What is OpenVPN?

OpenVPN, short for Open Virtual Private Network, is an open-source system that creates a private and secure tunnel between networks. The term “OpenVPN” can refer to several related things:

• The open-source OpenVPN protocol used to create encrypted tunnels between networks and establish a VPN connection.
• The OpenVPN software (VPN client) that uses the OpenVPN protocol.
• The OpenVPN company that supports the open-source code and offers its own commercial VPN products.

While the OpenVPN name applies to both the software and the company, the OpenVPN protocol is used in most modern VPN solutions, including NordVPN. Therefore, this article will focus on OpenVPN as a tunneling protocol.

Is OpenVPN safe?

Yes, OpenVPN is one of the safest VPN protocols. It uses secure sockets layer/transport layer security (SSL/TLS) to protect data and relies on the OpenSSL library for further customization, including additional security features.

The OpenVPN protocol supports perfect forward secrecy (PFS), which ensures that past sessions stay protected even if a key is compromised later. It also works with both TCP and UDP connections (more on that below), allowing you to switch to TCP when you want more reliability or to UDP when you need faster speeds.

Because OpenVPN is open-source, its code is transparent. Anyone in the OpenVPN community can look for bugs and suggest fixes. However, this transparency also makes it easier for hackers and security researchers to study the code and look for weaknesses.

OpenVPN supports different cryptographic algorithms and settings, so its security partly depends on the ciphers and key lengths you choose. That’s why proper configuration is crucial, and why choosing a trustworthy VPN service and client is just as important as choosing a secure VPN protocol.

How does OpenVPN work?

OpenVPN creates a secure tunnel for data traffic between the VPN client and the VPN server. This process includes authenticating the client and server, setting up the VPN tunnel, encapsulating and encrypting the data, and finally transmitting the traffic.

OpenVPN supports multiple authentication methods and encryption algorithms and can secure both TCP and UDP traffic. This flexibility makes it a preferred and secure choice for many VPN setups.

1. Authentication

OpenVPN uses various VPN authentication methods to verify the identity of the VPN client and server. These methods usually combine user credentials, digital certificates, and public key infrastructure (PKI) for key management. PKI controls how encryption keys are created, shared, and revoked so that connections stay properly authenticated.

2. Tunnel setup

Once the identities are verified, OpenVPN creates a VPN tunnel between the client and the server. To establish this tunnel, OpenVPN primarily uses SSL/TLS, though it can be configured to use other protocols as well.

3. Encapsulation and encryption

OpenVPN wraps data packets in additional layers to add routing information, identify the source and destination of the data, and apply security measures such as VPN encryption. Encryption ensures that the data passing through the VPN tunnel is hidden from third parties, including your employer, internet service provider (ISP), hackers, and advertising companies.

Another advantage of OpenVPN is its versatility. You can configure it to use different cryptographic algorithms and key lengths. Depending on the setup, it can also work with managed DNS to keep your domain name lookups inside the tunnel, helping prevent DNS leaks. In business environments, administrators can enable data audit logs to track connection activity for security and troubleshooting and apply access control rules to limit which users or devices can access specific resources.

4. Data transmission

Encrypted traffic passes through the VPN tunnel to the VPN server, where it is decrypted and routed to its final destination.

Because the traffic goes through an intermediate server, the destination does not see the original IP address. Instead, it sees the IP address of the VPN server.

Route and policy configuration

OpenVPN controls how traffic moves between the client and the server through VPN routing. When you connect to OpenVPN, the server assigns your device a virtual IP address and creates routing rules that tell your system which data should travel through the encrypted tunnel and which should stay outside it.

Administrators can define routing policies to control this flow. The two main types are full-tunnel and split-tunnel configurations. A full-tunnel policy sends all traffic through the VPN, while a split-tunnel policy only routes specific traffic through it, letting you send part of your online activity through the encrypted tunnel while keeping direct internet access for other apps or services. For example, you can work on VPN-protected files while still reaching your home printer or local websites directly.

What is OpenVPN used for?

OpenVPN is used to create encrypted tunnels for moving traffic between devices and networks over the internet. Individuals and organizations use it to protect data in transit, enable controlled remote access, and connect separate locations.

