HAProxy is a fast, reliable, open-source TCP/HTTP reverse proxy and load balancer used by some of the world’s largest websites. It distributes traffic across backend servers to provide high availability, fault tolerance, and smooth scaling, and is known for its exceptional performance under heavy concurrent load.

Key Features

• HTTP & TCP load balancing — routes Layer 4 (TCP) and Layer 7 (HTTP) traffic with round-robin, least-connections, and source-IP persistence
• High availability — health checks monitor backends and fail over automatically when a server goes down
• HTTPS / TLS termination — terminates SSL/TLS, offloading encryption from backend servers
• Sticky sessions — session affinity via cookies or source address for stateful applications
• Advanced ACLs and routing — redirect, rewrite, and route requests based on URL, headers, and connection properties
• Real-time statistics — a built-in stats page shows per-server health, throughput, and connection metrics
• Rate limiting & protection — connection limits, timeouts, and DDoS mitigation controls
• Logging & observability — detailed HTTP/TCP logs and Prometheus metrics export

Why Use HAProxy?

HAProxy consistently tops performance benchmarks for proxy throughput and connection handling. Its configuration is powerful and text-based, it uses very little memory per connection, and the active health-checking keeps your service online even when individual backends fail.

Use Cases

• Public-facing load balancer for web applications and APIs
• Reverse proxy in front of Nginx, Apache, or application servers
• TCP proxying for databases, mail, and other non-HTTP services
• High-availability front end with failover and consistent service discovery

Platform

Linux · macOS · BSD · Docker

Licence

GNU General Public License v2.0

Website

http://www.haproxy.org