This question is much asked and much answered, but I can’t find a single answer that really seems to get to the nub of the problem and which really answers the question as asked. Which is to say, if I simply Create New Project -> Console App -> (choose a name for the project) -> Create then the project is in 32-bit mode. It’s trivial to click where it says X86 in the tool bar and change it to X64. Problem solved. You don’t even have to go into Configuration Manager or any similar complicated strategies that many answers through the years have suggested. But still, I have to change the X86 to X64 every single time I make a new project. And in addition, the very process of defaulting to X86 has created a gazillion little files and folders for the X86 version of the project that really aren’t needed. So the question is not how to make a 64-bit app. That’s extremely easy. And the question is not about how to convert a 32-bit app into a 64-bit app. That’s also extremely easy. The question is how to configure Visual Studio 2019 Community Edition so that a new project defaults to 64-bit in the first place.
By the way, all the answers on the Microsoft forums start out with "Open the C++ project that you want to configure." But there is no existing project if what you are trying to do is to set the default for new projects. Also, I did find default.vcxproj and played with it a bit. I didn’t see anything there that established a default of X86 vs. X64. But I did see that the X86 entries were in front of the X64 entries. I moved the X64 entries in front of the X86 entries, but that did not change the default. It did change the order of the way entries were displayed when I clicked the X86 vs. X64 box in the tool bar. Another promising file was shared.vcxproj. It appears that it may hold the default, but there I haven’t yet found any forum messages suggesting that it should be changed to solve this problem.
Source: Windows Questions C++