Opening UNDEFINED files

Did your computer fail to open an UNDEFINED file? We explain what UNDEFINED files are and recommend software that we know can open or convert your UNDEFINED files.

What is an UNDEFINED file?

The .undefined file extension is used for various file formats that cannot be recognized by the system. Some file recovery tools use this file extension to label recovered files that have not been completely restored. Other programs like Web browsers and email applications may label downloaded or attached files with unknown file types as UNDEFINED files.

The content of these .undefined files varies, depending on the actual format of the files. For example, a data recovery application that has failed to completely restore a JPG file may label the file as an UNDEFINED file, and this .undefined file may contain corrupted image data. On the other hand, a Web browser that fails to recognize an AVI file that has been downloaded from the Internet may label the digital video file as an UNDEFINED file. This .undefined file may contain digital video, but there is no guarantee that the .undefined file will play in a standard AVI player.

It's best to leave these .undefined files alone. In most instances, these UNDEFINED files contain corrupted data and are from unknown sources.

Try a universal file viewer

In addition to the products listed above, I would suggest that you try a universal file viewer like Free File Viewer. It can open over 200 different types of files - and very likely yours too! Download Free File Viewer.

By Prof. Jones (The File Expert)

Chief Content Editor and File Expert

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