Automatic scaling

Automatic scaling lets a form and its controls, designed on one machine with a certain display resolution or font, display appropriately on another machine with a different display resolution or font. Forms and controls intelligently resize to stay consistent with native windows and other applications on both users' and other developers' machines. Automatic scaling and visual styles help Windows Forms applications maintain a consistent look when compared to native Windows applications on each user's machine.

For the most part, automatic scaling works as expected in Windows Forms. However, font scheme changes can be problematic. For an example of how to resolve this issue, see How to: Respond to Font Scheme Changes in a Windows Forms Application.

DPI awareness in .NET

DPI awareness is configured through the project file using the ApplicationHighDpiMode property, which is set to SystemAware by default. This configuration works with the application bootstrap system to automatically configure DPI handling when your application starts.

The default and recommended DPI mode for Windows Forms applications is SystemAware. This mode queries for the DPI setting once at application startup and uses that value throughout the application's lifetime, providing consistent scaling behavior.

Configure DPI mode in your project file:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <ApplicationHighDpiMode>SystemAware</ApplicationHighDpiMode>
  </PropertyGroup>
</Project>

Note

While the recommended approach is to configure DPI through the project file, you can still use an application manifest file (app.manifest) to override these settings. However, using the manifest is discouraged because it can cause conflicts with the application configuration. For more information, see Compiler Warning WFO0003.

Visual Studio designer considerations

When designing forms in Visual Studio, you might need to configure the designer's DPI awareness separately from your application. Starting with Visual Studio 2022 version 17.8, you can set the ForceDesignerDPIUnaware property in your project file to make the Windows Forms designer run in DPI-unaware mode. This setting helps avoid rendering issues when designing forms on high-DPI monitors:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <ForceDesignerDPIUnaware>true</ForceDesignerDPIUnaware>
  </PropertyGroup>
</Project>

This property only affects the Visual Studio designer and doesn't change how your application runs. For more information, see Disable DPI-awareness to address scaling issues.

Available DPI modes include:

SystemAware—The application queries for the DPI once at startup and uses this value for the lifetime of the app.
PerMonitor—The application checks for DPI changes on a per-monitor basis and rescales when DPI changes.
PerMonitorV2—Similar to PerMonitor, but enables child window DPI change notifications and improved scaling behavior.
DpiUnaware—The application doesn't scale for DPI changes, and Windows handles the scaling.
DpiUnawareGdiScaled—Similar to DpiUnaware but provides better quality for GDI-based content.

For more information about configuring DPI settings, see What's new in Windows Forms for .NET 6.

Need for automatic scaling

Without automatic scaling, an application designed for one display resolution or font appears too small or too large when that resolution or font changes. For example, if you design an application using Tahoma 9 point as a baseline, without adjustment it appears too small when run on a machine where the system font is Tahoma 12 point. Text elements, such as titles, menus, and text box contents, render smaller than other applications. Furthermore, the size of user interface (UI) elements that contain text, such as the title bar, menus, and many controls, depend on the font used. In this example, these elements also appear relatively smaller.

An analogous situation occurs when you design an application for a certain display resolution. The most common display resolution is 96 dots per inch (DPI), which equals 100% display scaling, but higher resolution displays supporting 125%, 150%, 200% (which respectively equal 120, 144, and 192 DPI) and above are becoming more common. Without adjustment, an application, especially a graphics-based one, designed for one resolution appears either too large or too small when run at another resolution.

Automatic scaling addresses these problems by automatically resizing the form and its child controls according to the relative font size or display resolution. The Windows operating system supports automatic scaling of dialog boxes using a relative unit of measurement called dialog units. A dialog unit is based on the system font, and its relationship to pixels can be determined through the Win32 SDK function GetDialogBaseUnits. When a user changes the theme used by Windows, all dialog boxes automatically adjust accordingly. Windows Forms supports automatic scaling either according to the default system font or the display resolution. Optionally, you can disable automatic scaling in an application.

Caution

Arbitrary mixtures of DPI and font scaling modes aren't supported. Although you can scale a user control using one mode (for example, DPI) and place it on a form using another mode (Font) with no issues, mixing a base form in one mode and a derived form in another can lead to unexpected results.