A web proxy is a website that acts as an intermediary between a website visitor and the website that they are visiting. Requests for web pages and other data that are sent to the target website are routed through the web proxy, with any data that may identify the website visitor obscured. The web page data and other data that is returned by the target website is also routed through the web proxy, with web addresses and other data that may be used to identify the target site being encoded before the data is sent on to the web browser.

This has several advantages for the website visitor. It allows them to surf the web anonymously, with their right to privacy protected. It also prevents filtering software from limiting their access to blocked websites. While filtering software is often used to restrict access to unsavory sites, it also often blocks access to many useful sites, such as those used for research for school and work projects. Most filtering software does an imperfect job of properly classifying sites.

Some proponents of web filtering technology have actually changed their view on the subject after finding their own websites incorrectly classified and blocked by the technology they were formerly advocating the use of.