Web servers and application servers work together to serve dynamic web application content over the Internet. Dynamic web application content includes automatically populated fields, such as recommended items after an e-commerce purchase, and user-edited content, like an online banking form. Most web applications must have dynamic content to function. This requires web and application servers to work together.
Jump to:
- Web servers
- Application servers
- How web servers and application servers work together
- Differences between web servers and application servers
- Popular web servers
- Popular application servers
Web servers
Web servers run as one computer, multiple computers, or a rack. They can be as simple as a laptop on a desk or as high-performance as rack servers in an enterprise data center. On their own, web servers use the HTTP or HTTPS protocol to deliver static web content to web pages on end users’ devices. Static content is cached and remains the same each time it is loaded unless the source code is manually edited. The web browser uses HTML and CSS to place static content on the page as the designer or developer designated.
Web servers may use add-ons to support scripting languages like PHP or Python to provide dynamic content to web pages. These scripting languages provide functionality for connecting to databases or making calls to third-party APIs, which are needed for web application content.
Application servers
Application servers typically sit behind web servers, offering dynamic content (like account logins and cloud-based office suites) upon request. They use scripting languages, like those mentioned above, to create dynamic web page content. Those scripts can request data from databases or third parties and then return content to the web server, which formulates an HTML response for the end user.
Application servers interface with multiple protocols: HTTP and HTTPS, but also Transport Layer Security (TLS). This is the most recent secure standard of confirming the authenticity of a web certificate, surpassing SSL.
Application servers use multithreading—the ability to communicate with multiple clients and serve multiple requests simultaneously—to more efficiently answer requests.
How web servers and application servers work together
Application servers and web servers communicate using operating system threads that process web server requests and provide a response. Application servers provide dynamic web content to web pages via the web server. They transform database-stored data and process complicated requests.
When an Internet user types the domain name of a web application into their browser:
- The web client sends the user’s request to the web server via an HTTP request.
- The web server requests dynamic content from the application server, via a programming language like PHP or Python.
- The application server requests data from a database on the server and returns it to the web server with any requested dynamic content.
- The web server returns the results of the end user’s request to their browser.
Reverse proxy servers and load balancers handle web traffic requests, passing them to the servers that have the bandwidth to best manage end user demands.
Differences between application servers and web servers
Application servers and web servers work together and have some similar functions. Web servers only serve HTTP and HTTPS requests, and they serve strictly static content without using additional scripting languages. Application servers provide dynamic web content.
Most web applications require both web servers and application servers to collaborate and deliver dynamic web content. Frequently used, highly trafficked web applications require at least one web server and one application server.
Popular web servers
Apache is a free, open-source web server that’s highly customizable for developers. With scripting languages added to its services, Apache can deliver both types of web content.
Nginx is also free and open-source. Aside from being a web server, it works as a load balancer, reverse proxy, and API gateway. Around 2019-2020, it surpassed Apache as the most-used web server in multiple market data sources.
Popular application servers
Oracle WebLogic is a Java Enterprise Edition application server. It’s useful for infrastructures with containers because it can run on Kubernetes, a container orchestration platform. WebLogic can run both on an enterprise’s premises and on Oracle Cloud Infrastructure (OCI).
Apache Tomcat, technically a web server, does not have all application server capabilities, but it is termed one by the server industry. It supports Java, including servlets, and is able to serve content to applications that only need Java functionality.
IBM WebSphere functions both as a web application server and an application building tool. It has a Java EE runtime environment for enterprise application delivery.
