3-Tier Web Application Development

By Nannette Thacker

In web application development, three-tier architecture refers to separating the application process into three specific layers. What the user sees via a web browser is called the presentation tier and is content served from a web server. The middle tier performs the business logic processing that occurs, for example, when a user submits a form. The back end consists of the data tier which handles the database processing and access to the data. We'll take a simplistic look at each of these.

Presentation Tier

The Presentation Tier or User Interface is the portion the user sees when they open a web page in the browser. It is as simple as you reading this article all the way to searching a catalog and purchasing a product using a shopping cart. It is what is presented to the user on the client side within their web browser.

If you were to view the source code, you would only see code such as HTML, Javascript, and Cascading Style Sheets. On some sites, you may see Java Applets and Flash. Viewing source code on a web page, you would NOT see database queries or loops or calls to classes or any behind-the-scenes processing.

In ASP.net and utilizing Visual Studio or Visual Web Developer, developers can separate the user interface from the business logic and data access layer with various tools.

ASP.net allows using MasterPages to setup the site look and feel. As well, when creating a WebForm which utilizes the MasterPage, you may create it and allow the code to be placed in a separate file, known as codebehind, thus keeping your business logic in a separate layer from the look and feel.

You may also setup the site design using Themes, Skins, and Cascading Style Sheets.

Languages used in this layer are typically HTML, DHTML, CSS and javascript.

Business Logic or Application Tier

The Business Logic, Functional Process Logic, Business Rules (all pertaining to the same thing), are kept in a separate layer. In ASP.net, this is where you define your classes and source code. This can be in the App_Code folder for your classes and methods. Web languages typically used in ASP.net are VB and C#. You would not use HTML or Javascript in this layer. In this layer you typically define your classes, functions, sub procedures, properties, etc.

Data Access Tier

In ASP.net, the Data Access layer is where you define your typed datasets and tableadapters. It is where you define your queries or stored procedures. The business tier may then make use of this functionality. In your classes, rather than defining ad hoc queries, you may use a TableAdapter to access the Data Access Layer.

An Example

As an example of how this works, let's assume you are creating a web page that allows the user to enter information which you wish to then enter into a database. You first create a dataset and tableadapter that allows insert into the table, either by a query or stored procedure. This is your data access layer.

You then create a class, which retrieves the information from the form, checks for field validations and then uses the tableadapter to send the data to the database.

You create a web form, which can use a GridView control or other controls to allow the user to input the data into the web form. In the codebehind of the web form, you handle the submit button click event, and send the data from the form to your class, which sends the information to the database using the tableadapter.


When utilized properly, using a multi-tier architecture improves performance and scalability. If a web page needs an update or redesign, all of this may be handled by altering the CSS and HTML, without affecting the business or data logic. Any of the three tiers may be replaced or upgraded individually without affecting the other tiers. For instance, if you change the database on the back end, it wouldn't affect the presentation or business logic tiers, other than changing the database connection.

This is a simple introduction to the three-tier web architecture, but I hope it has helped you understand the layers of a multi-tier architecture.

May your dreams be in ASP.net!

Nannette Thacker


  • thanks for the info

  • Great article. Thank you for giving a birds eye view of the tier topology.


  • Short and clear! THX

  • Hi Nannette,
    Thanks very much, its brief and benefitable.

  • Thank you Nannette. You have explained 3-Tier Web Application Development clearly and I have found it to be very useful.

  • Its great. Thank you for very clear idea.

  • This article has really helped with a project I am doing. Thank you so much

  • Thank you for writing and posting this article. It cleared up some new terminology I've seen used in job descriptions as I'm searching for a new position.

  • Good article but let's get deeper.
    Tiers and Layers are often used interchangeably. However if you really want to propose a better architectural understanding note:
    - LAYER -> Logical Structure Solution (File System).
    - TIER -> Physical Structure Solution (Server).
    Therefore, Presentation, Business Logic and Data Access referred as TIER bring the understanding of having each operating from individual servers while LAYER accept many other architectural patterns structured within them such as MVC (Model-View-Controller), SOA (Service Oriented Architecture), EDA (Event Driven Architecture).
    In complicated scenarios and advanced solutions you could implement:
    Multitier Architecture (3-tier):
    - Server 1 -> Business Logic Tier:
    (hosting) - BLL (Business Logic Layer) = Event Handlers, Controllers, Webservices(REST, SOAP).
    - Server 2 -> Data Access Tier:
    (hosting) - DAL (Data Access Layer) = Models, Webservices (Data Interchange).
    - Server 3 -> Presentation Tier:
    (hosting) - UIL (User Interface Layer or Presentation Layer) = Presentation, Views, Webservices (Response).
    3 enterprise servers (TIERS) connected in the same Local network for response time performance plus 1 logic LAYER in each for load balance performance.
    My explanation samples is based on the difference between TIER and LAYER as infrastructure not the mentioned architectural patterns and all its layers composition.
    Hope this expands horizons.



  • its good but as an example ur missing the pratical part only theory is available over here

  • Hi

    Please write an small application with 3 tier approach with explanation

    this is request from me
    It will help new budding programmer


  • its so good
    its so easy to understand but only theory part is available

  • Thanks Thacker, your article is really very helpful.


  • nice tutorial but it could be better if u write an example with this ..

  • hi
    thakyou for explane the 3 tier ...

  • Thanks! It Helped me a lot

  • Hi Great post i'll be definitely come back to your site. keep this nice work  

  • for easy understanding of three tier architecture you can check this website also.....


  • it's very useful.


  • I want to create a new web application with 3 Tier. Please tell me how to start.

  • I really liked the article, and the very cool blog

  • This is good description in brief and i understand very well.i want to develop an application in 3 tier architect so please give me an article or any advice how it should be start


  • This topic is so interesting because I think it's easier and better than MVC model. My question is? How to organize all those files and folders?

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