• Setting up a VPN connection. The main purpose of OpenVPN is to establish a VPN tunnel for secure data transmission. A VPN tunnel is what separates a VPN from a simple proxy, and protocols like OpenVPN make that tunnel possible. You can use OpenVPN any time a VPN connection is needed, such as when accessing a virtual server or creating a private network.
• Encrypting data in transit. In addition to creating an encrypted VPN tunnel, OpenVPN uses cryptographic algorithms to encrypt the data that travels through that tunnel. This makes OpenVPN an excellent choice for sending and receiving sensitive data over the internet, securing VoIP and video conferencing, browsing privately, using public Wi-Fi safely, and protecting the communication of IoT devices.
• Enabling and securing remote access. Because it creates a VPN tunnel and encrypts data in transit, OpenVPN is ideal for enabling and securing remote access to internal networks. Companies, universities, and other institutions can use OpenVPN to manage and control access to their networks from remote locations.
• Linking sites over the internet. OpenVPN can also connect entire networks (site-to-site). Organizations use it to link offices or data centers so teams can share resources and platforms across different locations.

What is the difference between a VPN and OpenVPN?

A VPN is a service that protects your internet connection, while OpenVPN is one of the tunneling protocols a VPN service can use to do that.

Anyone can use the open-source OpenVPN client to set up their own VPN connection. Most VPN providers also include the OpenVPN protocol in their apps. However, OpenVPN is just one tunneling protocol, and a VPN provider can offer several others, such as WireGuard® and IKEv2/IPsec.

What protocol does OpenVPN use?

The OpenVPN protocol is an open-source VPN protocol that uses the OpenSSL library to secure internet traffic by creating a virtual tunnel over UDP or TCP. It is highly configurable, supports both site-to-site and point-to-point connections, and offers strong encryption and authentication options. OpenVPN can tunnel any IP subnetwork and can be configured to use either pre-shared keys or a PKI for authentication. It can also coexist with other VPN protocols, such as IKEv2/IPSec and WireGuard, giving users and providers more flexibility in choosing the best setup for their network.

What are the differences between OpenVPN UDP and OpenVPN TCP?

OpenVPN can run over both TCP and UDP, and most VPN clients allow you to choose which transport protocol to use.

The transmission control protocol (TCP) establishes a connection between the sender and receiver and carefully checks that data packets in transit arrive intact and in order.

The user datagram protocol (UDP) sends data packets without first establishing a formal connection between the sender and receiver. It does not guarantee that packets will arrive or arrive in sequence. This makes UDP faster but less reliable than TCP.

Is OpenVPN better than other VPN protocols?

The answer depends on what you need the VPN protocol for.

OpenVPN is better than outdated VPN protocols like PPTP. In terms of security, OpenVPN is stronger than most other VPN protocols. But security is not the only factor to consider when choosing a VPN protocol.

IKEv2/IPsec, for example, may be a better choice for mobile devices because it handles network changes (like switching from Wi-Fi to mobile data) very well. And if connection speed is your main priority, WireGuard® is much faster than most other VPN protocols. Over the last few years, it has also improved a lot in terms of security, reaching a level comparable to OpenVPN.

What are the pros and cons of OpenVPN?

OpenVPN is a reliable VPN protocol trusted by many, but like most tools, it has its drawbacks. Understanding both its strengths and weaknesses can help you decide whether it fits your needs.

How secure is OpenVPN?

OpenVPN is one of the most secure VPN protocols you can use, as long as it is properly configured and maintained. It uses TLS for key exchange and authentication and supports modern cryptography with certificate-based authentication and PFS.

Because OpenVPN is open-source, the security community can review its code and contribute to keeping the protocol secure.

In practice, OpenVPN can provide strong protection against common network threats and remains a trusted option for both personal and enterprise use. However, how secure OpenVPN is in real-world use depends on how it is deployed and maintained. Server settings, client software, operating system patches, and good credential practices all play a crucial role and should not be ignored.

Is OpenVPN free?

Yes, the OpenVPN protocol is free in the sense that it is open-source and anyone with enough technical skills can modify and use it for their own needs. For example, you could use freely available VPN code to create a VPN server from an old computer.

There is also a free OpenVPN client that you can install and configure to connect to your chosen VPN server, whether it is your own server or VPN servers included with your VPN subscription.

Should you choose OpenVPN?

If you use a premium VPN provider, you can usually choose which VPN protocol to use. So, should you pick OpenVPN if you have that option?

It depends on what you use a VPN for. If you mainly use it for streaming, gaming, or other bandwidth-heavy activities, speed may matter more than maximum security, and no protocol can beat the NordLynx protocol for speed. But if you handle sensitive data and security is your top priority, OpenVPN is a great choice. For the same reason, choose OpenVPN TCP over OpenVPN UDP when reliability and protection are more important than raw speed.

