What’s the Difference Between a Web Server and an Application Server?

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What's the difference between a web server and an application server?

Web servers and application servers are the technologies that allow the exchange of data and services over the internet. The client-server architecture is the underlying mechanism of the internet. When you visit a website or application, your browser (as the client) requests data from a remote server and displays the response. A web server is a software component that delivers static data like images, files, and text in response to client requests. An application server adds business logic to compute the web server's response. Both terms are used synonymously, and the most popular server software solutions today are hybrid web application servers.

How they work: web server vs. application server

Web servers and application servers have distinct independent processes. However, they’re invisible to the end user.

How a web server works

A web server is technology that hosts a website’s code and data. When you enter a URL in your browser, the URL is actually the address identifier of the web server.

Your browser and web server communicate as follows:

The browser uses the URL to find the server’s IP address
The browser sends an HTTP request for information
The web server communicates with a database server to find the relevant data
The web server returns static content such as HTML pages, images, videos, or files in an HTTP response to the browser
The browser then displays the information to you

A website that hosts static content like blogs, header images, or articles can run on a web server. However, most websites and web applications are much more interactive and require an application server.

How an application server works

An application server extends the capabilities of a web server by supporting dynamic content generation, application logic, and integration with various resources. It provides a runtime environment where you can run application code and interact with other software components, like messaging systems and databases. It uses business logic to transform data more meaningfully than a web server.

When you attempt to access interactive content on a website, the process works as follows:

The browser uses the URL to finds the server’s IP address
The browser sends an HTTP request for information
The web server transfers the request to the application server
The application server applies business logic and communicates with other servers and third-party systems to fulfill the request
The application server renders a new HTML page and returns it as a response to the web server
The web server returns the response to the browser
The browser displays the information to you

To use the example of an ecommerce website, when you add items to your cart, or check out items, you interact with the application server.

Key differences: web server vs. application server

Web and application servers have several key differences that set them apart.

Tasks covered

A web server hosts websites and delivers responses to simple requests. Web servers also log server activity and allow server-side scripting.

On the other hand, application servers have a more complex set of tasks. Application servers handle business logic to generate dynamic content by connecting with enterprise systems, services, and databases.

Protocols used

The primary protocol web servers use is the HTTP protocol. However, different web servers also support FTP and Simple Mail Transfer Protocol (SMTP). These two protocols facilitate file storage and transfer as well as email.

In addition to the protocols that web servers use, application servers use additional communication protocols to communicate with other software components. For example, they may use remote method invocation (RMI) and remote procedure call (RPC).

Content types

Web servers mostly deliver static content. Static content is content that a server doesn’t need to modify or process before delivering. For example, image files (like PNG, GIF, and JPEG), downloadable documents (PDFs), videos, and HTML files are all static content.

Application servers mostly deliver dynamic content. Dynamic content is content that changes based on how the user interacts with it. For example, dynamically generated reports, customized data representations, personalized UIs, database results, and processed HTML are all dynamic content.

Multithreading

Threads on a server are separate pathways of operation that enable the concurrent processing of tasks. In multithreading, the server creates and runs multiple threads simultaneously, and each handles a separate task or part of a task. Support for multithreading helps to deliver web content faster while managing more web traffic.

Most web servers don’t support multithreading. Web servers place each new connection request in a queue and use an event loop to monitor new entries and exits from the queue. To improve efficiency, the server processes requests by using non-blocking I/O and callbacks. Non-blocking operations and event-driven architecture allow web servers to handle concurrent connections.

Application servers use multithreading to provide high scalability and efficiency. If a request requires external resources, the application server uses separate threads to cover those interactions. It can process multiple threads at once, serving many client interactions in parallel.

How do application servers and web servers work together?

Application servers and web servers work together to handle client requests and deliver the correct content to the user. The web server always receives a new request first. If it can produce the information itself, it does so and sends back an HTTP response. It also checks that the data the user requested isn’t already in its cache.

If the web server can’t access the content the user requires, it forwards the request to the application server. The application server processes data and uses business logic to provide the correct information. It then passes the request back to the web server, which passes it on to the user. In certain architectures, you can also configure application servers to handle HTTP requests by themselves.

Summary of differences: web server vs. application server

	Web server	Application server
Tasks covered	Web servers deliver responses to simple requests.	An application server delivers more complex content from databases, services, and enterprise systems.
Protocols used	Web servers primarily use HTTP. They also support FTP and SMTP.	Application servers support many protocols.
Content types	Web servers deliver static content, like HTML pages, images, videos, and files.	Application servers deliver dynamic content, like real-time updates, personalized information, and customer support.
Multithreading	Does not typically use multithreading.	Uses multithreading to process requests concurrently.

How can AWS support your web server and application server requirements?

Amazon Web Services (AWS) offers several cloud web hosting solutions that provide a low-cost way to deliver web applications and websites. For more information, read about web hosting on AWS. Here are two AWS web hosting solutions:

Amazon Lightsail is the easiest way to launch and manage a web server using AWS. Lightsail includes everything you need to jump-start your website—a virtual machine, SSD-based storage, data transfer, DNS management, and a static IP—for a low, predictable price.
Amazon Elastic Compute Cloud (Amazon EC2) provides resizable compute capacity for application servers in the cloud. It’s designed to make web-scale cloud computing easier for developers. It also allows maximum scalability and availability for websites and web applications. Amazon EC2 changes the economics of computing, and you pay only for capacity that you actually use.

Alternatively, AWS offers technologies that you can use to run code, manage data, and integrate applications without managing servers. AWS serverless solutions provide high availability, pay-for-use billing and automatic scaling for your business. For more information, go to Serverless on AWS.

Here are ways you can use AWS serverless services: