Files with the UNK extension are a type of UVProbe Data File developed for the UVProbe software program by Shimadzu Scientific Instruments. The UNK file extension is compatible with Windows. The developer website states that UVProbe software supports UNK files. Windows 10 users in the United States who use Google Chrome, most commonly use UNK files. The file type is categorized under the Misc Files subset comprising 6033 various formats. Although they may contain viruses, UNK files can be opened if certain of their content. For Windows and Mac operating systems, associate UNK files with the proper application. On Windows, right click a UNK file to bring up the options “Open With” and “Choose another app”. On Mac, right click to select “Open With” and “Other” to set the desired default program. An alternative use of UNK files is as a Lotus Notes Unknown Attachment. Opening newer versions of the .UNK file format requires latest software as older programs may no longer support them. Additionally, scan UNK files with antivirus software before attempting to open them.