Summary

This blog post offers a concise introduction to OpenVPN, explaining it as a widely used VPN protocol for building secure tunnels and encrypted connections between different networks. It outlines OpenVPN’s core advantages—such as strong security through SSL/TLS, flexibility in using either TCP or UDP transport, and suitability for a range of scenarios from remote access to site‑to‑site networking. The article is presented as a glossary entry and is tagged with key technical terms including “OpenVPN,” “SSL/TLS,” “TCP protocol,” and “UDP protocol,” helping readers quickly understand where and when OpenVPN is an appropriate choice for protecting their online communications.

VPN software works by encrypting your internet traffic and routing it through a remote server before it reaches the website, service, or application you want to use.

There are several types of virtual private networks, but by far the most common are personal VPNs, which anyone can install and use on their own devices.

In this beginner’s guide to VPNs, we’ll explain what a VPN is, how it works, the different types of VPN configurations, and the main benefits and limitations of using a personal VPN.

How Does a VPN Work?

A VPN works by creating an encrypted connection between your device and a remote VPN server. This secure connection is called the VPN tunnel.

Once connected, all the data leaving your device is sent through the VPN tunnel to the VPN server. The VPN server then forwards it to the website you’re visiting, the application you’re using, or the company network you’re accessing remotely.

Data from the website or application then travels back to your device along the same route. It is first sent to the VPN server, which then passes it through the VPN tunnel to your device.

There are five key stages to this process:

1. Handshake & Authentication

The VPN software on your device and the VPN server first authenticate each other. This is known as the VPN handshake.

During the handshake, the VPN client starts a connection to the VPN server, indicating that it wants to create a secure tunnel. The two computers then verify their identities using a password, digital certificate, or another authentication method.

Once authentication is complete, this connection is used to securely exchange an encryption “key” between the client and server. This key is used to encrypt and decrypt data at both ends of the VPN tunnel for the entire browsing session.

EXPERT ADVICE: For fast and secure VPN handshakes, look for VPN services that use the RSA-2048 or RSA-4096 algorithm (not RSA-1024). For extra protection, we also recommend VPN protocols that support Perfect Forward Secrecy.

2. Encryption

With the connection to the VPN server established, the VPN client on your device uses the agreed-upon key and an encryption cipher to encrypt all your internet activity.

In simple terms, this means all the plain-text data from your web traffic is turned into strings of letters and numbers that only someone with the correct decryption key can read.

Web traffic before and after connecting to a VPN with AES-256 encryption.

3. Encapsulation

Your encrypted traffic is then wrapped in an extra layer of unencrypted data that contains information on how to route it to the VPN server. This process is called encapsulation and is handled by dedicated VPN tunneling protocols.

It’s like putting an envelope with a letter inside another envelope with a different address on it. Your actual message is completely hidden from the outside world.

Your VPN client then gives the encapsulated traffic to your ISP, which sends it to the VPN server. Because of the encryption, the only thing the ISP can see is the VPN server’s IP address.

4. Decryption, Forwarding, and Re-Encryption

When the data reaches the VPN server, the outer encapsulation layer is removed, and the original data is decrypted using the encryption key.

This is like opening the outer envelope to reveal the original message inside, giving the VPN server access to the true destination of your connection request.

The server then forwards your request to the website, service, or application you want to reach.

When the web server responds, it sends the data back to the VPN server, where it is encrypted again and sent back through the VPN tunnel until it reaches your device.

The VPN client software on your device then decrypts the data so it can display correctly on your screen.

5. Hash Authentication

As a final protection, the VPN service also uses Secure Hash Algorithms (SHA) to verify the integrity of transmitted data and client-server connections. These checks ensure that no information has been changed in transit between the source and destination.

If the hash value the client generates is different from the hash value the server generated, it means the message has been tampered with and the data is rejected. If the values match, the data is accepted.

NOTE: SHA hash authentication is crucial for preventing man-in-the-middle attacks.

VPN Protocols & Encryption Ciphers

This process can use different protocols and encryption ciphers, depending on the VPN service and how it is configured.

The VPN protocol controls how the VPN tunnel is created, while the encryption cipher is used to encrypt the data that travels through that tunnel.

Depending on the protocol, a VPN can have different speeds, features, and potential vulnerabilities. Most services let you choose which protocol to use in the app settings.

