What is the Great Firewall of China (GFW)?

The Great Firewall is China's national network infrastructure layer that governs traffic between the Chinese internet and the global internet. It applies IP-based filtering, DNS filtering, deep packet inspection (DPI), and SNI-based TLS filtering to block or restrict access to specific websites and services.

Why is my website accessible in China from some nodes but not others?

Partial accessibility (some China nodes succeed, others fail) indicates the site is "partially reachable" — GFW filtering may be applied inconsistently across different Chinese ISPs (China Telecom, China Unicom, China Mobile), different provinces, or at specific peering points.

Which common services are blocked in China?

Many widely-used international services are not reachable from mainland China, including Google services (Maps, Analytics, Fonts, reCAPTCHA), Meta services (Facebook, Instagram, WhatsApp), X/Twitter, YouTube, and Dropbox. For developers, this means third-party scripts or API calls relying on these services will fail for users in China.

China Firewall Test — Is Your Website Blocked by the GFW?

Status: Enter a domain to begin the test

Accessible

Not Reachable

Error

China Network Reachability Test

Location	Region	HTTP Status	Result	Resolved IP
Enter a domain above to test its reachability from inside mainland China. Examples: google.com github.com check-host.cc

China Network Access — How the GFW Works

China operates a national network infrastructure layer — commonly referred to as the Great Firewall (GFW) — that governs how traffic flows between the Chinese internet and the global internet. Websites and services that are not accessible from within China are subject to various network-level filtering rules. Understanding this is important for developers, businesses, and anyone publishing content for audiences in the Asia-Pacific region.

Network Filtering Techniques

The GFW applies several network-level techniques. IP-based filtering drops traffic to specific server addresses. DNS filtering returns alternative responses for certain domain names, making them unresolvable. Deep Packet Inspection (DPI) examines traffic patterns and can interrupt connections that match specific signatures. SNI-based filtering inspects the TLS handshake hostname and can terminate connections before they are established. These mechanisms may be applied individually or in combination depending on the domain.

What This Test Measures

This tool sends HTTP and DNS probes from real servers physically located inside mainland China and compares the results against a Taiwan reference node — geographically close, but on the open global internet. If China nodes time out or return errors while Taiwan succeeds, the domain is likely subject to network filtering inside China. If both China and Taiwan fail, the origin server may simply be down or unreachable globally. The side-by-side comparison makes it straightforward to distinguish between a global outage and a China-specific reachability issue.

Common Services & Developer Impact

Many widely-used international services are not reachable from mainland China, including Google APIs (Maps, Analytics, Fonts, reCAPTCHA), Meta services (Facebook, Instagram, WhatsApp), Twitter/X, YouTube, GitHub (intermittently), Dropbox, and Slack. For developers, this means that third-party scripts, CDN assets, or API calls relying on these services will silently fail for users in China — even if your own domain is fully reachable. Use this tool to identify which of your dependencies may need a China-compatible alternative.