Options dialog box: Projects and Solutions > Build and Run
Applies to: 
Visual Studio 
Visual Studio for Mac
Note
This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here
In this dialog box, you can specify the maximum number of C++ or C# projects that can build at the same time, certain default build behaviors, and some build log settings. To access these options, select Tools > Options expand Projects and Solutions, and then select Build and Run.
Maximum number of parallel project builds
Specifies the maximum number of C++ and C# projects that can build at the same time. To optimize the build process, the maximum number of parallel project builds is automatically set to the number of CPUs of your computer. The maximum is 32.
Only build startup projects and dependencies on Run
Builds only the startup project and its dependencies when you use the F5 key, the Debug > Start Debugging menu command, or applicable commands on the Build menu. If unchecked, all projects and dependencies are built.
On Run, when projects are out of date
Applies to C++ projects only.
When running a project with F5 or the Debug > Start Debugging command, the default setting Prompt to build displays a message if a project configuration is out of date. Select Always build to build the project every time it is run. Select Never build to suppress all automatic builds when a project is run.
On Run, when build or deployment errors occur
Applies to C++ projects only.
When running a project with F5 or the Debug > Start Debugging command, the default setting Prompt to launch displays a message if a project should be run even if the build failed. Select Launch old version to automatically launch the last good build, which could result in mismatches between the running code and the source code. Select Do not launch to suppress the message.
For new solutions use the currently selected project as the startup project
When this option is set, new solutions use the currently selected project as the startup project.
MSBuild project build output verbosity
Determines how much information from the build process is displayed in the Output window.
MSBuild project build log file verbosity
Applies to C++ projects only.
Determines how much information is written to the build log file, which is located at \<ProjectName>\Debug\<ProjectName>.log.