.MASTER File Extension
What is a MASTER file?
A MASTER file is a master webpage or template created with ASP.NET. It is used for building multiple pages with the same layout. Each MASTER file typically includes defined header, navigation, and footer sections as well as editable areas. MASTER files are constructed using HTML, just like a typical webpage.
When editing a webpage based on a master page, the non-editable areas are shaded gray while alterable items are clearly shown. Editable areas can be defined by editing the master page directly. Master pages work in conjunction with content pages, which merge with the master page to produce the output seen by the user.
How to open a MASTER file
You can open a MASTER file in Microsoft Visual Studio (Windows). To do so, open a Visual Studio project and select Project → Add Existing Item. Then, navigate to and open your MASTER file. This will add the MASTER file to your Visual Studio project.