What Is a Web Server?

A web server is software — running on a physical or virtual machine — that stores a website's files and delivers them to browsers over the internet. When you type a URL or click a link, your browser sends an HTTP request to a web server, which locates the requested resource and returns it as an HTTP response. The term "web server" is used for both the software (such as Nginx or Apache) and the machine it runs on.

How a Web Server Works

The exchange follows the request-response model of HTTP. Your browser opens a connection to the server (today almost always secured with TLS, which makes it HTTPS) and sends a request line such as GET /index.html together with headers describing the browser and what it can accept. The server parses the request, finds or generates the resource, and returns a status code — 200 for success, 404 if the resource is missing, 301 for a redirect, 500 for a server error — followed by the response body and its own headers.

A single server handles many connections at once and usually responds in milliseconds. Caching, persistent connections (keep-alive), and compression all cut the work done and the bytes sent per request.

Static vs. Dynamic Content

For static content — HTML files, images, CSS, and JavaScript — the server simply reads the file from disk and sends it back. For dynamic content, the server hands the request to application code (PHP, Node.js, Python, and so on) that builds a response on the fly, often after querying a database. Many deployments place a fast web server like Nginx in front as a reverse proxy: it serves static files directly and forwards dynamic requests to the application server behind it.

Popular Web Servers

• Nginx uses an event-driven architecture known for high concurrency and low memory use, and is widely used as a reverse proxy and load balancer as well as a web server.
• Apache HTTP Server is one of the oldest and most flexible servers, with a large module ecosystem and per-directory configuration through .htaccess.
• Caddy is a newer server that provisions and renews HTTPS certificates automatically out of the box.
• Microsoft IIS is the web server built into Windows Server, common in .NET environments.

Web Server vs. Application Server

The two terms overlap but are not identical. A web server's core job is to speak HTTP and serve content; an application server runs your business logic and is often specialized for a language or framework. In practice a web server frequently sits in front of one or more application servers — terminating TLS, serving static assets, and routing everything else — a separation that improves both performance and security.

What to Configure in Production

Running a web server in production means setting a few things deliberately: which ports to listen on (80 for HTTP, 443 for HTTPS), a valid TLS certificate so traffic is encrypted, virtual hosts so one server can serve several domains, sensible timeouts and request-size limits, and access and error logging so you can diagnose problems. Keeping the server patched matters too, because it is directly exposed to the internet.

A web server rarely works alone — see how a proxy server and a load balancer sit in front of it, and why HTTPS is the default today.

Frequently Asked Questions