A DNS leak happens when your device sends DNS queries through your ISP's resolver instead of the VPN tunnel — exposing every website you visit even though your traffic is encrypted.

How does this DNS leak test work?

We trigger DNS lookups for unique subdomains and ask an authoritative server which resolvers asked for them. The resolvers returned are the real DNS servers your device is using.

How do I fix a DNS leak?

Enable your VPN's built-in DNS leak protection, disable IPv6 if your VPN doesn't tunnel it, and turn off Windows' Smart Multi-Homed Name Resolution.

DNS Leak Test — Free Online Network Tool

What is a DNS leak?

Every time you visit a website, your device asks a DNS server to translate the domain name into an IP address. A DNS leak happens when those queries bypass your VPN tunnel and go straight to your ISP's resolver — meaning your ISP (and anyone monitoring it) can still see every site you visit, even though your traffic is encrypted.

Why DNS leaks happen

IPv6 not tunneled — your VPN only routes IPv4, so IPv6 DNS queries leak.

Windows Smart Multi-Homed Name Resolution sends queries to every available interface in parallel.

Transparent DNS proxies at the ISP intercept port 53 regardless of which resolver you configure.

Misconfigured VPN client without built-in DNS leak protection.

About this DNS Leak Test

Run a quick DNS leak test that resolves multiple randomized subdomains and shows every resolver that answered — the safe result is your VPN's DNS, not your ISP.

How to use DNS Leak Test

Enter the target

Type or paste the target you want to inspect into the input field at the top of the page.

Run the Check

Click the check button — the tool queries live data sources and returns results in seconds.

Read the Report

Review each finding: status, score, and the reason behind every warning are listed line by line.

Act on the Findings

Follow the linked remediation guides to fix issues, or copy the report to share with your team.

Why Use DNS Leak Test

When something in your stack misbehaves, half the battle is figuring out whether the problem is you, the network, or the other side. DNS Leak Test gives you a fast, opinionated readout so you can rule things in and out in seconds. Because the check runs on live infrastructure and reports raw results — not marketing-safe summaries — you can trust what you see and act on it. Toolzer's design philosophy is simple: privacy-first (no tracking, no accounts), performance-first (the page is interactive in under a second on a 3G connection), and honesty-first (no fake ratings, no dark patterns, no upsells). DNS Leak Test follows the same rules as every other utility on the site. You can bookmark this page, share the URL with a colleague, or pin it to your browser's toolbar — the experience will be identical every visit, and it will keep working even if you're on airplane Wi-Fi. Real people use this tool for real work — freelancers cleaning up client deliverables, sysadmins triaging tickets, students finishing assignments — and it is tuned for those workflows, not for demo videos.

Tips & Best Practices

1Run the check from more than one network (mobile hotspot vs office) to distinguish a real outage from a local DNS issue.

2Save the full report with a timestamp — it is invaluable evidence when opening a support ticket with a provider.

3Re-run the check after every fix so you have a clean 'before / after' record.

4Cross-reference results with a second, independent tool when the stakes are high — no single source is perfect.

5If the check surfaces a warning you don't understand, read the linked docs before applying a 'fix' someone suggested online.

Common Use Cases

1Diagnosing a slow or unreachable website before opening a support ticket with your ISP or hosting provider using DNS Leak Test.

2Verifying that a newly configured DNS, firewall, or VPN rule actually took effect from the public internet.

3Auditing a client's infrastructure during a freelance networking or security engagement.

4Teaching students or junior admins how core internet plumbing (IP, DNS, routing) works with a live example.

5Sharing precise technical evidence (IP, hostname, response times) with a remote colleague inside a chat message.

Frequently asked questions

Is this tool free to use?

Yes — every Toolzer utility is free, requires no signup, and runs in your browser.

Is my data private?

Yes. Calculations happen locally in your browser; nothing is uploaded or stored.

Do I need to create an account to use Toolzer?

No. Every utility on Toolzer is free, anonymous, and works in any modern browser without registration.

Is Toolzer safe to use with sensitive inputs?

Yes. Whenever the tool can produce an answer entirely in the browser, the data never leaves your device.

Does Toolzer work on mobile?

Yes. The interface is fully responsive and works on iOS Safari, Android Chrome, and every modern mobile browser.

Can I link to or bookmark a result?

Yes. Every Toolzer page has a clean permanent URL you can bookmark or share.