Gnumeric stores its information by creating files and re-opening these files during a future session. Saving information to files also allows a user to send the information to others.
The default file format for Gnumeric is based on the eXtensible Markup Language (XML). By default, files are saved as text files, consisting of XML, which are then compressed using the library of the gzip program. The extension for Gnumeric files is .gnumeric on platforms which support file extensions of any size, .gnum for systems which restrict extensions to four letters, or .gnm for systems which restrict extensions to three letters.
Gnumeric can also open or save files in a number of other file formats. The project prides itself for the work reverse engineering and supporting the file formats used by Microsoft Excel. Gnumeric can use the Excel file format as if it were the native file format, meaning that Gnumeric can store and retrieve essentially every aspect of a worksheet using the Excel format. Similarly, Gnumeric supports the OASIS Open Document Format for Office Applications (ODF 1.2) file format (ISO/IEC 26300:2006/Amd 1:2012) as well as the ECMA 376 2nd Edition file format (ISO/IEC 29500:2008) as if they were the native format.
Gnumeric cannot delete files from the file system. Gnumeric can open existing files and create new files but cannot delete files once they are created. Files can be deleted using a file browser such as Nautilus on the GNOME desktop or using the command-line program rm.
This chapter discusses working with actual files. It is also possible to import data into Gnumeric using the clipboard by copying either text or html table information in another program and then pasting the resulting data into a worksheet. See Section 5.7.4 ― Cut and Paste Between Gnumeric and Other Applications for details.
Text files are often used to store data, using many different systems to structure the data such as using commas, tabs or spaces to separate values. Gnumeric features a flexible system that enables users to define exactly the structure of the text file to be imported or exported.
Gnumeric can be integrated with an email client to allow files to be sent directly as attachments to an electronic mail message.
Gnumeric also features a command-line tool called ssconvert to convert files between any of the file formats which it supports.