you may have requirement of opening a file but in case you don’t know it’s extensions, learn how to open files that have unknown extensions.
Before starting with that, let me tell you something about extensions. There are various extensions available in files. For example, executable files have extension .exe, MS word files have extension .doc/ .docx, pdf files have extension .pdf, web pages have extensions like .html/ .htm/ .php/ .aspx, etc. So in order to open a file you must know which file belongs to which category.
You can determine the extensions by right clicking the file and then selecting “properties”.
After clicking “Properties” you’ll get the details of the file.
So by doing this you can find the extension of the file. If you are still unable to find the extension then you can try “open with” by right clicking the file.
But sometimes a problem arises in which you won’t be able to find the extension of the file and the associated tool to open the file with. In that 
case what you can do is rather than going for internet to check which file extension is the file have. You can try the tools that are freely available to check for the extension.
Wolfram Alpha
Instead of looking on search engines, you can try the Wolfram Alpha website to find out the extension of file. The site will provide you all of the details of your file. Details like the proper extension, the file developer, the MIME, the file along with the file signature will be displayed here.
This will tell you all of the details of your file, but in case you are still unable to find the extension, then in that case you can try another software.
TrIDNET
There is an awesome concept known as the file signature. File signature can tell a lot about the file. It contains all the details like the file type, extension, etc. There are certain applications which can help you find the file signature. Once you found out about the file signature of your file, then you can easily get all of the other details. One of the most common and used application for this is TrlD File Identifier. So if you were unable to find the extension or the details about your file, then you can try this software to find all of the details.
So, once you download and install the software, open the file. Either you can browse the file or you can type the address of file by yourself. After that click on the “Analyze!” button. And if you want to know about the file signature, then click on the “Rescan Def’s” button.
These are the basic step by which you can find out the extension and other details of your files.
There are many other tools available for finding the extension/ details of the files. But I’ll recommend these tools only as they are easier to use.
So now you know about how to open files that have unknown extensions.
