A PRN file contains instructions for a printer, which includes the content to be printed, the number of pages to print, the paper size, and the printer tray to use. It is created by choosing "Print to File" within the Print dialog box in a Windows or macOS program. PRN files are similar to PostScript (.PS) files.

PRN files may be printed in Mac OS X by dragging the file to the desktop printer icon. In Windows, they can be printed by right-clicking the file and selecting "Microsoft Office Document Imaging" (only some versions of Microsoft Office Document Imaging support PRN files). You may also open them via the Windows command line. To do this, select "Run" from the Start Menu, type "cmd," and perform the following steps: If the printer is connected via USB, type: "COPY /B [filename.prn] \\[Computer Name]\[Shared Printer Name]" If the printer is connected via an older parallel port connection, type: "COPY /B [filename.prn] LPT1:" NOTE: Do not include the [brackets] when typing the actual command. You can also rename the PRN file as an .XPS file and open it with various programs, such as Microsoft XPS Viewer, Pagemark XpsViewer, and NiXPS View. To rename the file, select the filename and rename .prn to .xps. You may open a PRN file with a text editor, such as Microsoft Notepad or Apple TextEdit. The file stores the text to be printed as plain text but the printing instructions consist of printer codes, which should not be modified or else you will encounter printer errors.