DNS Blocking Explained in Simple Terms

What Is DNS?

The Domain Name System (DNS) is often described as the phone book of the internet. When you type a website address like example.com, your device asks a DNS server to translate that name into a numerical IP address that computers use to route traffic.

Without DNS, you would need to memorize IP addresses for every website you visit.

How DNS Blocking Works

DNS blocking intercepts these lookup requests. When you try to access a blocked domain:

1. Your device sends a DNS query to a resolver
2. The censor-controlled resolver returns a false response — either an error, a redirect to a warning page, or a sinkhole IP address
3. Your browser cannot reach the intended website

This is one of the simplest and most common censorship techniques because it operates at the infrastructure level, affecting all users on a given network.

Limitations of DNS Blocking

DNS blocking is relatively easy to circumvent with alternative DNS resolvers or encrypted DNS — which is why censors often combine it with IP blocking and deep packet inspection.

Understanding DNS blocking is foundational to understanding Iran internet censorship research.

Safety Note

Circumventing DNS blocking may carry legal risks in some jurisdictions. Users should understand their local laws before attempting any access method. See our safety disclaimer.