Knowledge Base

File extension description in German
File extension description in French

File Extension UNKNOWN

Every file typically has an extension, but occasionally you can come across the files in the unknown format. In this case the challenge is to try and identify the file type and then find an application which will open it. The good news is that it is possible to identify a format even if the file contains an .UNKNOWN file extension or no extension at all.

In terms of content you will be unable to tell what data is contained within an UNKNOWN file extension unless you figure out what program created the file. In this regard, the type of operating system you use may not be of much assistance. For example, if you use Windows and you click on the UNKNOWN file, it will only provide you with recommendations as to what program allows you to open and use it. You can choose a program from the suggested list but more often than not, none of them are programs that will open the file.

How to Open UNKNOWN Files

If you have an UNKNOWN file type, the format can still be identified using the file signature. The signature data is stored inside the file and is contained in any file that is created regardless if it has an extension or not. There are also programs which are capable of reading the signature data to determine the format when the extension is unknown or missing.

One of the most widely used programs is known as TrIDNet which is designed to identify UNKNOWN file types. You simply download and install the program and then unzip the TrIDNet utility. Next you double-click on the TRIDnet.exe file and then choose Rescan Defs to insert the signature data. Once the signatures are finished loading, you simply drag and drop the UNKNOWN files that you want to open and use.

The program will display different formats which match the signature data. Then you can determine which program will allow you to open and use them. Once you have identified the files, it is necessary to rename them and follow the name with a dot and the appropriate extension. This makes the file usable and able to be accessed with the corresponding program.

Another resource which is effective for opening UNKNOWN files regardless of the operating system you use is This is a website with access to a database of free programs which will open the UNKNOWN file extension. You simply download and install the OpenWith program, choose the file you want to open, and then click on the option. The program will automatically search for the appropriate free program to open this file type. If there is a list of programs, you can choose the one you want to use and download it to your PC.