diff --git a/lua/hardline.lua b/lua/hardline.lua
index deedb69..b9c8eb7 100644
--- a/lua/hardline.lua
+++ b/lua/hardline.lua
@@ -16,8 +16,9 @@ M.options = {
     {class = 'high', item = require('hardline.parts.git').get_item},
     {class = 'med', item = require('hardline.parts.filename').get_item},
     {class = 'med', item ='%='},
-    {class = 'warning', item = require('hardline.parts.lsp').get_warning},
     {class = 'error', item = require('hardline.parts.lsp').get_error},
+    {class = 'warning', item = require('hardline.parts.lsp').get_warning},
+    {class = 'warning', item = require('hardline.parts.whitespace').get_item},
     {class = 'high', item = require('hardline.parts.filetype').get_item},
     {class = 'mode', item = require('hardline.parts.line').get_item},
   },
diff --git a/lua/hardline/common.lua b/lua/hardline/common.lua
index 60f9f39..545042c 100644
--- a/lua/hardline/common.lua
+++ b/lua/hardline/common.lua
@@ -1,3 +1,5 @@
+local cmd, fn, vim = vim.cmd, vim.fn, vim
+local g = vim.g
 local M = {
   modes = {
     ['?'] = {text = '???', color = 'inactive'},
@@ -16,13 +18,13 @@ local M = {
 }
 
 function M.echo(hlgroup, msg)
-  vim.cmd(string.format('echohl %s', hlgroup))
-  vim.cmd(string.format('echo "[hardline] %s"', msg))
-  vim.cmd('echohl None')
+  cmd(string.format('echohl %s', hlgroup))
+  cmd(string.format('echo "[hardline] %s"', msg))
+  cmd('echohl None')
 end
 
 function M.is_active()
-  return vim.g.statusline_winid == vim.fn.win_getid()
+  return g.statusline_winid == fn.win_getid()
 end
 
 return M
diff --git a/lua/hardline/parts/filename.lua b/lua/hardline/parts/filename.lua
index 7d44e31..4c80dd9 100644
--- a/lua/hardline/parts/filename.lua
+++ b/lua/hardline/parts/filename.lua
@@ -1,5 +1,7 @@
+local fn = vim.fn
+
 local function get_item()
-  local name = vim.fn.expand('%:~:.')
+  local name = fn.expand('%:~:.')
   return table.concat({' ', '%<', name, ' '})
 end
 
diff --git a/lua/hardline/parts/filetype.lua b/lua/hardline/parts/filetype.lua
index 427c1ba..9ada887 100644
--- a/lua/hardline/parts/filetype.lua
+++ b/lua/hardline/parts/filetype.lua
@@ -1,5 +1,7 @@
+local bo = vim.bo
+
 local function get_filetype()
-  return string.format('%s', vim.bo.filetype)
+  return string.format('%s', bo.filetype)
 end
 
 local function get_item()
diff --git a/lua/hardline/parts/git.lua b/lua/hardline/parts/git.lua
index fcd2252..8cb1dfb 100644
--- a/lua/hardline/parts/git.lua
+++ b/lua/hardline/parts/git.lua
@@ -1,6 +1,9 @@
+local fn = vim.fn
+local g = vim.g
+
 local function get_hunks()
-  if not vim.g.loaded_gitgutter then return '' end
-  local summary = vim.fn.GitGutterGetHunkSummary()
+  if not g.loaded_gitgutter then return '' end
+  local summary = fn.GitGutterGetHunkSummary()
   return table.concat({
     string.format('+%d', summary[1]), ' ',
     string.format('~%d', summary[2]), ' ',
@@ -9,8 +12,8 @@ local function get_hunks()
 end
 
 local function get_branch()
-  if not vim.g.loaded_gitgutter then return '' end
-  return string.format('(%s)', vim.fn.FugitiveHead())
+  if not g.loaded_gitgutter then return '' end
+  return string.format('(%s)', fn.FugitiveHead())
 end
 
 local function get_item()
diff --git a/lua/hardline/parts/line.lua b/lua/hardline/parts/line.lua
index 2b51bf6..526c331 100644
--- a/lua/hardline/parts/line.lua
+++ b/lua/hardline/parts/line.lua
@@ -1,4 +1,4 @@
-local common = require('hardline.common')
+local fn = vim.fn
 
