The Outline Server acts as a proxy and relays connections between the client and the sites they want to access. It is based on Shadowsocks, and offers a REST API for management of the server by the Outline Manager application.
Outline is not a true VPN solution but rather a Shadowsocks-based proxy. The two technologies are similar in the way they can be used to redirect network traffic and make it appear as originating from another device (the server), and hide the traffic's final destination from observers and filters until it reaches the proxy server. However, a VPN has additional capabilities, such as encapsulating traffic within a virtual tunnel, and allowing connected devices to "see" each other (as if they were connected to a LAN).
In March 2018, Max Eddy of PCMag stated that a preview version of Outline VPN was "startlingly easy to use" and "removes privacy concerns associated with VPN companies". However, Eddy criticized the software for not encrypting all traffic on Windows, and warned users that "individual use may lack some anonymity compared [to] large VPN companies".[9]
Since version 1.2, the Outline Windows client came out of 'Beta', effectively beginning to encrypt all traffic from the device, on par with the Outline clients for macOS, ChromeOS, Android, and iOS.