For over 20 years, the OpenVPN protocol has been the backbone of the VPN industry. While newer protocols scream about speed, OpenVPN quietly continues to be the only tool that works when governments, ISPs, and strict corporate firewalls try to shut you down.
In this article, we’ll break down how OpenVPN works, examine its security, and explain the difference between OpenVPN TCP vs. UDP to find out why every major VPN provider still includes it in their app.
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How OpenVPN Works and Why It Is Still Essential
While WireGuard forces you to use a specific set of modern tools, OpenVPN is a complex, modular beast built on cryptographic agility. It uses the OpenSSL library, meaning it can be configured to use almost any encryption standard available. Let’s take a look under the hood.
AES-256 encryption
By default, most OpenVPN implementations use AES-256-GCM (Advanced Encryption Standard with 256-bit keys). Why does this matter?
- Military-grade: This is the same encryption standard used by the NSA, banks, and military organizations to secure Top Secret data.
- Hardware acceleration: Unlike WireGuard’s ChaCha20 (which is fast in software), AES benefits from AES-NI instructions built directly into modern Intel and AMD processors. This means that on a desktop or laptop, OpenVPN can actually be incredibly fast because the CPU has a dedicated physical pathway just for crunching these numbers.
Data authentication
Encryption hides your data, but authentication ensures no one tampered with it along the way. OpenVPN uses strictly defined HMAC (Hash-based Message Authentication Code) to verify every single data packet. Before your computer accepts a packet from the VPN server, it runs a mathematical check (using algorithms like SHA-256 or SHA-512) to ensure the data wasn’t altered in transit by a hacker or a government firewall.
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The “chatty” connection
Here is the biggest difference from WireGuard. WireGuard is stateless (silent when not used), but OpenVPN is stateful. It constantly sends small “keepalive” packets back and forth between your device and the server.
- The downside: This “chatter” prevents your phone’s radio from going to sleep, which drains the battery faster than WireGuard.
- The upside: It provides immediate feedback. If the connection drops or hangs, OpenVPN knows instantly and can trigger a kill switch or attempt to reconnect, providing a layer of stability that is critical for sensitive connections.
The OpenVPN longevity secret
OpenVPN is the “Swiss Army Knife” of VPN protocols. Launched in 2001, it has survived two decades of the internet’s evolution. Unlike proprietary protocols hidden behind closed doors, OpenVPN is open-source. This means its code has been dissected, audited, and stress-tested by more security researchers than any other protocol in history.
And even though OpenVPN security news can occasionally highlight its vulnerabilities, this is actually a strength. Because the code is open and widely scrutinized, bugs are found and patched publicly—often before bad actors can exploit them. It is “proven” in a way that newer code simply cannot be yet.
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OpenVPN UDP vs. TCP: The Most Important Setting
When you open your VPN app settings, most of them offer you a choice: OpenVPN TCP or UDP. Cryptic as it may seem, it is actually the single most important switch for your connection’s performance and stability.
UDP (User Datagram Protocol)
- Best for: Streaming, gaming, torrenting, VoIP.
- The vibe: “Fire and forget.”
UDP is the default mode for a reason. It shoots data packets at the server without waiting for confirmation that they arrived. If a packet gets lost, who cares? It just keeps sending. This makes OpenVPN UDP significantly faster and ideal for streaming Netflix or hopping on a Zoom call where a microstutter is better than a 5-second lag.
TCP (Transmission Control Protocol)
- Best for: Bypassing censorship, browsing, unstable Wi-Fi.
- The vibe: “Trust but verify.”
TCP is the perfectionist. It numbers every single packet and demands a receipt. If a packet goes missing, TCP stops the line and resends it. This constant back-and-forth checking makes OpenVPN TCP slower, but it guarantees that your data arrives intact.
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The killer feature: Port 443
So, with such a clear OpenVPN TCP vs. UDP performance gap, why would anyone choose the slower TCP option? Because of one specific trick: port 443.
Port 443 is the standard port for HTTPS traffic—the secure web traffic you use to bank, shop, and browse. If a network administrator or a government censor blocks port 443, they effectively break the internet.
