Popular formats

undefined 

Opening undefined files

Have a problem opening a .undefined file? We collect information about file formats and can explain what undefined files are. Additionally we recommend software suitable for opening or converting such files.

What is the .UNDEFINED file type?

All occurrences of the .undefined extension have to do with software bugs and possibly improper configuration. The .undefined extension itself, when assigned to a file, is an indication of a program's failure to recognize a particular file format and/or assign a proper extension.

The .undefined extension could be appended to media files like MP3 (instead of the proper .mp3 in this case) downloaded from some online FFMPEG-based audio/video conversion services, due to improper configuration or software bugs. If the target file format/type is known, one may attempt to manually change the extension (i.e., .undefined to .mp3).

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Software to open or convert UNDEFINED files

You can open undefined files with the following programs: