WebRTC leak exposes your IP through the browser's peer-connection mechanism before any HTTP request is made. A DNS leak exposes your identity through misrouted resolver queries. Both bypass an active proxy, but they occur at different layers and require separate fixes.
Use a tool that checks HTTP, WebRTC, DNS, and IPv6 channels at the same time. The Do I Leak checker from Top10VPN reports each channel separately so you can see exactly which path is exposing your real address (Top10VPN (Do I Leak tool), 2025).
A residential proxy that routes DNS through the same egress as HTTP traffic prevents the DNS-leak vector. WebRTC leaks are browser-level and require disabling WebRTC or using a controlled browser environment on the client side. The proxy alone is not sufficient; client configuration matters too.
Most proxy configurations only handle IPv4 traffic. If the client has a native IPv6 address and the target server supports IPv6, the connection can bypass the proxy entirely. The fix is to disable IPv6 at the OS level or confirm that the proxy handles both address families.