MSVC build errors > C1083

C1083: cannot open include file

fatal error C1083: Cannot open include file: 'json.hpp': No such file or directory

The compiler did not find the header named by an #include in any directory it searched.

Causes and fixes

1. Its folder is not an include directory. Add it to C/C++ > General > Additional Include Directories, relative to the project with $(ProjectDir) or $(SolutionDir) rather than as an absolute path.
2. It is set for another configuration or platform. Settings made for Debug or Win32 only do not apply to Release or x64: select All Configurations and All Platforms when you add the directory.
3. Quotes and angle brackets search differently. #include "file.h" looks first next to the including file; <file.h> only in the include directories.
4. The path in the directive is wrong. Check the folder names in #include "lib/file.h" against the directory you added.
5. A dependency or an SDK is not installed. For Windows or standard headers, install the Windows SDK or the C++ workload in the Visual Studio Installer; for a library, restore it, for example with vcpkg.

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Related errors: C2065, LNK1104, MSB8036. See all guides.