What is Squid Caching Proxy, and How Do You Use It?

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cartoon of squid

Squid is a caching and forwarding software usable as an HTTP web proxy. Created for the Linux platform as a part of the Harvest project at the University of Colorado Boulder, it’s a free software licensed under the GNU General Public License. Squid version 1.0.0 was released in July 1996. Its current stable release dates from December 2021. At present, almost all Squid developers work as volunteers.

What it does

Squid runs on most available operating systems including Windows. Here are ways to use it:

  • Combined with company firewalls to support security functions.
  • Configured for content caching and as a reverse proxy.
  • Functioning as a forwarding proxy, with identifying headers stripped out of a request.

Squid basics

With the Squid proxy server software in place, you can configure one or more web browsers to use it as a HTTP proxy server. Squid then stores copies of data returned from your requests. This cache fulfills subsequent requests for the same data, reducing response time and bandwidth use.

On the Internet, this basic proxy function by itself does necessarily hide your identity. However, with other Squid features, you can make your connections anonymous. For example, you can configure the software to disable selected header fields in the request. Or you can modify their content and let them go through.

Reverse proxy

With the basic setup described above, which you can modify as needed, Squid operates as a normal proxy. However, a reverse proxy setup is also available. And you can use both setups on a single Squid proxy, letting you use it as both types of servers.

Like the basic setup, the reverse proxy supplies requests from a cache. One main difference is that the basic setup caches data from an unlimited number of webservers, but for a limited number of clients (users). This basic setup works well for a cache from a single Internet source shared by a company’s employees. In contrast, the cache in a reverse Squid proxy supplies data from a limited number of webservers (sometimes just one) to an unlimited number of clients. This setup works well for a business hosting its own website on a web server owned by an ISP. So then the Squid server acts as a reverse proxy between the business and its outside customers.

Availability

Getting Squid

There are several ways you can obtain Squid proxy for use:

Installing and Configuring

Here is a link to a simple process for installing and configuring Squid on Windows. First, check out How to Install Squid 3.5 on Windows.

For setup and configuration on Ubuntu for Linux, see How to Setup Your Own Free Proxy Server Using Squid Proxy.

Wrapping up

With advanced features and configuration, Squid can build “content clusters” that let you route and load-balance requests over several webservers.  As a caching tool, Squid speeds delivery on data requests and saves bandwidth. For proxy users, it helps ensure privacy, security, and anonymity – all essential in today’s environment.

Core Topic: What Are Datacenter Proxies and How Do They Work?

Published by Thomas Rankin