Once you turn on a proxy or VPN, it's easy to assume all of your network traffic is now fully hidden. But there's a step that gets overlooked constantly: DNS lookups. If DNS queries don't route through the proxy tunnel, your real network location can still leak — even while your IP shows the proxy's address. This is what's known as a DNS leak.
What DNS is, and why it becomes a weak point
Every time you visit a website, your device first has to resolve the domain name (like www.example.com) into an IP address — that's a DNS query. Normally, if you're using a VPN, DNS queries should also travel through the VPN's encrypted tunnel and get resolved by the DNS server the VPN specifies.
But if the system or software isn't configured correctly, DNS queries can bypass the VPN tunnel entirely and go straight to your local ISP's DNS server. That means even though your web traffic is routed through the proxy IP, your DNS requests reveal your actual ISP and rough geographic location — that's a DNS leak.
Common causes
- Incomplete VPN configuration — some VPN clients don't force the system's DNS settings by default, so the OS keeps using the ISP-assigned DNS
- IPv6 traffic not covered by the proxy — many VPNs only handle IPv4 traffic; if a device also has IPv6 enabled and DNS resolves over IPv6, it can bypass the VPN entirely
- Browser-level DNS features — some browsers have their own DNS-over-HTTPS settings, which can conflict with system-level VPN configuration and cause inconsistent resolution paths
- Gaps in transparent proxy or system-wide settings — some proxy software only handles traffic from specific apps, leaving other apps or system processes to resolve DNS through a different path
How to self-check for a DNS leak
The most direct method: with the VPN or proxy turned on, check which DNS server is currently being used, and whether it matches your VPN provider. If the DNS server's operator matches your local ISP (the same one you'd see without the VPN on), that's a strong sign the DNS queries aren't going through the VPN tunnel — a leak.
The ipscoper environment check tool shows your current DNS resolution info alongside your IP lookup results, so you can compare the two directly. If the IP shows the proxy's region but the DNS server shows your local ISP, that's about as clear a confirmation of a DNS leak as you'll get.
This follows the same logic covered in WebRTC Leaks: How They Work, the Risks, and How to Self-Check: a proxy only guarantees that the network-layer IP gets swapped — it doesn't guarantee every related request travels through the same tunnel. DNS and WebRTC are the two pieces most commonly left exposed.
How to fix it
- Check whether your VPN client supports DNS leak protection — most mainstream VPN services have a dedicated "DNS leak protection" toggle in settings; make sure it's on
- Manually specify a DNS server — if the VPN doesn't force DNS settings, you can manually point your system's network settings to the VPN's DNS address
- Watch your IPv6 settings — if the VPN doesn't proxy IPv6, consider temporarily disabling IPv6 at the system level to close off that path
Takeaway
DNS leaks and WebRTC leaks are two versions of the same underlying problem — some part of a network request bypasses the proxy tunnel and exposes information that was supposed to stay hidden. Running an environment check periodically is a far more proactive habit than only discovering the issue after an account already looks abnormal.