About the file extension shtml. Our goal is to help you understand what a file with a *.shtml suffix is and how to open it. The Server Side Include HTML file type .An shtml file extension is related to the HTML server side include files used by SSI Server Side Includes ..The SHTML file type is primarily associated with ‘HTML File Containing Server Side Directives’ by Microsoft Corporation..Read How To Open File Extension SHTML. Technical Details and Useful Information About File Extension SHTML. Fix File Extension Errors..