What is a web server?

A web server is a software used for serving files to websites on the Internet. The web server software is responsible for ensuring the communication between the server and the client is secure and flawless. The software works as a link between two machines (a physical server and a user’s device). When a user makes a request, the web server grabs the files from the physical server and delivers them to the user. So, web servers must serve different pages to different users at the same time.

Most popular web servers

According to the W3Techs’ statistics, the top 3 web servers — as of April, 2021 — are Apache, Nginx and Cloudflare Server. According to Netcraft’s statistics, the 3 most used web servers — as of March 2021 — are Nginx, Apache and OpenResty. 

Apache HTTP Server

The Apache web server, officially known as Apache HTTP Server, was released in 1995. Apache is a free, open-source web server; developed and maintained by the Apache Software Foundation (ASF). It is one of the most popular web servers around the world. As of April, 2021, Apache holds 34.1% of the market, according to W3Techs and 25.98% according to Netcraft.

Apache is highly flexible and customizable; functionalities can be easily turned on and off. It offers a lot of modules for security, authentication, caching, URL rewriting, etc. Besides, it allows custom server configurations using the .htaccess file. It also supports many applications: CMS, ERP, web frameworks, programming languages… Apache HTTP Server is a stable solution and one of the most reliable web servers.

Some of Apache’s main features

• Free and open-source
• Module-based architecture
• Easy configuration and customization
• Regular updates and security patches
• Big community of developers
• Compatibility with IPv6

The Apache HTTP Server Project aims to develop and maintain a commercial-grade, open-source server for modern operating systems. It also aims to provide a secure, efficient and extensible web server which provides HTTP services while meeting the current HTTP standards. The Apache HTTP Server project is part of the Apache Software Foundation, the world’s largest open-source foundation.

Nginx

Nginx is an open-source, high-performance web server, released in 2004. It has become one of the most used web servers, together with Apache. Nginx is an ideal solution for managing high-traffic websites. Many high-visibility websites and applications, such as Netflix or Pinterest, use the Nginx web server. As of April, 2021, Nginx holds 33.7% of the market, according to W3Techs and 35.34% according to Netcraft.

Its great success lies significantly on its ability to tackle the c10k problem — which stops some web servers from managing more than 10,000 simultaneous connections. It has two different versions: OSS Nginx and Nginx Plus. Nginx is often used as a software load balancer and works smoothly with PHP-FPM.

Some of Nginx’s main features

• Free and open-source
• Asynchronous, event-driven architecture
• High-performance
• Low memory consumption
• Compatibility with IPv6

LiteSpeed

LiteSpeed is a paid, proprietary web server developed by LiteSpeed Technologies; released in 2003. It has three licenses available: Free Starter, Site Owner and Web Host. It is a paid alternative for high-traffic websites, offering high-performance and great scalability. As of April, 2021, LiteSpeed holds 8.3% of the market, according to W3Techs and 3% according to Netcraft.

The LiteSpeed web server is optimized to securely handle thousands of concurrent customers, without consuming many memory and CPU resources. It is compatible with many popular control panels — such as Plesk and DirectAdmin — and with many features which are commonly used in Apache, for instance, mod_security, mod_rewrite and .htaccess configuration.

Some of LiteSpeed’s main features

• Event-driven architecture
• Lightweight
• Easy configuration
• Built-in anti-DDoS features
• Zero-downtime maintenance

Microsoft-IIS

Microsoft-IIS or Microsoft Internet Information Services is a web server released by Microsoft in 1995. It was developed to be used with Windows NT. Its modular architecture allows adding and removing extensions/modules easily. It also includes multiple built-in security features and authentication mechanisms. Microsoft-IIS is often used to host ASP.NET web applications and static sites. As of April, 2021, Microsoft-IIS holds 7% of the market, according to W3Techs and 5.96% according to Netcraft.

Some of Microsoft-IIS’ main features

• Module-based architecture
• Security and control
• Remote management

OpenResty

OpenResty is a web server, with an event-driven architecture, based on Nginx and LuaJIT. It is able to handle thousands of connections at the same time, as it is designed for building scalable, high-performance web applications and services. As of March, 2021, OpenResty holds 6.55% of the market, according to Netcraft.

Some of OpenResty’s main features

• Event-driven architecture
• High performance

This list includes some of the most used web servers, but there are many other alternatives available. The perfect choice will depend on the project requirements and goals, since a static website for a small business won’t demand the same features as a high-traffic site built on WordPress.