What does the Great Firewall of China mean for your website?

Several explainers we read on the Great Firewall come from VPN sellers, and they speak to people trying to get past it. This guide doesn’t. It’s for someone with a different problem: a website.

What you need to know is narrower. Could it block your site, and what else could look like a block? This is part of our guide to putting your website in China.

What is the Great Firewall of China?

The Great Firewall is a set of filters on traffic entering and leaving mainland China. The name, a play on the Great Wall, appeared in print in 1997. The project began in 1998, and its first phase finished in 2006.¹

• Who runs it: Wikipedia names the Cyberspace Administration of China, since 2013.¹
• What it covers: the mainland. Proton notes it doesn’t cover Hong Kong or Macau.²
• What’s public: very little. No official report on its design has ever been published, wrote the authors of GFWeb.³

The closest legal text we found is the Cybersecurity Law. Article 50 of its 2016 version has authorities notify the bodies concerned to block banned information from abroad by technical means.⁴

That law was amended with effect from January 1, 2026, and the articles were renumbered.⁵ We haven’t verified the current number.

So almost everything known comes from outside measurement, plus one large leak.

In September 2025, about 600 GB of files linked to the firewall’s research side appeared online.⁶ Treat its contents as reported, not proven.

How does it decide what to block?

It looks for a name, an address or a keyword at several points in a connection. Researchers describe DNS as the first filter, followed by HTTP and HTTPS filters.³ Each one keeps its own list.³

1. DNS lookup

   Domain name

2. Connection

   IP address

3. TLS handshake

   Name in the SNI field

4. Page request

   URL, and content if HTTP

A filter can cut at each stage.

Filter	What it reads	What it does	What it means for your site
DNS	The domain being looked up	Returns a fake IP 37	The browser goes to the wrong address, and the page usually doesn’t load
IP	The server address	Blocks the address 38	Other sites on your IP may matter
HTTP	The full request, down to URL keywords 3	Resets the connection 3	Plain HTTP pages are fully readable
HTTPS	The hostname in the SNI field 3	Resets the connection 3	Your content stays unread, your domain name doesn’t
QUIC	Hostnames, after decrypting Initial packets 9	Blocks, from a separate list 9	HTTP/3 can behave differently from HTTPS

QUIC filtering dates from April 7, 2024.⁹ So a test from 2023 may no longer describe what happens today.

The filters can also hit the wrong target. In 2020, about 41,000 of the 311,000 domains on the DNS list were caught only for containing a blocked string.¹⁰

A rule for torproject.org also hit mentorproject.org.³

GFWeb found in 2024 that this had been largely fixed, though not fully.³

IP blocking is the bigger unknown. A 2019 study found 39,787 sites blocked by IP in the Alexa top million, many of them likely collateral damage.⁸ We found no current figure. See whether a shared IP can get your site blocked.

Will your website be blocked?

Probably not, on the numbers, but nobody can promise that. We set each study’s blocked domains against what it tested. The shares below are our own arithmetic, not the researchers’ findings.

Study	Domains blocked	Domains tested	Share
GFWatch, DNS filter, April to December 2020 10	About 311,000	534 million distinct	About 0.06%
GFWeb, HTTP filter, February 2022 to September 2023 3	943,000 pay-level domains	694 million pay-level domains	About 0.14%
Wu et al., 2023 to 2025 11	741,542, cumulative	227 million per week	About 0.33%
Wu et al., top 1 million sites, Great Firewall 11	25,441, at least once	1 million	About 2.5%
Wu et al., top 1 million sites, Henan firewall 11	175,925, at least once	1 million	About 17.6%

The last two rows are the ones to read. Huge test sets likely include many domains few people visit, and the share among popular sites is higher.

Even so, about 97.5% of that top million were never blocked by the national firewall in the study. Henan is the exception, and it needs its own explanation.

The national list isn’t the only one. The Wu study found Henan province filtering traffic leaving the province, with 4,196,532 domains cumulatively.¹¹

That’s more than five times the national total, and ten times at some moments.¹¹ It tested one Henan provider, and six other regions showed nothing.¹¹ So a site could fail in Henan alone, which is our inference. We found nothing on Henan after that study.

Don’t count on a national block passing, either. More than half of the domains the Great Firewall ever blocked stayed blocked for all 256 days measured, and the mean was 173.8 days.¹¹

Henan’s blocks were shorter, with a mean of 35.7 days.¹¹ Those are study figures, not a forecast for your domain.

If you want the reasons behind a block, read why websites get blocked in China.

Is the firewall why your site is slow?

Nobody has shown how much of it is. Slowness is a separate problem from blocking, and the main study on it leaves the cause open.

