Apache HTTP Server

Overview

Apache HTTP Server (Apache for short) is a free, open-source web server software maintained by the Apache Software Foundation. It is one of the most widely used web servers in the world, with a market share exceeding 30%. Originally developed by Robert McCool and first released in 1995, it supports Unix-like systems (such as Linux and FreeBSD), Windows, and macOS, and is available for both x86_64 and arm64 architectures. Apache is known for its modular architecture and supports dynamically loaded modules (such as mod_php and mod_ssl), providing features such as web hosting, reverse proxying, load balancing, and content caching. It is configured using httpd.conf and .htaccess, supports HTTP/1.1, HTTP/2, and HTTP/3 (experimental), and is suitable for static and dynamic websites, API services, and enterprise applications.

History and Development

• Origin:
  • 1995: Apache was developed based on NCSA httpd 1.3 by Robert McCool and the Apache Group with the goal of fixing NCSA httpd bugs and providing an open source alternative.
• Development History:
  • April 1995: Apache 0.6.2 was released, the first public release.
  • 1996: Apache 1.0 was released, becoming the most popular web server.
  • 1999: The Apache Software Foundation (ASF) was established to manage the Apache project.
  • 2004: Apache 2.0 was released, introducing the Multi-Processing Module (MPM) and IPv6 support.
  • 2013: Apache 2.4 was released, supporting HTTP/2 and the Event MPM.
  • July 2025: Apache 2.4.62 was released, fixing CVE vulnerabilities and optimizing performance and module compatibility.
• Community and Support:
  • Maintained by the Apache Software Foundation (ASF), it's hosted at httpd.apache.org, GitHub, and the forums (community.apache.org).
  • Supports English and multiple languages (Chinese is translated by the community), and is fully documented (httpd.apache.org/docs).
  • A Reddit user called Apache "a solid web server foundation."
• Open Source License:
  • Apache License 2.0, which permits commercial use and modification.

Key Features

Apache is built around modularity, high performance, and versatility, making it suitable for both web server and proxy scenarios. Here are its key features:

1. Multi-Processing Module (MPM)
   • Supports prefork (process mode), worker (thread mode), and event (event-driven mode), with the choice of which one to use depending on the workload.
2. Modular Architecture
   • Supports dynamically loaded modules, such as mod_php, mod_ssl, and mod_rewrite.
3. Virtual Hosting
   • Supports name-, IP-, or port-based virtual hosting.
4. SSL/TLS Support
   • Supports HTTPS and HTTP/2 via mod_ssl.
5. Load Balancing and Proxying
   • Supports reverse proxy (mod_proxy) and load balancing (mod_proxy_balancer).
6. .htaccess Support
   • Supports directory-level configuration (such as rewriting and authentication) using .htaccess files.
7. Performance and Hardware Support
   • Supports x86_64 and arm64, consuming 50-200MB of RAM.
8. Security and Privacy
   • Supports SSL/TLS, access control, and authentication modules.

Advantages and Limitations

Advantages

• Modularity:
  • Flexible expansion, suitable for custom configurations.
  • X's post claims, "Apache's module system allows for unlimited extensibility."
• Stable and reliable:
  • Widely used in production environments, with rich community resources.
• .htaccess support:
  • Convenient directory-level configuration, superior to Nginx's .htaccess-free architecture.
• Open source and free:
  • Apache License 2.0, supporting commercial use.
• Community support:
  • ASF and an active community provide documentation and modules.

Limitations

• Performance at high concurrency:
  • The process/thread model is inferior to Nginx's event-driven architecture.
• Complex configuration:
  • Steep learning curve, inferior to Caddy's simple configuration.
  • Solution: Use the Apache configuration generator.
• Comparison servers:
  • Nginx: High performance, event-driven architecture.
  • Lighttpd: Lightweight, suitable for embedded systems.
  • Caddy: Automatic HTTPS.

Summary

Apache HTTP Server is a free, open-source, high-performance web server that supports HTTP/2, HTTP/3, and WASM. It is centered around modularity, multi-processing modules, and virtual hosts. While Apache's modularity and .htaccess support are prominent, its high-concurrency performance is somewhat lacking.