Who runs it
DNS Leak Scan is built and maintained by DEV2REV, a small software company in Porto, Portugal. It is an independent site. No VPN provider owns it or pays for its results.
Why it exists
A VPN can work perfectly and still send your DNS lookups to your internet provider. Most leak tests show a list of resolver addresses and leave you to work out what they mean. This one says in plain words whether the resolvers belong to the same network as your IP address, and what to change if they don't.
How the test works
Your browser looks up a handful of random names on our domain. No resolver has them cached, so the resolver your browser uses has to ask our own DNS server. That server notes the resolver's IP address, and the test page reads the list back.
Each resolver and your IP address are then matched to the network that runs them (its autonomous system number, or ASN), using offline data from iptoasn.com, with an approximate location from DB-IP. The verdict follows fixed rules:
- Can't tell when fewer than half the lookups reach us, or your own network can't be identified.
- Possible leak when any resolver is on a different network from your IP and isn't a well-known public resolver (Cloudflare, Google, Quad9, OpenDNS, AdGuard or NextDNS).
- Can't tell when a resolver's owner can't be identified.
- Looks fine when every resolver is on your IP's network or is a public resolver.
What the test can’t see
- The route between your device and the resolver. A public resolver reached outside the VPN still looks fine here.
- Apps other than your browser, which may use different DNS settings.
- VPNs that run their DNS on a different hosting network from their servers. That shows as a possible leak even when it isn't one.
How the site is paid for
The site is free and shows ads from Google AdSense. Links to VPN services may be affiliate links, which are always labelled and only appear after a result. Neither advertisers nor VPN providers have any say over the test or its verdict. Details are in the privacy policy and affiliate disclosure.
Found a mistake?
If a network owner looks wrong or a verdict doesn't make sense, email hello@dnsleakscan.com or use the contact page. Last reviewed November 2026.