Polipo, a Caching Web Proxy Server

Polipo is a small caching web proxy server which was designed to be used as a personal cache or a cache shared among a small group of people to boost internet access. Polipo is commonly used as a web proxy for a small network or a single computer, is also used by larger groups. Polipo is released as a free software under the MIT license. The software is written in C and is compatible with different operating systems such as Windows, Linux, OS X, FreeBSD, OpenWrt, and OpenBSD.


To minimize latency, Polipo uses HTTP/1.1 pipelining when multiple HTTP requests are sent on a single TCP connection. Polipo has limitations to the file sizes of 2Gb or 4Gb on 32 bit systems so large requests can cause errors.  


Polipo was designed to perform a variety of functions such as to speeding up a web server by caching repeated request, assuring security by filtering traffic, and caching web and DNS lookups for several users that share the same network resources. Users can also configure Polipo to use and serve on-disk cached content when offline and perform content filtering.


Natively, Polipo is a software application with a command-line interface so users must type all commands on the keyboard and store all parameters in configuration text files. But users can also run the program non-interactively in an automated way, just like in a shell script. There are some independent GUI applications such as Dolipo, Solipo, and Polipoid that allow users to interact with Polipo using visual indicators and graphical icons and change its working parameters.


Polipo is compliant with HTTP 1.1 and it provides support for IPv4 and IPv6. It ensures privacy enhancement with traffic filtering. Due to the increasingly widespread use of encryption such as HTTPS which makes caching proxies obsolete, Polipo has not been maintained since November 2016.