Using a VPN is a great way to increase your privacy while online: sites you visit won't be able to identify you by your IP address, meaning you can make it so you're in a different country. However, you may find yourself wondering whether or not your ISP can see that you're using a VPN, and, if so, whether that matters.

This Cybersecurity Awareness Week article is brought to you in association with Incogni.

Can My ISP See If I'm Using a VPN?

The answer to the first part is simple: Yes, your ISP could determine that you're using a VPN if it wanted to.

This is due to the way a VPN works: When you use the internet without a VPN, you connect from your computer to your ISP's system, which in turn connects to the site you want to visit — it's a tiny bit more complicated than that, but for our purposes it's enough.

When you connect through a VPN, you go from your ISP to the VPN service's server and then to a site. This makes it appear to that site like you're using the IP address of the VPN server, and hopefully fooling them into thinking you're somebody else, somewhere else. Note, though, that without incognito mode engaged, you could still be very easily identified.

What Does My ISP See?

VPNs are different from proxies in that they encrypt your connection through what's called a secure tunnel. This encrypts the connection from your computer to the VPN's server, usually using an advanced encryption method like AES-256 that can, in theory, only be cracked by somebody with a few billion years to spare.

The tunnel makes it so the site you visit can only see your fake IP address (the VPN's IP address), but it also works the other way around. When an ISP looks at the connection you made and requests to know where it's headed, all it gets back is some random garbage. It can see that you're making a connection — it can even figure out the IP address you're connecting to — but nothing beyond that.

Of course, getting back random garbage is a tell-tale sign that a VPN is being used. An ISP can figure out pretty easily which connections lead to a VPN: just look at the ones sending a lot of encrypted data back. There's just no realistic way to figure out which VPN — not without finding out from the people renting out the server space, and they'll never tell — or what you are accessing through a VPN.

While your ISP will not be able to directly see what you're doing, they may be able to make an educated guess about some activities based on your data use patterns. But how? Let's use an analogy.

Suppose that you were able to monitor all of the water going into a house or apartment. You don't know anything about what is in the house. At 6:50 in the morning, you notice that something in the house has used 2.6 gallons of water, and then a few minutes later, you notice the house consuming 2.5 gallons per minute continously for 10 minutes. Even knowing nothing about what is in the house, you can very reasonable guess would be that someone flushed a toilet, and then took a 10 minute shower as part of their morning routine.

Similar methods of analyzing how much data you use, when you use it, and the timing of the data use can provide insight into what you're doing, even if it isn't directly observable.

Do ISPs Care If You Use a VPN?

That leads to the second part of the question, whether ISPs care that you're using a VPN. The answer is probably that it depends on your geographical location. In most of the world, we can assume that ISPs generally don't care. Whether you connect to a VPN's server or that of a random site is probably all the same to them. After all, many people use VPNs to remotely connect to work networks. A VPN you're using for privacy looks about the same.

There is, however, one big exception to this rule: Dictatorships like China, Iran, and a bunch of other countries that have made VPNs illegal. In those countries, most ISPs will either be owned by the state or have some kind of state control imposed, meaning that there is a chance of somebody checking on connections.

We know that the Chinese authorities will impose fines on VPN use, and there are rumors that the government has developed VPN-tracking technology. We can speculate that these programs can gather information on which connections are sending back encrypted data and thus identify them, but we're not sure.

VyprVPN is one VPN service that claims to have connection protocols that can fool the Chinese detection system, we assume by making the VPN tunnel look like a regular connection somehow.

What About ISPs That Sell Data?

Another set of countries where ISPs may not be so happy about customers using VPNs are ones where it's legal for them to track and sell user data, like in the United States. Though we have no evidence of this, we can imagine that ISPs aren't too happy with VPN users since that means there's a lot less information to sell.

However, since VPN use is legal in the U.S. and there's no way to mandate how people can use their internet connection, there's little ISPs can do to stop customers who choose to use a VPN.

Whatever the case may be, it may be a smart move to use a VPN and deny your ISP the chance to harvest your data. We've put together a guide to finding the best VPN out there, but if you want a shortcut, we recommend ExpressVPN for most people, most of the time.