App Server vs Web Server: What’s the Difference?

The title of this post implies that there is a contrast between a web server and an application server. The reality is that in practical terms an application server and a web server are deployed simultaneously with the goal of fulfilling a purpose or addressing an user’s need when they visit a website.

There is not a unified standard that documents what the sole purpose of a web server is or what the sole purpose of an application server is. However, it is good to understand how these terms are commonly used and perceived.

Laptop to Cloud to Server Diagram

What Is a Web Server?

The job of a web server is to fulfill and accept a request that clients have for static content on a website. This includes things like videos, images, files, and HTML pages. The client is almost always making the request using a browser or mobile application. The request typically takes the form of Hypertext Transfer Protocol. This is also the case with the web server’s response.

What Is the Difference Between a Web Server and a Web Host?

Many people can’t tell the difference between web servers and web hosts, but essentially they’re not the same. A web server can be both a powerful computer and software. The software that runs that computer is called a web server and it is able to access any website.

On the other hand, a web host is a service that has access to a web server. People or companies that don’t have their own servers use web hosting services to store their websites on those servers for a monthly/yearly fee. Application servers also differ from regular servers.

Web servers can vary massively in performance and uptime. Shared uptime for hosting servers can vary depending on the performance metrics of the underlying server. Low quality infrastructure will lead to lower performance score. In a recent interview with Designer Daily Nathan Finch of Aussie Hosting, showed that over a 12 month observation of popular hosting solutions in Australia almost ⅓ of popular shared web hosts went down regularly.

Contrast this with performance data from dedicated hosts you see a common trend – cheaper infrastructure = worse performance.

Diagram of data surrounding the cloud

What Is an Application Server?

An application server will give clients access to something we refer to as “business logic.” This is used to create dynamic content. Dynamic content is called. It has the capability to transform data and then give the user a specialized function offered by a service, business, or application.

An application service client is typically the application itself. This might be a different application server or a web server. An application server and the client may communicate using HTTP, but it’s not a requirement in the same way that it is for web servers and their clients. There are several protocols that might be used, including different varieties of CGI.

Web Servers and Application Servers Working Together

When you visit a website and it has dynamic content and static content, the static content is usually being run by a web server and the dynamic content by an application server. Reverse proxy servers or load balancers are put in front of several web servers or application servers. When a request is sent, the traffic is routed to the appropriate server based on the content being asked for and based on a predefined load-balancing algorithm.

For example, we can imagine an online store that offers clients real-time pricing information and real-time information about the availability of products. When you visit the site, you will probably be presented with a form that will allow you to select the product or service that you want.

When your query is submitted, the site looks up the information. The results are returned, embedded in the HTML page. There are several ways that the site may go about carrying out this function. One option may be to use an application server, and another option may not use an application server. When you look at these scenarios, you get a clear picture of what an application server does.

A hallway at a Server farm

A Web Server That Does Not Use an Application Server

In this example, it’s just the web server that handles the online store’s functionality. The web server will receive your request and then send it to a server-side program that has the functionality to handle the request.

The server-side program checks pricing information from a flat file or database. Once it has the information, the server-side program uses that information when creating the HTML response. Then, the web server gives that information back to your browser.

So, essentially, it is the web server that is processing the HTTP request with an HTML page response.

A Web Server That Uses an Application Server

This example is like the first in one in that the web server will delegate its response generation to a script. Here, as we will see, there is a minor change because now business logic can be used for the pricing lookup with an application server. This means that the script does not know how to look up the data and create a response. What the script does is call the application server’s lookup service. Then, the script will be able to use the application server’s lookup services result and use that to generate an HTML response.

In this scenario, we see that the application server’s sole responsibility is to serve the business logic that wants the product price information. It’s not concerned with how to display the information or how the client is going to use the information. Instead, there is a back and forth of information between the client and the application server. The client makes a request and the application server’s lookup service gets the information and returns it to the client.

Here’s the benefit of using an application server. Since the pricing logic and the HTML response generating code are separate from each other, the pricing logic is flexible and can be used with multiple applications. There could be another client, such as a cash register, that can call the same service while an employee is checking out a customer. By contrast, in the first scenario, the pricing lookup service cannot be used by other clients because the information that it creates is embedded in the HTML page.

Why Is This Even a Question?

This is because as the design of application servers and web servers have progressed, the two types of servers have become intertwined and have overlapped. This is in response to the increased demand people put on websites. There are several applications that now act as both an application server and a web server.

There are several web application servers that communicate using HTTP protocol. And there are several web servers that take on the appearance of application servers because they have built-in functionality and built-in modules that allow them to natively support languages like PHP or proxy.

The bottom line is that in today’s world, most popular web servers and application servers are some form of hybrid. Most of the content-rich applications people use today rely on a mixture of static web content and application content that is dynamic. This content is delivered with a combination of application server and web server technologies.