But sometimes I just got some base64 raw string like aGFwcHkgdmltbWluZyA=. Here is how to use a system command to read it in Vim directly. You need a program like decode64.exe to encode/decode strings. You can can download it from (unfortunately I tested it under WIN2K/2003 only). Put the decode64.exe/base64dll.dll somewhere in your %path% enviroment variable. You need write some script in your vimrc: Now open a new gvim instance and copy and paste aGFwcHkgdmltbWluZyA= into it. Use virtual mode to select it, then press ;mmd :set enc=utf8 first. See [help 'enc'].