Free VPNs hope that you will like their service, want more, and subscribe to their paid plans. So offering the free VPN service is like a marketing expense to them, making the free plan something like a “permanent trial,” like what TunnelBear does. Other free VPNs are ad-supported. While browsing the web through your free VPN, an ad will occasionally pop up. These are often unobtrusive and not really much of a frustration for most people. Some free VPNs may also choose to sell your private data (the same data they are supposed to protect from others who would like to steal it) to advertising agencies or government institutions for financial gain. This may seem unethical, but very often, the terms of use (that you just clicked “I Accept” to) give them full permission to do this.