How to Open a File With No Extension

How can you open a file that has no extension? What if it has an extension, but you don’t know what type of file it is? It is useless to know the extension of a file if you have no idea of ​​the format it uses or of the programs that are compatible.

In today’s post we will see two procedures that will help you solve these unknowns:

  • How to see the extension of a file, even if it is hidden or has been deleted.
  • What program to use to open an unknown file.

How to see the extension of a file

When you cannot see the extension of a file at first glance, there are two options:

  1. either the extension is hidden due to the configuration of Windows (or the operating system that you are using),
  2. or the extension of the file has been removed.

In this second case, you will have to test your investigative skills, which will take you a little more time to solve the mystery (but don’t worry, it’s not as complicated as it seems at first glance).

Hidden extension

So before we start, let’s make sure that the extension is not hidden due to Windows settings.

Note: For this example, we will use a PC with Windows 11. If you have Windows 10 or an earlier version, the steps to follow are practically the same.

  • Open Windows File Explorer.
  • In the top menu, click on the 3-dot dropdown that you will see on the right and select “ Options ”. If you have Windows 10 you can open the folder options from “View -> Options -> Change folder options”.
  • Within the folder options, click on the “ View ” tab.
  • Make sure the “ Hide file extensions for known file types ” checkbox is unchecked.hide extensions for file types
  • Click on the “Apply” button to save the changes.

If the extension was hidden now, you will see what the file extension is.

Alternatively, you can also right-click on the file, select “Properties”, and view its extension in the “File Type” field.

No extension

If the file still doesn’t show an extension, it may simply be because the extension was manually removed, either accidentally or on purpose.

To solve this, you need a hex editor. You can install a free editor like HxD (a freeware program that you can download and install from the author’s website ) or use an online hexadecimal editor like , which works from the browser without the need to install anything on the PC.

  • For this example, we will use the online editor, so open the browser and go to .
  • In the upper menu, click on “ Open file ” and select the unknown file you want to analyze.
  • Once the file is open, look at the first line of code where you can see the extension or file type of the file in question.

If you don’t see the file extension on the first line, you may find it throughout the document.

It is also interesting to mention that this “trick” does not work with all types of files. In the case of Word, for example, Microsoft uses the XML format, which is the same as that used in .docx or .xlsx files.

If this happens to you, the best thing you can do is use Toolsey. This is an online tool that analyzes any file and tells you what its extension is and what type of file it is.

  • First, open your browser and go to the Toolsey website.
  • Click on “Select a File”.
  • Upload the file you want to analyze.
  • Toolsey will automatically show you a box with the file type of the selected to open a file with no extension

For multiple unknown files

Finally, if you have several unknown files, instead of having to analyze them one by one with Toolsey, you can also download the DROID program. It is free, open-source software for PCs developed by the UK Government, and can be obtained from its GitHub repository. With DROID, you will have the advantage that it allows you to analyze more than one file at once.

How to find a compatible program to open the file

Now that you know the file extension, you can use the corresponding program to open it and view its content. If you still don’t know what program to use to open it, you can use another online tool, such as

All you have to do is enter the page and enter the extension of your file to see relevant information about it, as well as a list of the compatible programs that you can use to work with this type of file.

If you don’t know what the file extension is, you can also drag the file to the browser so that FileInfo loads it and analyzes it directly.

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