.2011 is Any data file created in 2011
Key Features: .2011 File Extension
What is an .2011 file?
The 2011 file extension might be used for any data file created in year 2018, typically as some kind of backup to distinguish the data from previous years.
Such files are most frequently used by various tax preparation software, but might as well contain calendar, business or just be backup of some sort.
This 2011 file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.