Web servers use HTTP (Hypertext Transfer Protocol) and other protocols to respond to client requests made over the Internet.

The main job of a web server is to display website content by storing, processing, and delivering web pages to users. In addition to HTTP, web servers also support SMTP (Simple Mail Transfer Protocol) and FTP (File Transfer Protocol), which are used for email, file transfer, and storage.

Web server hardware is connected to the internet and allows data to be exchanged with other connected devices, while web server software controls how a user accesses hosted files. The web server process is an example of the client/server model. All computers that host websites must have web server software.

Web servers are used in web hosting, or the hosting of data for websites and web-based applications — or web applications.

How do web servers work?

Web server software is accessed through websites’ domain names and ensures the site’s content is delivered to the requesting user. The software side comprises several components, with at least an HTTP server. The HTTP server can understand HTTP and URLs. As hardware, a web server is a computer that stores web server software and other files related to a website, such as HTML documents, images, and JavaScript files.

When a web browser, like Google Chrome or Firefox, needs a file hosted on a web server, it requests it via HTTP. When the web server receives the request, it accepts it, finds the content, and sends it back to the browser via HTTP.

More specifically, when a browser requests a page from a web server, the process will follow a series of steps. First, a person will specify a URL in a web browser’s address bar. The web browser will then obtain the IP address of the domain name — either by translating the URL through DNS (Domain Name System) or by searching in its cache. This will bring the browser to a web server. The browser will then request the specific file from the web server by HTTP. The web server will respond, sending the browser the requested page again through HTTP. If the requested page does not exist or if something goes wrong, the web server will respond with an error message. The browser will then be able to display the webpage.

Multiple domains also can be hosted on one web server.

Examples of web server use

Web servers often come as part of a larger package of internet- and intranet-related programs that are used for:

Sending and receiving emails;
Downloading requests for File Transfer Protocol (FTP) files; and
Building and publishing web pages.

Many basic web servers will also support server-side scripting, which is used to employ scripts on a web server that can customize the response to the client. Server-side scripting runs on the server machine and typically has a broad feature set, which includes database access. The server-side scripting process will also use Active Server Pages (ASP), Hypertext Preprocessor (PHP), and other scripting languages. This process also allows HTML documents to be created dynamically.

Dynamic vs. static web servers

A web server can be used to serve either static or dynamic content. Static refers to the content being shown as is, while dynamic content can be updated and changed. A static web server will consist of a computer and HTTP software. It is considered static because the server will send hosted files to a browser as is.

Dynamic web browsers will consist of a web server and other software, such as an application server and database. It is considered dynamic because the application server can update any hosted files before sending them to a browser. The web server can generate content when the database requests it. Though this process is more flexible, it is also more complicated.

Standard and top web server software on the market

There are several standard web servers available, including:

Apache HTTP Server. Developed by Apache Software Foundation, it is a free and open-source web server for Windows, Mac OS X, Unix, Linux, Solaris, and other operating systems; it needs the Apache license.
Microsoft Internet Information Services (IIS). Developed by Microsoft for Microsoft platforms, it is not open source but widely used.
Nginx. It is a popular open-source web server for administrators because of its light resource utilization and scalability. It can handle many concurrent sessions due to its event-driven architecture. Nginx also can be used as a proxy server and load balancer.
Lighttpd is an accessible web server that comes with the FreeBSD operating system. It is fast and secure while consuming less CPU power.
Sun Java System Web Server is an accessible web server from Sun Microsystems that can run on Windows, Linux, and Unix. It is well-equipped to handle medium—to large-sized websites.

Leading web servers include Apache, Microsoft’s Internet Information Services (IIS), and Nginx — pronounced engine X. Other web servers include Novell’s NetWare server, Google Web Server (GWS), and IBM’s family of Domino servers.

Considerations in choosing a web server include how well it works with the operating system and other servers, its ability to handle server-side programming, security characteristics, and the publishing, search engine, and site-building tools that come with it. Web servers may also have different configurations and set default values. A high throughput and low latency web server will help create high performance.

Web server security practices

There are plenty of security practices individuals can set around web server use that can make for a safer experience. A few example security practices can include processes like:

A reverse proxy is designed to hide an internal server and act as an intermediary for traffic originating on an internal server;
Access restriction through processes such as limiting the web host’s access to infrastructure machines or using Secure Socket Shell (SSH);
Keeping web servers patched and up to date to help ensure the web server isn’t susceptible to vulnerabilities;
Network monitoring to make sure there isn’t any unauthorized activity and
Using a firewall and SSL, as firewalls can monitor HTTP traffic, and having a Secure Sockets Layer (SSL) can help keep data secure.