What are DNS leaks and how to prevent them?

Even when you’re using a VPN, your online activity isn’t always fully private. One of the most overlooked risks to your anonymity is a DNS leak — a silent exposure of the websites you visit. If your DNS requests aren’t properly routed through an encrypted tunnel, third parties (like your Internet Service Provider, or ISP) can still monitor your browsing.

In this guide, we’ll explain what DNS leaks are, how they happen, and how tools like NymVPN can help you browse more securely.

What Is a DNS leak?

Every time you visit a website, your device performs a DNS (Domain Name System) lookup to find the correct IP address. If those DNS requests are sent outside the encrypted VPN tunnel — say, to your ISP’s default DNS server — your internet activity becomes visible again.

A DNS leak happens when your system continues to send DNS queries through the default network, even while a VPN is active.

Why DNS leaks are a privacy problem

DNS leaks reveal which websites you’re visiting — even if the content of the site is encrypted. This kind of metadata can:

• Expose your browsing history to ISPs

• Bypass the protections of your VPN

• Be logged or sold to advertisers

• Be used to profile your behavior

In short: even if your traffic is encrypted, your DNS requests can still betray your intent.

Common causes of DNS leaks

• Misconfigured VPNs: Some VPNs don’t reroute DNS queries properly

• IPv6 traffic: Many VPNs only handle IPv4 and ignore IPv6 DNS traffic

• Smart multi-homed devices: Systems with multiple network interfaces can leak queries

• Browser plugins or apps: Extensions may force requests outside the VPN

Want to browse with real privacy? Try NymVPN to route both traffic and metadata through an anonymous mixnet.

Types of DNS leaks

Understanding the types of DNS leaks can help you better protect against them:

1. Operating system DNS leaks

Occurs when your OS sends DNS requests outside the VPN tunnel due to default settings that override VPN configurations.

2. IPv6 DNS leaks

Some VPNs only handle IPv4, leaving IPv6 requests unprotected and vulnerable to leaks.

3. Transparent DNS proxies

Some ISPs use transparent DNS proxies to intercept DNS requests — even when you try to use a custom DNS. This circumvents standard VPN protections.

4. Browser-based DNS leaks

Browsers like Chrome and Firefox can independently use DNS-over-HTTPS (DoH), bypassing your VPN’s DNS settings.

5. Manual misconfiguration

Manually adjusting DNS settings, installing incompatible software, or using browser extensions can unintentionally bypass the VPN tunnel.

How to Prevent DNS Leaks

1. Use a privacy-first VPN

Many commercial VPNs still use centralized DNS servers or rely on third-party resolvers. NymVPN routes traffic through a decentralized mixnet that anonymizes both your IP address and metadata.

2. Turn off IPv6

If your VPN doesn’t support IPv6, disable it in your network settings to prevent DNS leakage from IPv6 queries.

3. Use encrypted DNS services

Combine VPN use with encrypted DNS (like DNS-over-HTTPS or DNS-over-TLS) to ensure DNS queries are also encrypted end-to-end.

4. Regularly Check for Leaks

While you can’t run a DNS test from Nym yet, you should routinely check your DNS configuration and ensure requests aren’t being routed outside your VPN tunnel.

5. Avoid Browser-Based DNS Settings

Some browsers, like Chrome and Firefox, use their own DNS-over-HTTPS resolvers. This may route DNS requests outside your VPN. Make sure browser settings match your VPN setup.

Using NymVPN to prevent DNS leaks

A DNS leak may sound technical, but the risk is simple: your browsing activity becomes visible. And if your DNS requests go through your ISP, they can see and log every domain you look up.

Most VPNs secure your traffic, but few protect your metadata. NymVPN is built to block surveillance at the network level. It routes your traffic through multiple nodes, breaking the link between sender and receiver — even at the DNS level.

Combined with encrypted DNS practices, this gives you maximum protection against DNS leaks and metadata exposure.

By ensuring DNS queries are anonymized and obfuscated, NymVPN helps keep your intent and behavior private — not just your data.

Use a VPN that doesn’t just encrypt traffic — but defends your metadata too. Download NymVPN and get a network that puts privacy first.

FAQ

What is a DNS leak in simple terms?

A DNS leak occurs when your device sends website lookup requests outside your VPN, revealing the domains you visit.

Can a DNS leak happen without me knowing?

Yes. DNS leaks often go undetected unless you're actively testing or monitoring your DNS requests.

Do all VPNs protect against DNS leaks?

No. Some VPNs don’t reroute DNS traffic properly or don’t encrypt DNS queries, leaving you exposed.

can I test for a DNS leak?

You can use trusted third-party DNS leak test tools online. Nym does not currently offer its own test, but one is in development.

DNS-over-HTTPS enough to stop a DNS leak?

It helps encrypt the DNS request but may still bypass your VPN if not configured correctly. Use both a VPN and encrypted DNS for the best protection.