A 2020 study measured traffic into mainland China. The slowdown affected 79% of the pairs it measured, and more than 70% of pairs fell below 1 Mbps for more than 5 hours a day.¹³ Top Alexa sites hosted abroad did no better.¹³

In a one-day test, firewall hops matched the bottleneck hops in 34.45% of cases.¹³ The authors call that a clue the firewall may not be the cause, but they tested only nodes that inject resets, so other firewall devices could be involved.¹³

They put forward two explanations, and say pinning it down would take insider knowledge:¹³

• Government policy, which could include discouraging access to foreign services.
• Financial motives at Chinese providers.

That study is from 2020, and we found no independent repeat of it. The daily pattern it found still gives you a simple clue: test at more than one time of day.

What you’ll see from China, and what it means

The same complaint, “my site doesn’t work in China”, can have six different causes. Only one of them is a national block.

What you see	Likely explanation	Evidence
Fails on repeated tests from many places	Possible national block	Needs several probes over time 12
Loads, but badly at certain hours	Congestion-like slowdown, cause unsettled	Daily pattern in 2020 13
Page loads, but maps, forms or video are missing	Blocked third-party service	http://www.google.com failed 10 of 10 tests 17
Fails from one location only	Local interference	Provincial, provider or cloud filtering 311
Everything fails for about an hour	A wider disruption	August 20, 2025 incident 15
A page warns about an ICP	Your host, not the firewall	Mainland cloud redirects 3

Two of these deserve a closer look.

The outage. On August 20, 2025, connections on port 443 were reset for about 74 minutes, whatever site they were headed for.¹⁵

GFW Report says the cause was a new device or a known one misbehaving.¹⁵ Freedom House says it was likely a misconfiguration.¹⁶ An outage like this isn’t a block on your site.

The third-party failure. Your own domain may be fine while your page waits on something blocked.

In one AppInChina test, a failed analytics call took over 3 minutes, in a page load of about 5 minutes.¹⁸

That’s one vendor’s test, but it shows why a clean domain check proves little. See which Google services fail in China.

To tell these apart, follow our guide to whether your site is blocked or just slow.

Free check

Is your website visible on Baidu?

Enter your website. We check Baidu, access from China and how your site is set up, then email you the report.

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Does it stop Chinese search engines from reaching you?

We found no published measurement, only an old statement from Baidu. It matters, since Baidu has to fetch your pages before it can show them.

Baidu’s 2014 guide says its crawler servers are in China, and that what ordinary users there can’t reach, Baiduspider can’t reach either.²⁷ It doesn’t mention blocked sites as such, and we don’t know if it still holds.

Our guide to whether Baidu indexes foreign websites covers what is known.

Can you find out why, or get unblocked?

We found no procedure for either. Here is where the evidence stops:

• No official list found. The lists in this guide are rebuilt by researchers through testing.³
• No published criteria. China Briefing wrote in 2017 that there are “no formal criteria” for when a site gets banned.¹⁹
• No notice. We found no source describing a notification to site owners.
• No formal appeal. China Briefing wrote in 2017 that none exists.¹⁹ We found nothing newer.

Absence of a source isn’t proof that nothing exists. If a block is costing you real business, ask a local adviser.

Changing hosts is often the first idea, and it may not help. A new host changes your IP, while DNS, HTTP and HTTPS filters work on your domain name.³

A test of a URL doesn’t always show which filter applies, so a move can be a costly guess.

What should you do about it?

Treat the firewall as a condition to work within, not an obstacle to beat. Here are five steps.

1. Test from inside China. Use several probes, at several times, on your exact URLs. GreatFire notes that blocking applies per address, not per site.¹² See how to test your site from China.
2. Remove blocked dependencies. Anything your page calls from a blocked service can fail, and you control that list.
3. Choose your hosting for speed. Hosting abroad can still mean slow or blocked pages,²⁰ and mainland hosting has its own conditions. Compare your hosting options in China.
4. Review sensitive content with an adviser. China’s rules list banned categories,²⁵ and how they reach a foreign site is a legal question. Start with sensitive content on a Chinese website.
5. Retest on a schedule. Filters change, as QUIC showed in 2024.⁹ One clean result won’t stay true forever.

The bottom line

If you only remember one thing: the Great Firewall is a real risk, but rarely the first problem.

Most domains tested aren’t on its lists, while slow delivery was widespread in the one large study of it. Blocked add-ons can break a page that isn’t blocked itself.

Test your actual pages from China before you draw any conclusion.

How Index in China can help

We localize your site into Simplified Chinese, with a person reviewing every page, then work on getting it indexed on Chinese search engines.

We don’t help anyone get around the firewall, and we can’t get a site unblocked. If your case needs a local adviser, we’ll say so. Book a 30-minute call.

Book a 30-minute call

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