squid is a high-performance proxy caching server for web clients, supporting FTP, gopher, ICAP, ICP, HTCP and HTTP data objects. Unlike traditional caching software, squid handles all requests in a single, non-blocking process.

squid keeps meta data and especially hot objects cached in RAM, caches DNS lookups, supports non-blocking DNS lookups, and implements negative caching of failed requests.

squid supports SSL, extensive access controls, and full request logging. By using the lightweight Internet Cache Protocols ICP, HTCP or CARP, squid caches can be arranged in a hierarchy or mesh for additional bandwidth savings.

squid is derived from the ARPA-funded Harvest Project http://harvest.cs.colorado.edu/