Why Websites Block VPNs
VPN blocking has become an arms race. Streaming services block VPNs to enforce geographic licensing agreements. Banks block them to prevent fraud. Schools and workplaces block them to enforce access policies. Government networks block them to control what users can access.
The result: a significant percentage of VPN users have run into a blocked connection, a region-locked error, or a CAPTCHA wall at some point. Understanding how the detection works is the first step to getting around it.
Method 1: IP Address Blacklisting
The most common detection method. VPN providers own large blocks of IP addresses and use them across thousands of servers. Security companies and streaming services maintain databases of known VPN IP ranges and block traffic from those ranges automatically.
MaxMind, IPQualityScore, and IPHub are three commercial providers that sell VPN/proxy detection databases. When you connect through a VPN and visit a major website, there is a reasonable chance your IP is already in one of those databases.
Why it works: most VPN users share IP addresses. If 10,000 users route through the same server, that IP becomes statistically obvious as a VPN exit node.
How to beat it: use a VPN with a large and frequently rotated IP pool. NordVPN, for example, operates thousands of servers and regularly rotates IP ranges. Some providers offer dedicated IP addresses that you alone use, which are much harder to flag as VPN traffic.
Method 2: Port and Protocol Fingerprinting
Standard VPN protocols use well-known ports. OpenVPN defaults to port 1194. WireGuard uses port 51820. L2TP uses ports 1701 and 500. A firewall can be configured to drop traffic on these ports entirely, which blocks the VPN before the connection is established.
Beyond ports, deep packet inspection (DPI) can identify VPN traffic by its signature, even on non-standard ports. Each VPN protocol has a recognizable traffic pattern: the handshake sequence, the header format, the packet timing. A DPI system does not need to decrypt the traffic to identify it as OpenVPN or WireGuard.
Why it works: most VPN users use the default protocol and default port, making their traffic predictable.
How to beat it: use obfuscation (also called stealth mode or scramble). Obfuscated VPN traffic disguises itself as regular HTTPS traffic on port 443, which cannot be blocked without breaking all encrypted web browsing. NordVPN (Obfuscated Servers), ExpressVPN (Lightway with obfuscation), Mullvad (Shadowsocks or VLESS), and ProtonVPN (Stealth protocol) all offer some form of obfuscation.
Method 3: DNS Leak Detection
When you use a VPN, your DNS queries should go through the VPN tunnel. If they leak outside the tunnel and go through your ISP's DNS server, the website can compare your visible IP address to your DNS server location. A mismatch is a strong signal that a VPN is in use.
Some services also check whether the DNS server you are using belongs to a known VPN provider. ProtonVPN and Mullvad run their own DNS servers, and those ranges are sometimes flagged.
Why it works: many VPN clients have historically leaked DNS queries, especially on Windows and Android. Even when the VPN tunnel works perfectly, a DNS leak can expose your real ISP and rough location.
How to beat it: choose a VPN client that routes all DNS traffic through the tunnel by default. Run a DNS leak test at dnsleaktest.com or ipleak.net with your VPN active. If your ISP's DNS servers appear in the results, your VPN is leaking.
Method 4: WebRTC Leak Detection
WebRTC is a browser technology that enables peer-to-peer audio and video. It has a side effect: it can directly query your network interface and expose your real local IP address, regardless of VPN status.
A website can run a WebRTC query in JavaScript and compare the reported IP to your visible connection IP. If they differ, you are using a VPN.
Why it works: WebRTC bypasses the VPN tunnel entirely because it communicates at a lower network level. This is a browser-level leak, not a VPN client failure.
How to beat it: disable WebRTC in your browser. In Firefox, set media.peerconnection.enabled to false in about:config. In Chrome, install an extension like WebRTC Leak Shield. Or use a browser-level VPN or the Tor Browser, which handles this by default.
Method 5: Behavioral and Timing Analysis
Advanced detection systems do not just look at your IP. They analyze request patterns. A single IP address making requests from different countries within minutes is suspicious. A single IP generating unusually high traffic volume is suspicious. An IP that has never been associated with a residential ISP is suspicious.
This approach is less about your specific IP and more about statistical profiling. It is used by financial institutions and fraud detection systems more than by streaming services.
Why it works: VPN exit nodes produce statistical anomalies that residential IPs do not. A residential IP from Germany connecting to a German bank at 9am is normal. A data center IP in Romania connecting to the same bank is not.
How to beat it: residential VPN IPs. Providers like Bright Data, Oxylabs, and some consumer VPNs offer residential proxy networks where your traffic exits through a real home internet connection. These are expensive and sometimes slow, but they are nearly undetectable to behavioral analysis.
Method 6: IPv6 Leaks
Many VPNs tunnel only IPv4 traffic. If your device has an IPv6 address and the website supports IPv6, your real IPv6 address can be exposed even while your IPv4 is protected.
Why it works: IPv4 and IPv6 are separate network stacks. A VPN that only tunnels one of them leaves the other exposed.
How to beat it: use a VPN that explicitly tunnels both IPv4 and IPv6, or disable IPv6 entirely on your device. Verify at ipleak.net that no IPv6 address appears when your VPN is active.
The Netflix Problem (And Why It Is Hard)
Netflix is the most aggressive streamer when it comes to VPN blocking. Their detection combines IP blacklisting, DNS analysis, and a content delivery network that flags mismatched request origins.
When Netflix detects a VPN, it shows error code M7111-5059. The fix is straightforward: switch to a server that Netflix has not blocked yet. The better consumer VPNs (ExpressVPN, NordVPN, Surfshark) maintain servers specifically for Netflix in each region and rotate them continuously as Netflix blocks individual IPs.
The key question when choosing a VPN for streaming is not whether they claim to work with Netflix, but how quickly they update their server pool when Netflix blocks it. Check reviews from the last 30 days, not from two years ago.
Frequently Asked Questions
Can websites tell I'm using a VPN?
Most websites can tell with reasonable confidence. IP blacklist databases cover the majority of commercial VPN exit nodes. A free VPN or a small VPN provider is almost certainly blocked on major streaming sites. A premium VPN with frequent IP rotation is harder to block but not impossible.
Is using a VPN to access geo-blocked content legal?
In most countries, yes. Using a VPN is not illegal in the UK, EU, US, Canada, or Australia. However, bypassing geographic restrictions may violate a service's terms of use. Netflix can terminate your account for using a VPN, though this rarely happens in practice for individual users.
Why does my bank block my VPN?
Banks flag VPN usage as a fraud signal because VPNs hide your real location. If your account is registered in Germany and a login comes through a VPN exit node in Romania, the bank cannot verify where you actually are. This is the same logic that flags card transactions from unexpected countries. Use a dedicated IP or disable the VPN when banking.
Does a VPN with obfuscation always work in China?
Not always. China's Great Firewall updates its DPI rules frequently. What works today may not work in two weeks. Providers with active operations in China or with users there (Mullvad, Astrill) tend to keep their obfuscation working longer than providers who treat China as an afterthought.
What is the most undetectable VPN?
No VPN is completely undetectable. The hardest to detect are those using residential exit IPs with obfuscated traffic. For consumer use, Mullvad with Shadowsocks obfuscation and a low-traffic server is as close as you can get. For professional needs, a privately rented server running your own WireGuard instance with a residential IP is more reliable than any commercial VPN.