The first thing to make clear is that proxies are not like VPN (Virtual Private Network), Shadowsocks, or some other Internet censorship circumvention applications. It mainly applies to two situations: 1) users want to hide their real IP address when surfing websites; 2) users want to choose to use the ISP (Internet Service Provider) that supports websites or online games well in order to get a better connection speed. The biggest drawback of proxies is that they are very easy to be invalid, therefore manually and frequently setting up the proxy for a web browser can be a very troublesome matter.

UltraSurf (AKA: 無界瀏覽) is one of the world's most popular free anti-censorship and pro-privacy applications, developed by UltraReach Internet Corporation in 2002. It was originally created to help internet users in Mainland China (where the Internet is heavily censored and Internet users' activities are monitored by the Great Firewall of China) bypass internet censorship and protect their online security & anonymity. After that, it became popular in many countries with Internet blockade due to its good usability, fast running speed and unlimited network traffic.