HAProxy

HAProxy earned its reputation as the load balancer that sits in front of some of the busiest sites on the internet without becoming the bottleneck. It works at both Layer 4, balancing raw TCP, and Layer 7, where it can inspect and route HTTP, so one proxy covers everything from database connections to web requests.

The feature set is built for production traffic under pressure: HTTP/2 and HTTPS, IPv6, FastCGI, the PROXY protocol, content caching, and DDoS mitigation, all aimed at high availability and even distribution across backend pools. TLS 1.3 termination rounds out the front-door duties.

Written in C and developed by HAProxy Technologies, it ships as source you build per the INSTALL file, with prebuilt packages listed on the project wiki. Self-host on Linux. Licensed GPL-2.0-or-later with LGPL-2.1 headers.