GFW (Great Firewall of China)
The Great Firewall is the filtering system on mainland China's international internet links that stops people inside China from reaching blocked foreign sites and apps.
Explanation
In depth
Policy is set by the Cyberspace Administration of China, but the government does not publish how the filtering works, so what is known comes from measurements. OONI's 2019 study of Wikipedia found two techniques: forged DNS answers injected on the network, and connections cut after the browser named the site in the TLS handshake (SNI filtering). In July 2020 researchers from GFW Report, iYouPort and the University of Maryland found it dropping TLS connections that used encrypted SNI, the feature designed to hide that name. On 20 August 2025, from 00:34 to 01:48 Beijing time, it injected forged reset packets into every connection on port 443, cutting most HTTPS traffic in and out of China for about 74 minutes. Because it resets connections instead of showing a block page, OONI rarely records a 'confirmed' block in China; the sign is a very low success rate. In OONI tests from China between 15 July and 15 October 2026, YouTube loaded in 3.0% of 2,890 tests and Google in 1.1% of 190, while Bing loaded in 98.9% of 177. Using circumvention tools in China may break local law.
In practice
GFW (Great Firewall of China) in the real world
From AnyProxy's Singapore exit on 15 October 2026, the English Wikipedia article 'Great Firewall' loaded in full and a YouTube video played to the end, two sites that loaded in under 4% of OONI tests from inside China that quarter. Google Search did not work: it showed its 'unusual traffic' reCAPTCHA from both the Singapore and US exits. These tests ran from our exits, not from a Chinese network, and an event like the 20 August 2025 port-443 resets would cut AnyProxy off too.
Sources: OONI - China blocks all language editions of Wikipedia (2019) · Geneva / GFW Report / iYouPort - China is now blocking encrypted SNI (7 Aug 2020) · GFW Report - Unconditional port 443 RST injection, 20 Aug 2025 · Caixin - Apple pulls WhatsApp from China store (19 Apr 2024) · China - AnyProxy country guide (OONI data, 15 Jul-15 Oct 2026)
We checked
Sites the Great Firewall blocks, opened through AnyProxy (15 Oct 2026)
Questions about GFW (Great Firewall of China)
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