diff --git a/README.md b/README.md
index 05a4bbc..75a0626 100644
--- a/README.md
+++ b/README.md
@@ -110,16 +110,23 @@ through [README-VIM][README-VIM] to learn more about them.
 
 #### Preview window
 
-If the width of the screen is wider than 120 columns, some commands will show
-the preview window on the right. You can customize the behavior with
-`g:fzf_preview_window`. Here are some examples:
+Some commands will show the preview window on the right. You can customize the
+behavior with `g:fzf_preview_window`. Here are some examples:
 
 ```vim
-" Empty value to disable preview window altogether
-let g:fzf_preview_window = ''
+" This is the default option:
+"   - Preview window on the right with 50% width
+"   - CTRL-/ will toggle preview window.
+" - Note that this array is passed as arguments to fzf#vim#with_preview function.
+" - To learn more about preview window options, see `--preview-window` section of `man fzf`.
+let g:fzf_preview_window = ['right:50%', 'ctrl-/']
 
-" Always enable preview window on the right with 60% width
-let g:fzf_preview_window = 'right:60%'
+" Preview window on the upper side of the window with 40% height,
+" hidden by default, ctrl-/ to toggle
+let g:fzf_preview_window = ['up:40%:hidden', 'ctrl-/']
+
+" Empty value to disable preview window altogether
+let g:fzf_preview_window = []
 ```
 
 ### Command-local options
diff --git a/autoload/fzf/vim.vim b/autoload/fzf/vim.vim
index 91cfa07..3a2d653 100644
--- a/autoload/fzf/vim.vim
+++ b/autoload/fzf/vim.vim
@@ -155,7 +155,9 @@ function! fzf#vim#with_preview(...)
   else
     let preview_cmd = fzf#shellescape(s:bin.preview)
   endif
-  let preview += ['--preview', preview_cmd.' '.placeholder]
+  if len(placeholder)
+    let preview += ['--preview', preview_cmd.' '.placeholder]
+  end
 
   if len(args)
     call extend(preview, ['--bind', join(map(args, 'v:val.":toggle-preview"'), ',')])
diff --git a/doc/fzf-vim.txt b/doc/fzf-vim.txt
index b32ae75..29807d8 100644
--- a/doc/fzf-vim.txt
+++ b/doc/fzf-vim.txt
@@ -1,4 +1,4 @@
-fzf-vim.txt	fzf-vim	Last change: August 12 2020
+fzf-vim.txt	fzf-vim	Last change: October 22 2020
 FZF-VIM - TABLE OF CONTENTS                                *fzf-vim* *fzf-vim-toc*
 ==============================================================================
 
@@ -175,15 +175,22 @@ Preview window~
 
                                                           *g:fzf_preview_window*
 
-If the width of the screen is wider than 120 columns, some commands will show
-the preview window on the right. You can customize the behavior with
-`g:fzf_preview_window`. Here are some examples:
+Some commands will show the preview window on the right. You can customize the
+behavior with `g:fzf_preview_window`. Here are some examples:
 >
-    " Empty value to disable preview window altogether
-    let g:fzf_preview_window = ''
+    " This is the default option:
+    "   - Preview window on the right with 50% width
+    "   - CTRL-/ will toggle preview window.
+    " - Note that this array is passed as arguments to fzf#vim#with_preview function.
+    " - To learn more about preview window options, see `--preview-window` section of `man fzf`.
+    let g:fzf_preview_window = ['right:50%', 'ctrl-/']
 
-    " Always enable preview window on the right with 60% width
-    let g:fzf_preview_window = 'right:60%'
+    " Preview window on the upper side of the window with 40% height,
+    " hidden by default, ctrl-/ to toggle
+    let g:fzf_preview_window = ['up:40%:hidden', 'ctrl-/']
+
+    " Empty value to disable preview window altogether
+    let g:fzf_preview_window = []
 <
 
 < Command-local options >_____________________________________________________~
diff --git a/plugin/fzf.vim b/plugin/fzf.vim
index 2565d40..55cb61c 100644
--- a/plugin/fzf.vim
+++ b/plugin/fzf.vim
@@ -39,27 +39,32 @@ function! s:defs(commands)
   endfor
 endfunction
 