Here’s a quick overview of the most common VPN protocols:

• OpenVPN: Open-source, secure, and compatible with almost all VPN-capable devices.
• WireGuard: Very fast, safe, and data-efficient.
• IKEv2/IPsec: Excellent for mobile VPN users, but may be compromised by the NSA.
• SoftEther: Great for bypassing censorship, but not supported by many VPN services.
• L2TP/IPsec: A slower protocol that is also suspected of being hacked by the NSA.
• SSTP: Deals with firewalls well, but may be vulnerable to man-in-the-middle attacks.
• PPTP: Outdated, insecure, and should be avoided.

The encryption cipher is the algorithm (a set of rules) used to encrypt and decrypt data.

Ciphers are usually paired with a specific key length. In general, the longer the key, the more secure the encryption. For example, AES-256 is considered more secure than AES-128. Where possible, we recommend using a VPN with AES or ChaCha20 encryption.

Four Main Types of VPN Configurations

There are different types of VPN depending on the kind of connection a user needs.

Personal VPN services are designed for everyday internet users who want better online privacy, security, and access. For this reason, they are sometimes called consumer VPNs.

By contrast, remote access VPNs, mobile VPNs, and site-to-site VPNs are all types of business VPN. They are designed to give remote employees secure access to internal company resources.

Below is a quick overview of the four main types of virtual private networks and how they differ:

1. Personal VPN Services

A personal VPN service hides your IP address and browsing history while you use the internet in your free time.

A personal VPN service gives individual users encrypted access to a remote VPN server owned by the VPN provider.

It lets users create a secure connection to servers in many different locations, which they can then use to protect their identity, spoof their geographic location, and avoid surveillance while browsing the internet.

Using Proton VPN, a personal VPN service, on an Android phone.

They can be used on most devices, including iOS and Android smartphones, macOS and Windows computers, and even installed directly on your home Wi-Fi router.

Personal VPNs are the most common type of VPN service, and they are also the type of VPN we focus on here.

2. Remote Access VPNs

Companies use remote access VPNs to keep important information private.

Remote access VPNs give employees encrypted access to a company’s internal network while they work remotely. They are the most common type of business VPN.

Unlike personal VPN services, remote access VPNs are not designed for users who just want to access public online services and applications.

Instead, their purpose is to allow employees to securely access company resources, files, and applications from any location, and to ensure that any company data transmitted is protected from unauthorized access or interception.

Popular examples of remote access VPNs include Access Server by OpenVPN and Cisco AnyConnect.

3. Mobile VPNs

A mobile VPN connection persists even when there’s poor signal.

A mobile VPN is similar to a remote access VPN in that it securely connects remote employees to a company network.

However, while remote access VPNs are designed for users working from a fixed location, mobile VPNs are designed for users who frequently switch between cellular and Wi-Fi networks or whose connection is likely to drop from time to time.

A mobile VPN is built to stay connected despite these interruptions and instability. They are particularly useful for mobile workers, such as firefighters or police officers.

Importantly, mobile VPNs are compatible with any device and any network connection. They are not only for smartphone users.

4. Site-to-Site VPNs

Companies might use site-to-site VPNs if they have offices in different locations.

Site-to-site VPNs are used to securely link a single company network across multiple offices or premises in different physical locations.

They differ from other types of business VPN because they are designed to connect two or more networks together, rather than connecting an individual employee to the office network.

Pros and Cons of Personal VPNs

As mentioned above, at Top10VPN we focus mainly on testing and reviewing personal VPNs. There is still a lot of false or misleading information about what they can and cannot do.

This misinformation makes it harder for beginners to know whether they really need a VPN.

So let’s clarify a few key points. A personal VPN has two primary benefits:

• It hides your IP address and geographic location from the websites, services, and applications you use. Without this information, it becomes much harder to link your online activity to your identity, which in turn makes it more difficult to track, profile, or block you.
• It hides your activity from your ISP or network administrator. Encrypting your data transfers makes it extremely difficult for your ISP, mobile carrier, Wi-Fi administrator, or eavesdroppers on a public Wi-Fi network to see which websites you visit, which files you upload or download, or any personal details you enter into HTTP websites.

Thanks to these two functions, a VPN can be used for various purposes related to better internet privacy, security, and access.

Here are the most popular reasons people use a VPN, based on a survey we conducted in collaboration with GlobalWebIndex:

And the table below summarizes everything you can and can’t do with a VPN:

Summary

The post explains what a VPN is, how it technically works (tunneling, encryption, authentication), outlines main VPN protocols and four configuration types, and clarifies the real benefits and limitations of personal VPNs for privacy, security, and access.