Apache HTTP Server vs Microsoft IIS vs Passenger: What are the differences?

## Introduction
When considering which web server software to use, it's important to understand the key differences between Apache HTTP Server, Microsoft IIS, and Passenger. Each of these web servers has its own sets of strengths and weaknesses that can impact the performance and functionality of your website.

1. **Operating Systems Support**: Apache HTTP Server is known for its cross-platform compatibility, supporting various operating systems such as Linux, Windows, and macOS. In contrast, Microsoft IIS is specifically designed to run on Windows operating systems, limiting its deployment options. Passenger, on the other hand, provides support for both Apache and Nginx web servers.

2. **Configuration and Management**: Apache HTTP Server offers a rich set of configuration options through its .htaccess files, providing flexibility and fine-tuning capabilities. Microsoft IIS, on the other hand, relies on the graphical user interface (GUI) for configuration, making it more user-friendly for beginners. Passenger simplifies the configuration process by automatically detecting and utilizing available resources, reducing the need for manual adjustments.

3. **Performance and Scalability**: Apache HTTP Server is renowned for its scalability and ability to handle a large number of concurrent connections efficiently. Microsoft IIS is known for its integration with other Microsoft products and services, streamlining the deployment of .NET applications. Passenger optimizes server performance by utilizing process isolation and smart load balancing techniques, enhancing scalability and responsiveness.

4. **Modules and Extensions**: Apache HTTP Server boasts a vast repository of modules and extensions, allowing users to extend the functionality and capabilities of the web server. Microsoft IIS offers a selection of modules tailored to the Windows environment, focusing on integration with Microsoft technologies. Passenger provides a curated list of modules that are optimized for performance and compatibility with Ruby, Python, Node.js, and other programming languages.

5. **Security Features**: Apache HTTP Server includes built-in security features such as SSL/TLS support, authentication mechanisms, and access control options to protect websites from security threats. Microsoft IIS offers robust security features like request filtering, IP address restrictions, and advanced encryption protocols to ensure data protection. Passenger enhances security by isolating application processes and implementing sandboxing techniques to mitigate vulnerabilities.

6. **Community Support and Updates**: Apache HTTP Server benefits from a large community of developers and users, providing comprehensive documentation, online forums, and frequent updates to address bugs and security issues. Microsoft IIS offers official support from Microsoft, ensuring timely updates, patches, and technical assistance. Passenger relies on a dedicated team of developers and contributors to maintain the project, offering continuous improvements and support for the user community.

In Summary, understanding the key differences between Apache HTTP Server, Microsoft IIS, and Passenger is crucial for choosing the right web server software that aligns with your website's requirements and infrastructure.