This option should be set before editing a binary file. You can also use the |-b| Vim argument. When this option is switched on a few options will be changed (also when it already was on): 'textwidth' will be set to 0 'wrapmargin' will be set to 0 'modeline' will be off 'expandtab' will be off Also, 'fileformat' and 'fileformats' options will not be used, the file is read and written like 'fileformat' was "unix" (a single separates lines). The 'fileencoding' and 'fileencodings' options will not be used, the file is read without conversion. NOTE: When you start editing a(nother) file while the 'bin' option is on, settings from autocommands may change the settings again (e.g., 'textwidth'), causing trouble when editing. You might want to set 'bin' again when the file has been loaded. The previous values of these options are remembered and restored when 'bin' is switched from on to off. Each buffer has its own set of saved option values. To edit a file with 'binary' set you can use the |++bin| argument. This avoids you have to do ":set bin", which would have effect for all files you edit. When writing a file the for the last line is only written if there was one in the original file (normally Vim appends an to the last line if there is none; this would make the file longer). See the 'endofline' option.