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When you run OpenVPN TCP over port 443, your VPN traffic looks exactly like regular HTTPS traffic. Deep packet inspection (DPI) tools have a much harder time distinguishing your VPN tunnel from a user simply browsing Wikipedia. This is why OpenVPN works in university libraries, corporate offices, and restrictive countries where WireGuard often fails.
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So what should you choose, OpenVPN UDP or TCP? For speed, prefer UDP. For reliability—definitely TCP.
When to Use OpenVPN Over WireGuard
While WireGuard can be your daily driver for most cases, OpenVPN still shines bright in these two specific scenarios:
When you need to bypass censorship
If you are in China, Russia, or the Middle East, the OpenVPN protocol (specifically via TCP) is your best friend. Its ability to blend in with normal web traffic is unmatched. WireGuard is too “noisy” and easy to spot by sophisticated firewalls.
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When your internet is unstable
If you are on spotty public Wi-Fi or a mobile connection that keeps dropping packets, OpenVPN TCP offers better error correction. It will fight to keep your tunnel alive even when the underlying signal is weak.
OpenVPN Pros and Cons
Is it perfect? No. Is it necessary? Absolutely.
| ✅ The pros | ❌ The cons |
|---|---|
| ✔️Unmatched compatibility: Works on almost any device, router, or operating system. | ➖The “bloat”: The codebase is massive (hundreds of thousands of lines), making it heavier than modern alternatives. |
| ✔️Firewall busting: OpenVPN TCP gives you a stealth mode that other protocols lack. | ➖Speed: Generally slower than WireGuard, especially on mobile devices. |
| ✔️Proven security: Two decades of audits, which means fewer nasty surprises. | ➖Latency: OpenVPN TCP can introduce lag that kills gaming performance. |
Why the OpenVPN Protocol Isn’t Going Anywhere
In a world obsessed with speed, it is easy to look at WireGuard and declare OpenVPN obsolete. But that would be a mistake.
OpenVPN remains the “heavy lifter” of the privacy world. While it may not match the raw throughput of modern protocols, the OpenVPN TCP vs. UDP toggle offers something arguably more valuable: flexibility.
OpenVPN UDP allows you to maintain the speed necessary for most everyday tasks, while TCP is unbeatable at breaking through strict corporate firewalls and evading censorship in restrictive regimes. This freedom of choice gives you the control you need to stay connected when everything else fails.
And as long as governments try to block access and networks try to throttle traffic, OpenVPN’s ability to shapeshift and blend in will keep it on the throne for years to come.
FAQs
What is OpenVPN TCP?
It is simply the OpenVPN protocol running over a Transmission Control Protocol tunnel. Think of it as sending your data via Certified Mail where every letter must be signed for. It’s slower than UDP, but it ensures nothing gets lost and looks like regular secure web traffic to outsiders.
Does OpenVPN work in China?
Yes, but you usually need to configure it correctly. OpenVPN in China faces the Great Firewall, which actively hunts for VPNs. Using OpenVPN over TCP (port 443) is often the only way to get through, though many providers now add an extra layer of obfuscation (like Scramble or XOR) on top of OpenVPN to hide it further.
Is OpenVPN blocked in China?
The protocol is targeted, yes. Standard OpenVPN UDP connections are often blocked immediately. However, because of OpenVPN TCP’s flexibility that allows it to disguise itself as normal web traffic, it is practically impossible to block the protocol completely.
What is the OpenVPN TCP vs. UDP difference for gaming?
When faced with the TCP vs. UDP OpenVPN choice for gaming, always prefer UDP. The OpenVPN TCP vs. UDP speed difference is massive. TCP’s error checking creates latency spikes every time a packet is lost. UDP ignores lost packets, keeping your ping low and your gameplay smooth.
Should I use an OpenVPN server TCP or UDP?
As a general rule, when choosing between an OpenVPN TCP or UDP server, set it to UDP first. It gives you the best balance of speed and security. Only switch to TCP if the UDP connection fails or if you are on a restricted network that blocks non-web ports.
