What is Tunnelblick?
It does this by creating a "Virtual Private Network", or "VPN" to the OpenVPN server using a program named "OpenVPN", which is included within the Tunnelblick application. When you connect through a VPN, your computer sends some or all network traffic through a "tunnel" to the VPN server, which then passes on your network traffic to a local network or the Internet. It is as if you were connecting to the network or Internet through the VPN server instead of your computer. Normally, all traffic between your computer and the VPN server is encrypted.
VPNs are primarily used for three purposes (sometimes all three simultaneously):
In addition to Tunnelblick, you need access to a VPN server. Your company may provide one, or you can obtain VPN service from any of several VPN service providers, or you can use another one of your computers or a router to act as a VPN server. See Getting VPN Service for details.
It runs on OS X 10.7 through 10.11 ("Lion", "Mountain Lion", "Mavericks", "Yosemite", and "El Capitan") and macOS 10.12 ("Sierra"). It comes as a ready-to-use Universal application with all necessary binaries and drivers (including OpenVPN and tun/tap) included. No additional installation is necessary — just add your configuration and encryption information.
Tunnelblick is free software licensed under the GNU General Public License (GPL) Version 2.