HAProxy is a high-performance, open-source software load balancer and reverse proxy for TCP and HTTP-based applications. It's widely regarded as the world's most widely used software load balancer and is trusted by leading platforms to power their high-traffic services.
HAProxy serves as the open-source core that powers HAProxy One, a unified enterprise application delivery and security platform. While the open-source project provides the foundation, the HAProxy One platform expands on it with advanced security, centralized management, observability, automation, and enterprise support.
Why use HAProxy?
Technical teams choose HAProxy for its proven ability to improve application performance, reliability, and security in any environment. Its reputation is built on three core principles:
High performance and efficiency – Enabling greater scalability while reducing costs through lower resource use
Low latency – Ensuring a responsive user experience without sacrificing security
Observability – Ensuring logs and metrics are gathered at runtime, denoting what happened to a request and how long it took so that problems (and their sources) can be detected early and quickly.
Reliability and stability – Built upon 20+ years of continual development and support
Freedom – Bringing flexible deployment and configuration to your infrastructure to support a wide range of use cases
Secure architecture – Ensuring resilience against a wide variety of common vulnerabilities
Free and open source – Anyone can use HAProxy, and it's backed by a long history of community contributions.
Authoritative support – Expert support for enterprise customers, with detailed documentation and community resources for open-source users
What is HAProxy used for?
HAProxy is used to intelligently distribute traffic, making applications faster, more reliable, and more secure. Its solutions typically fall into four main categories:
These high-level solutions power many features native to HAProxy and HAProxy One, which we'll explain below.
What does HAProxy do?
HAProxy and HAProxy One support numerous functions related to application delivery. Anything you can do in HAProxy can be done in HAProxy One, yet HAProxy One comes with some unique functionality (which we've noted below). Organizations worldwide rely on HAProxy and HAProxy One for the following:
Load balancing – HAProxy and HAProxy One distribute requests among multiple backend servers using over 13 load-balancing algorithms — both static and dynamic — such as round-robin, least connections, and consistent hashing. We fully support TCP/HTTP(S) load balancing in HAProxy, and TCP/HTTP(S)/UDP/QUIC load balancing in HAProxy One.
API Gateway – HAProxy One helps APIs and services scale massively with high performance, security, and reliability features.
AI Gateway – HAProxy One helps cutting-edge AI/ML applications scale massively, while boosting reliability, strengthening security, and optimizing costs. Innovate freely and deliver improved user experiences with ease.
Multi-layered security – HAProxy One enables teams to implement DDoS protection and rate limiting, bot management, intelligent web application firewall (WAF) protection, AI gateway functionality, and more to protect applications from a broad spectrum of high impact threats — including zero-day vulnerabilities.
Deep observability – HAProxy Enterprise load balancer (the data plane) generates granular logs, 150+ runtime and security metrics, and other statistics to enable centralized monitoring and observability within HAProxy Fusion (the control plane). Create custom dashboards to view important information first, easily track anomalous client behavior, and view security layer responses at every step. Audit safely and securely via role-based access control (RBAC).
Centralized load balancer management – Centrally manage HAProxy Enterprise load balancers distributed across regions and business units with HAProxy Fusion. Oversee LB cluster groups, PKI, access policies, and more.
GUI and API – Simplify HAProxy with a powerful and intuitive GUI, enabling multi-cluster management, multi-cloud integration, and enterprise administration — all within a comprehensive observability suite.
High-performance SSL/TLS – Establish end-to-end traffic encryption, offload TLS encryption and decryption to HAProxy with TLS termination, set up mTLS authentication, and more — all with ultra-low latency and the ability to process over two million secure requests per second, per instance.
Health checks – HAProxy monitors the health of backend servers and removes failed instances automatically to maintain availability. Use global server load balancing (GSLB) enhanced with HTTPS health checks to securely connect to datacenters spread across numerous DNS zones (also available through the HAProxy ALOHA hardware or virtual appliance).
Kubernetes and cloud-native routing – Harness intelligent external load balancing, multi-cluster routing, direct-to-pod load balancing, and high-performance ingress for Kubernetes apps. Simplify integration with support for service discovery and the Kubernetes API. Secure your clusters with multi-layered security and comprehensive observability.
This isn't an exhaustive list of HAProxy One features. However, it does encompass some of the primary functions that deliver value to organizations across all industries and verticals.
How HAProxy works: platform and products
HAProxy is made of two related parts: the open-source core and the enterprise platform (HAProxy One).
HAProxy open source (the core)
The open source HAProxy project is the heart of HAProxy. This software is freely available and delivers high-performance load balancing, high availability, and SSL/TLS processing for TCP/HTTP(S) traffic. Its development is public and has been driven by our global community for over 25 years.
HAProxy’s other open source projects
HAProxy Technologies maintains a number of additional projects that help make application delivery and security easier for many use cases, including cloud-native:
HAProxy Data Plane API – A service that lets you configure the load balancer using RESTful HTTP commands, enabling dynamically-generated configurations
HAProxy Kubernetes Ingress Controller – Supercharge your Kubernetes environment by adding advanced TCP and HTTP routing that connects clients outside your Kubernetes cluster with containers running inside.
HAProxy Unified Gateway – A free, open-source solution for cloud-native application routing, featuring unified integration with the latest Kubernetes Gateway API and (coming next year) the existing Ingress API
HAProxy One (the enterprise platform)
HAProxy One is the world's fastest application delivery and security platform. Built for organizations of all sizes, it's a commercial product that combines the open-source core with advanced modules and products for security, management, observability, and global distribution.
HAProxy One comprises three main components that work together:
HAProxy Enterprise – A flexible data plane layer that provides high-performance load balancing, an API/Al gateway, Kubernetes application routing, best-in-class SSL/TLS processing, and multi-layered security.