-function! s:p(bang, ...)
-  let preview_window = get(g:, 'fzf_preview_window', a:bang && &columns >= 80 || &columns >= 120 ? 'right': '')
-  if len(preview_window)
-    return call('fzf#vim#with_preview', add(copy(a:000), preview_window))
+function! s:p(...)
+  let preview_args = get(g:, 'fzf_preview_window', ['right', 'ctrl-/'])
+  if empty(preview_args)
+    return { 'options': ['--preview-window', 'hidden'] }
   endif
-  return {}
+
+  " For backward-compatiblity
+  if type(preview_args) == type('')
+    let preview_args = [preview_args]
+  endif
+  return call('fzf#vim#with_preview', extend(copy(a:000), preview_args))
 endfunction
 
 call s:defs([
-\'command!      -bang -nargs=? -complete=dir Files       call fzf#vim#files(<q-args>, s:p(<bang>0), <bang>0)',
-\'command!      -bang -nargs=? GitFiles                  call fzf#vim#gitfiles(<q-args>, <q-args> == "?" ? {} : s:p(<bang>0), <bang>0)',
-\'command!      -bang -nargs=? GFiles                    call fzf#vim#gitfiles(<q-args>, <q-args> == "?" ? {} : s:p(<bang>0), <bang>0)',
-\'command! -bar -bang -nargs=? -complete=buffer Buffers  call fzf#vim#buffers(<q-args>, s:p(<bang>0, { "placeholder": "{1}" }), <bang>0)',
+\'command!      -bang -nargs=? -complete=dir Files       call fzf#vim#files(<q-args>, s:p(), <bang>0)',
+\'command!      -bang -nargs=? GitFiles                  call fzf#vim#gitfiles(<q-args>, s:p(<q-args> == "?" ? { "placeholder": "" } : {}), <bang>0)',
+\'command!      -bang -nargs=? GFiles                    call fzf#vim#gitfiles(<q-args>, s:p(<q-args> == "?" ? { "placeholder": "" } : {}), <bang>0)',
+\'command! -bar -bang -nargs=? -complete=buffer Buffers  call fzf#vim#buffers(<q-args>, s:p({ "placeholder": "{1}" }), <bang>0)',
 \'command!      -bang -nargs=* Lines                     call fzf#vim#lines(<q-args>, <bang>0)',
 \'command!      -bang -nargs=* BLines                    call fzf#vim#buffer_lines(<q-args>, <bang>0)',
 \'command! -bar -bang Colors                             call fzf#vim#colors(<bang>0)',
-\'command!      -bang -nargs=+ -complete=dir Locate      call fzf#vim#locate(<q-args>, s:p(<bang>0), <bang>0)',
-\'command!      -bang -nargs=* Ag                        call fzf#vim#ag(<q-args>, s:p(<bang>0), <bang>0)',
-\'command!      -bang -nargs=* Rg                        call fzf#vim#grep("rg --column --line-number --no-heading --color=always --smart-case -- ".shellescape(<q-args>), 1, s:p(<bang>0), <bang>0)',
+\'command!      -bang -nargs=+ -complete=dir Locate      call fzf#vim#locate(<q-args>, s:p(), <bang>0)',
+\'command!      -bang -nargs=* Ag                        call fzf#vim#ag(<q-args>, s:p(), <bang>0)',
+\'command!      -bang -nargs=* Rg                        call fzf#vim#grep("rg --column --line-number --no-heading --color=always --smart-case -- ".shellescape(<q-args>), 1, s:p(), <bang>0)',
 \'command!      -bang -nargs=* Tags                      call fzf#vim#tags(<q-args>, <bang>0)',
-\'command!      -bang -nargs=* BTags                     call fzf#vim#buffer_tags(<q-args>, s:p(<bang>0, { "placeholder": "{2}:{3}" }), <bang>0)',
+\'command!      -bang -nargs=* BTags                     call fzf#vim#buffer_tags(<q-args>, s:p({ "placeholder": "{2}:{3}" }), <bang>0)',
 \'command! -bar -bang Snippets                           call fzf#vim#snippets(<bang>0)',
 \'command! -bar -bang Commands                           call fzf#vim#commands(<bang>0)',
 \'command! -bar -bang Marks                              call fzf#vim#marks(<bang>0)',
@@ -69,7 +74,7 @@ call s:defs([
 \'command! -bar -bang BCommits                           call fzf#vim#buffer_commits(<bang>0)',
 \'command! -bar -bang Maps                               call fzf#vim#maps("n", <bang>0)',
 \'command! -bar -bang Filetypes                          call fzf#vim#filetypes(<bang>0)',
-\'command!      -bang -nargs=* History                   call s:history(<q-args>, s:p(<bang>0), <bang>0)'])
+\'command!      -bang -nargs=* History                   call s:history(<q-args>, s:p(), <bang>0)'])
 
 function! s:history(arg, extra, bang)
   let bang = a:bang || a:arg[len(a:arg)-1] == '!'