Squid Proxy
Squid is a mature, open-source caching and forwarding proxy server that supports HTTP, HTTPS, and FTP, commonly used to reduce bandwidth usage and control outbound web access.
Definition
Squid is a mature, open-source caching and forwarding proxy server that supports HTTP, HTTPS, and FTP, commonly used to reduce bandwidth usage and control outbound web access.
Overview
Squid primarily operates as a forward proxy, sitting between client devices and the wider internet, unlike reverse proxies such as Nginx or Varnish Cache that sit in front of backend servers. It caches frequently requested web content so repeat requests can be served locally, reducing external bandwidth consumption and improving response times for users on the same network. Beyond caching, Squid is widely used for access control: organizations deploy it to enforce network policies such as blocking specific sites, restricting bandwidth per user or group, requiring authentication before internet access, and logging outbound traffic for auditing or compliance. It supports flexible ACL (access control list) rules that can match on source IP, destination, time of day, URL patterns, and more. Squid has been actively developed since the mid-1990s and remains a common building block in enterprise network infrastructure, ISPs, and educational institutions, often deployed alongside firewalls to add content filtering and caching to outbound internet traffic. It is often mentioned alongside HAProxy in this space.
Key Features
- Forward proxy caching of HTTP, HTTPS, and FTP content
- Flexible ACL rules for controlling and filtering outbound internet access
- Bandwidth reduction through local caching of frequently requested content
- Authentication support for gating internet access by user or group
- Detailed access logging for auditing and compliance
- Support for transparent proxying and SSL bumping for HTTPS inspection