HAProxy Fusion Control Plane – A scalable control plane that provides full-lifecycle management, monitoring, and automation of multi-cluster, multi-cloud, and multi-team HAProxy Enterprise deployments.
HAProxy Edge – A secure edge network that provides a high-capacity global ADN and threat intelligence — enhanced by machine learning — that powers the next-generation security layers in HAProxy Fusion and HAProxy Enterprise.
HAProxy's open source history
HAProxy's foundation in the open-source community is a critical part of its identity and reliability.
2000 (the project begins) – Willy Tarreau, a contributor to the Linux kernel, wrote the first source code for HAProxy. This open source software load balancer (sometimes called HAProxy Community) served as the foundation for all future development.
2001 – HAProxy 1.0 launches to help offload traffic from existing hardware load balancers.
2002 – HAProxy 1.1 launches with vital load balancing features, such as round-robin scheduling, simple health checks, and improved logging.
2009 – HAProxy 1.4 launches with client-side Keep-Alive support, HTTP authentication, and ACL-based persistence.
2010 – HAProxy 1.5 launches, adding critical features such as SSL support and compression, server-side Keep-Alive, and early DDoS protection.
2013 (HAProxy Enterprise is introduced) – HAProxy Technologies, the company, was formed and subsequently launched HAProxy Enterprise. Built directly upon our open-source core, HAProxy Enterprise added (and continues to add) enterprise-grade modules, features, and dedicated support to meet advanced use cases. Meanwhile, work continues to this day on HAProxy.
2016 – HAProxy Runtime API is introduced with the launch of HAProxy 1.7.
2018 – HAProxy 1.9 launches, delivering end-to-end HTTP/2 support and improving multi-thread scalability.
2019 – HAProxy 2.0 launches and introduces HAProxy Data Plane API, while adding cloud-native threading and logging. HAProxy Kubernetes Ingress Controller debuts, bolstering HAProxy Technologies' position as an essential platform for modern deployments.
2021 – HAProxy 2.4 launches, adding major enhancements such as HTTP/2 WebSockets and MQTT protocol support, dynamic SSL certificate storage, built-in OpenTracing, and DNS TCP resolution.
2022 – HAProxy 2.6 launches, adding support for HTTP/3 over QUIC, new HAProxy Runtime API commands (expanding its capabilities), and further performance optimizations.
2023 – HAProxy 2.8 launches with the Lua event framework, HTTP compression for requests, and new signing algorithms for SSL/TLS.
2024 – HAProxy 3.0 launches, adding virtual ACL and map file support (for rule-based traffic routing), persistent stats after reload, and sweeping performance enhancements.
2025 – HAProxy 3.2 launches, bringing automatic CPU binding (boosting performance for large scale, multi-core systems), experimental ACME protocol support, and QUIC efficiency improvements.
Since then, HAProxy has continually added new features and directly influenced the development of HAProxy One. To dig deeper into our release history and new features added along the way, check out our product release announcements. These encompass both development branches.
Today, HAProxy Technologies actively maintains both the open-source project and the HAProxy One enterprise platform. Willy continues to lead the core development team and acts as the company’s CTO. New features and enhancements often debut in the open-source version before being tested and migrated to the enterprise products.
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Frequently Asked Questions (FAQ)
Is HAProxy free?
Yes, the open-source HAProxy (Community Edition) is free. HAProxy One is a paid, commercial platform designed for organizations that require advanced security, scalability, centralized management, and enterprise support.
When should you use a commercial product versus an open-source one?
While the open-source HAProxy is robust enough for demanding workloads, we recommend HAProxy One for organizations that require advanced, enterprise-grade security (such as a customizable WAF or bot management), centralized management for multi-cloud deployments, and dedicated, authoritative support from the experts behind HAProxy.
How do you install HAProxy?
You can download HAProxy's source code from the community site or GitHub. HAProxy Enterprise installation instructions are provided in the official documentation for customers.
How do you configure HAProxy?
HAProxy is primarily configured via a text file. However, HAProxy users can configure their load balancers using the following mechanisms:
HAProxy Runtime API lets you configure some aspects of the load balancer on the fly at runtime, without reloading the service. It stores these changes in memory until the next reload or restart without writing them to your configuration file.
HAProxy Data Plane API lets you configure the load balancer using RESTful HTTP commands, enabling dynamically-generated configurations
HAProxy Fusion GUI and API enable consistent configuration across your HAProxy Enterprise clusters — letting you create new frontends, backends, and servers programmatically. Service discovery for Kubernetes and Consul also generates HAProxy configuration, unlocking automated traffic routing for dynamic backends.
You can learn more about configuring HAProxy by exploring our configuration tutorials.
Which HAProxy products include a built-in WAF?
Our next-generation HAProxy Enterprise Web Application Firewall (WAF) is included with HAProxy Enterprise, HAProxy Edge, and our HAProxy ALOHA appliance. HAProxy Enterprise WAF harnesses our Intelligent WAF Engine, powered by threat intelligence and enhanced by machine learning.
How do you upgrade HAProxy with zero downtime?
HAProxy supports "hitless reloads," which allow you to upgrade the software without dropping any active connections. This process involves gracefully shifting traffic between HAProxy nodes.
How can HAProxy help with a hybrid-cloud migration?
The HAProxy One platform simplifies hybrid-cloud migration by providing a unified and consistent way to manage, secure, and observe application traffic across both on-premises data centers and public cloud environments. HAProxy Fusion provides centralized management for these distributed deployments, and HAProxy Enterprise intelligently manages traffic as workloads shift between locations.