What is master page in ASP.NET?

A master page in ASP.NET serves as a template that defines the common structure, layout, and behavior for a set of related web pages. It contains placeholders for content, which can be overridden by individual content pages, allowing them to provide unique content while inheriting the overall look and functionality defined by the master page. This approach improves the maintainability of a website by avoiding redundant code duplication for shared site structure or behavior.

Master pages

By using a single master page, you can establish a consistent look and feel, as well as standard behavior, across multiple pages or a group of pages within your application. Creating a master page is similar to creating a regular page, but it is saved with the .master file extension instead. End users are completely unaware of the presence of master pages, as they only interact with the resulting combined output of the master page and the content page.

Master pages provide developers with the flexibility to create web applications where pages share a common layout, reducing the effort required to manage the overall design and structure. The layout of master pages is easy to create, maintain, and assign to a web application. To designate a master page, you use a special @ Master directive, which replaces the @ Page directive typically used in ordinary .aspx pages.

< %@ Master Language="C#" % >

Whenever a master page's layout or formatting is changed, all of its content pages output is likewise immediately updated, which makes applying site-wide appearance changes as easy as updating and deploying a single file .


By using master pages, you can streamline the development process, enforce a consistent visual identity, and simplify the management of shared elements across your ASP.NET application.