First check that the file actually has no extension:
– Right-click on the file, select ‘Properties,’ and look at the ‘type of file’ in the ‘General’ tab of file properties. If it just says ‘File’ it has no extension, OR…
– Check the file extension from the ‘Type’ column in Windows file explorer, OR…
– Select the ‘View’ tab from the top ribbon and check the box beside ‘File name extension’.
If the file has an extension but you can’t open it, this is likely to be because you don’t have the relevant program on your computer/device. Ways to open it include:
– Visit fileinfo.com (https://fileinfo.com/), enter your file’s extension in the search bar, and install one of the suggested programs.
– Visit toolsley.com (https://www.toolsley.com/file.html) and drag and drop the file to identify it.
– Download the UK government’s DROID tool (https://github.com/digital-preservation/droid/) and use that to identify the file extension listed in the ‘Format’ column.
– Use a hex editor, such as Free Hex Editor Neo (https://www.hhdsoftware.com/free-hex-editor).
– After launching the editor, open the file, scroll to the right end of the block of numbers, and you will see the file extension.