The two leaks that cancel out your proxy — WebRTC and DNS

The WebRTC leak

WebRTC is the component that makes video calls work in the browser. To establish a direct connection between two people it needs to know all of the machine's addresses — including the local address and the real public one.

A web page can query that list in three lines of JavaScript. It then obtains your real IP straight past the proxy, with nothing on screen to indicate it.

Check

https://browserleaks.com/webrtc through the configured browser. No public address should match your home connection.

Fix

Browser	Where	Setting
Firefox	about:config	media.peerconnection.enabled → false
Chrome	extension	WebRTC Leak Prevent or equivalent — no native setting
AdsPower	profile sheet	WebRTC → "replace with the proxy IP"
Dolphin{anty}	profile sheet	WebRTC → Altered
BitBrowser	window sheet	WebRTC → proxy / replaced mode

On all three antidetect browsers this is the setting most often left at its default, and the most expensive one to leave at its default.

The DNS leak

Before opening vinted.fr, your machine asks a DNS server: "what is its address?" If that question goes out over your normal connection, two things happen:

1. Your internet provider knows the list of sites you visit, proxy or no proxy.
2. The lookup happens from your country, not from the proxy's France. Some sites serve a different answer depending on where the DNS query came from; the inconsistency is measurable.

Fix

• Firefox: tick Proxy DNS when using SOCKS v5 in the network settings.
• curl: use socks5h:// and not socks5:// — the h means "resolve proxy-side".
• Antidetect browsers: resolution goes through the proxy by default, nothing to do.
• Proxifier: Profile → Name Resolution → tick Resolve hostnames through proxy.

Check

https://dnsleaktest.com → extended test. The servers listed must not belong to your internet provider.

The third, quieter one: the time zone

It is not a network leak, but it reads just as easily. A browser announcing America/New_York behind an Orange France IP is an inconsistency — and unlike the other two, it is visible with no trickery at all, through a single JavaScript call.

Set the time zone from the IP in your antidetect browser. It is a checkbox.

Summary

Leak	Who sees it	Cost to fix
WebRTC	Any web page	One checkbox
DNS	Your internet provider, and sometimes the site	One checkbox
Time zone	Any web page	One checkbox

Three checkboxes. That is the difference between a proxy that protects and a proxy that decorates.

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See also: Checking that your proxy works · HTTP or SOCKS5