For newer Windows 10 versions, you can use Microsoft Photos app to open JPG files. For older Windows 10 versions, you can use Windows Photo Viewer to open JPEG/JPG file. If you are unable to open JPG file with Windows 10 built-in photo viewer software, you can try to use other image viewers for Windows 10 like Paint, Paint 3D, Photoshop, etc. to open and view JPG files.