What Is the Great Firewall of China and How Does It Work?

China’s Great Firewall blocks many websites and apps you use every day. If you’re traveling, working, or living in China, losing access to Google, Facebook, and WhatsApp can feel isolating. Even worse, you may not know how this system works or why it’s so hard to get around.

You might also worry about your privacy since the internet in China is heavily monitored. Is your data safe from government monitoring? Do VPNs still work in China? Without clear answers, staying connected and secure can seem impossible. This guide explains how the Great Firewall works and how to stay safe online in China. Editor’s Note: We value our relationship with our readers, and we strive to earn your trust through transparency and integrity. We are in the same ownership group as some of the industry-leading products reviewed on this site: ExpressVPN, Cyberghost, Private Internet Access, and Intego. However, this does not affect our review process, as we adhere to a strict testing methodology.

Quick Summary: What Is the Great Firewall of China

The Great Firewall of China is a government-controlled system that regulates what you can see and do online in China. Its main goal is to block foreign websites and apps, filter content, and enforce strict internet rules. It’s part of a broader strategy to protect the country’s political, social, and cultural values by controlling the flow of information.

This system works using advanced techniques like blocking IP addresses, filtering URLs, and monitoring online activity. It restricts access to platforms like Google, Facebook, and WhatsApp while promoting local alternatives like Baidu and WeChat. For you, this means losing access to many tools and services you rely on every day.

Why Does China Have a Firewall?

China introduced the Great Firewall in the late 1990s as part of its Golden Shield Project. It was designed to control what people in China could see online and ensure the internet aligned with the government’s goals. Over time, it has grown into one of the most advanced and strict censorship systems in the world. Here are some reasons why the firewall exists in China:

• Maintain political control — The Firewall blocks content critical of the Communist Party, including anything about democracy, protests, or human rights.
• Preserve social stability — By filtering out harmful or subversive content, it prevents material that could spark unrest or disrupt public order from spreading online.
• Protect local businesses — Blocking international platforms like Google and Facebook reduces competition and gives Chinese companies like Baidu and WeChat the space to thrive.
• Ensure national security — Controlling the flow of information helps the government guard against foreign influence, cyber threats, and espionage, keeping the state secure.
• Promote Chinese culture — The Firewall filters out content that could push foreign cultural values, ensuring traditional Chinese norms and values remain strong.

How Does the Great Firewall of China Work?

The Great Firewall uses a mix of advanced technologies to block websites, apps, and online tools. Each method targets different parts of your internet activity, making it harder to access restricted content.

Destination IP Address Blocking

The Great Firewall blocks access to certain websites by targeting their IP addresses. Every website you visit has a unique IP address, and the Firewall maintains a list of addresses it wants to block. When you try to connect to a restricted site, your request is stopped before it can reach the destination server.

This method is effective for blocking websites with fixed IPs, like Google or Facebook. However, it struggles with services that use dynamic IPs or Content Delivery Networks (CDNs), as these frequently change their IP addresses. This is why some platforms can still occasionally slip through the cracks.

URL Filtering

The Great Firewall uses URL filtering to block specific web pages based on their address. It scans the URLs you try to access and checks them against a blacklist of restricted keywords or domains. If a URL contains banned words or references a blocked site, the Firewall stops your connection immediately.

This method allows the Firewall to block individual pages without banning an entire website. For example, it can block a single news article while leaving the rest of the site accessible. This level of precision makes URL filtering one of the Firewall’s most effective tools for controlling content.

DNS Poisoning

DNS poisoning, also called DNS spoofing, is one of the most common ways the Great Firewall blocks websites. When you type a web address like google.com, your device asks a DNS server to find the matching IP address. The Firewall steps in, sends back a fake or wrong IP, and stops you from reaching the site.

This method works because it targets a core part of how the internet works. Even if the site isn’t blocked in other ways, DNS poisoning can make it unreachable. You’ll usually see an error message or get redirected to a government warning page.

Deep Packet Inspection

Deep Packet Inspection (DPI) is one of the Great Firewall’s most advanced tools for blocking content. It doesn’t just look at where your data is going — it actually checks the data itself. This means the Firewall can scan for specific keywords, files, or protocols and block them on the spot.

What makes DPI so powerful is how precise it is. It can stop certain websites, apps, or even VPNs if the traffic matches the patterns it’s looking for. For you, this means your online activity is closely monitored, and getting around restrictions becomes much harder.

TCP Reset Attacks

TCP reset attacks are another way the Great Firewall blocks websites. When you try to visit a site, the Firewall sends fake reset signals to your device and the site’s server. This tricks both sides into thinking the connection is closed, so the page won’t load.

This method is sneaky because it doesn’t fully block the website, it just cuts off your access. To you, it might seem like the site is stuck loading or can’t connect, but it’s the Firewall breaking the connection in real-time.

Active Probing

Active probing is how the Great Firewall hunts down VPNs and proxies. When it notices unusual traffic, it sends test signals to the server you’re connecting to. If the server replies in a way that matches a VPN or proxy, the Firewall blocks it.

This method is aggressive because it doesn’t wait for you to make a move—it actively searches for tools people use to bypass it. For you, this means even the most secure VPNs can get detected and blocked in real-time.

Fake SSL Root Certificates

The Great Firewall uses fake SSL root certificates to spy on encrypted connections. Normally, SSL certificates protect your connection and keep it private. But the firewall creates fake ones to trick your browser into thinking the connection is secure while secretly monitoring your activity.

This makes it especially risky to share sensitive information like passwords or personal details online. Since your browser doesn’t alert you, it’s easy to assume your connection is safe when it’s not.

Blocking Access to App Downloads

The Great Firewall also blocks access to app stores and download links for apps that it deems unacceptable. This means you can’t download popular apps like WhatsApp, Instagram, or Signal in China from official platforms like Google Play or the App Store — they won’t appear in the app store.

This restriction forces users to rely on approved Chinese apps or alternative sources, which can be risky. Downloading apps from unofficial sites increases the chance of installing malware or fake versions.

Man-in-the-Middle Attacks

The Great Firewall uses man-in-the-middle (MITM) attacks to intercept and monitor certain types of online activity. When you visit a website, the Firewall can place itself between you and the site, acting like a trusted server. This lets it block, monitor, or even change the data being sent, depending on the connection.

That said, it doesn’t mean all your activity is exposed. Strong encryption, like what secure VPNs use, can protect your data from these attacks. Still, the Firewall’s ability to interfere with some connections makes it important to use reliable tools to keep your privacy intact.

What Websites & Services Does the Great Firewall of China Block?

The Great Firewall blocks some of the most popular websites and apps, including Google and Facebook. If you’re traveling to China, here’s a list of the sites, apps, and services you won’t be able to access.

Search Engines

Social Media Platforms

Messaging Services

News Sites

Streaming & Entertainment

FAQs on the Great Firewall of China

Bottom Line: Is Using the Internet Safe in China?

The Great Firewall controls your entire online experience in China. From social media to messaging apps and even cloud storage, it targets anything that doesn’t fit within the government’s rules. Staying connected can be difficult if you’re not ready for it.

If you’re planning a trip to China, you need to be prepared. Install a trusted VPN that works in China beforehand or use a government-approved one. Also, make sure you have offline backups of anything important.

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Editor's Note: We value our relationship with our readers, and we strive to earn your trust through transparency and integrity. We are in the same ownership group as some of the industry-leading products reviewed on this site: ExpressVPN, Cyberghost, Private Internet Access, and Intego. However, this does not affect our review process, as we adhere to a strict testing methodology.