What Is a CGI File?

A file with the CGI file extension is a Common Gateway Interface Script file. They are text files but since they're written in a programming language like C or Perl, they can function as executable files under certain conditions.

One example is a CGI file that holds scripts that are responsible for sending email from a form on a website. These script files are often seen in a web server's "cgi-bin" directory.

Since CGI files are text files, the built-in Notepad program in Windows can be used to view and edit them. But other text editors can be used to open CGI files as well.

Although it's not intended to work this way, you may sometimes try to download a file from a website but will instead get a .CGI file. For example, a bank statement or insurance bill you're downloading may come as a .CGI file instead of a PDF file (or some other format like JPG, etc.).

You should be able to rename the .CGI file to the file you were intending to download, and then be able to open it like you regularly would. In this example, renaming the .CGI file to a .PDF file should let you open the PDF in a PDF viewer. The same process should work with any file in this context that's improperly named.

If you keep getting a .CGI file instead of the actual file you're after, it may be necessary to clear the browser's cache and try again. Disabling your firewall or security software may be another solution if the problem persists.

If you find that an application on your computer tries to open the CGI file but it's the wrong application or you'd rather have another installed program open CGI files, change the default program for a specific file extension to make that change in Windows.

CGI files won't work properly on a web server if you convert it to another format. However, you can still save an open CGI file to HTML or another text-based format using a text editor we linked to above.

Remember what we said above about renaming a CGI file. Doing so doesn't actually convert the CGI to PDF, JPG, etc., but instead just puts the proper file extension on the file so that the right program will recognize and open it. An actual file conversion takes place with a file converter.

Double-check the file extension to make sure you aren't confusing a CGM (Computer Graphics Metafile), CSI, CGR (CATIA Graphical Representation), CGF (Crytek Geometry Format), or CGZ (Cube Map) file with a file that has the .CGI extension.

As you can see, file extensions used between different formats can look an awful lot alike, but that doesn't necessarily mean that they're opened or converted in the same way.