EXE1 file format contains executable program for Windows operating system and is no more than standard EXE file renamed for whatever purpose. It cannot be opened by standard mouse double-click, but has to be renamed with EXE extension in order to run the program.

EXE1 files are usually found in package installers when developer doesn’t want the program to be manually run by user. One such example is steam.exe1 file within Steam software installer or some game installers available on Steam platform. This extension type is also encountered in mail attachments or simple files downloaded from websites.