 local function get_dots(current, max)
   current = string.len(tostring(current))
@@ -7,23 +7,23 @@ local function get_dots(current, max)
 end
 
 local function get_line()
-  local nb_lines = vim.fn.line('$')
-  local line = vim.fn.line('.')
+  local nb_lines = fn.line('$')
+  local line = fn.line('.')
   local dots = get_dots(line, nb_lines)
   return string.format('%s%d/%d', dots, line, nb_lines)
 end
 
 local function get_column()
-  local nb_columns = vim.fn.col('$') - 1
-  local column = vim.fn.col('.')
+  local nb_columns = fn.col('$') - 1
+  local column = fn.col('.')
   local max_dots = get_dots(nb_columns, 999)
   local dots = get_dots(column, 999)
   return string.format('|%s%d/%s%d', dots, column, max_dots, nb_columns)
 end
 
 local function get_percent()
-  local nb_lines = vim.fn.line('$')
-  local line = vim.fn.line('.')
+  local nb_lines = fn.line('$')
+  local line = fn.line('.')
   local percent = math.floor(line * 100 / nb_lines)
   local dots = get_dots(percent, 100)
   return string.format('|%s%d%%%%', dots, percent)
diff --git a/lua/hardline/parts/lsp.lua b/lua/hardline/parts/lsp.lua
index e6d0e83..6cb87b4 100644
--- a/lua/hardline/parts/lsp.lua
+++ b/lua/hardline/parts/lsp.lua
@@ -1,6 +1,8 @@
+local lsp, vim = vim.lsp, vim
+
 local function get_diagnostic(prefix, severity)
-  if vim.tbl_isempty(vim.lsp.buf_get_clients(0)) then return '' end
-  local count = vim.lsp.diagnostic.get_count(0, severity)
+  if vim.tbl_isempty(lsp.buf_get_clients(0)) then return '' end
+  local count = lsp.diagnostic.get_count(0, severity)
   if count < 1 then return '' end
   return table.concat({' ', string.format('%s:%d', prefix, count), ' '})
 end
diff --git a/lua/hardline/parts/mode.lua b/lua/hardline/parts/mode.lua
index 0eee386..7bf8dd0 100644
--- a/lua/hardline/parts/mode.lua
+++ b/lua/hardline/parts/mode.lua
@@ -1,17 +1,19 @@
+local fn = vim.fn
+local o, bo, wo = vim.o, vim.bo, vim.wo
 local common = require('hardline.common')
 
 local function get_mode()
-  return common.modes[vim.fn.mode()].text
+  return common.modes[fn.mode()].text
 end
 
 local function get_paste()
-  if not vim.o.paste then return '' end
+  if not o.paste then return '' end
   return '|PASTE'
 end
 
 local function get_spell()
-  if not vim.wo.spell then return '' end
-  return string.format('|SPELL[%s]', string.upper(vim.bo.spelllang))
+  if not wo.spell then return '' end
+  return string.format('|SPELL[%s]', string.upper(bo.spelllang))
 end
 
 local function get_item()
diff --git a/lua/hardline/parts/whitespace.lua b/lua/hardline/parts/whitespace.lua
index ce84ef3..1a45cfd 100644
--- a/lua/hardline/parts/whitespace.lua
+++ b/lua/hardline/parts/whitespace.lua
@@ -1,8 +1,72 @@
-local M = {}
+local cmd, fn, vim = vim.cmd, vim.fn, vim
+local bo = vim.bo
+local enabled = false
+local options = {
+  c_langs = {'arduino', 'c', 'cpp', 'cuda', 'go', 'javascript', 'ld', 'php'},
+  max_lines = 5000,
+  timeout = 100,
+}
 
-function M.get_item()
-  return table.concat({
-  })
+local function search(prefix, pattern)
+  local line = fn.search(pattern, 'nw', 0, options.timeout)
+  if line == 0 then return '' end
+  return string.format('[%s:%d]', prefix, line)
 end
 
-return M
+local function check_trailing()
+  return search('trailing', [[\s$]])
+end
+
+local function check_mixed_indent()
+  local tst = [[(^\t* +\t\s*\S)]]
+  local tls = string.format([[(^\t+ {%d,}\S)]], bo.tabstop)
+  local pattern = string.format([[\v%s|%s]], tst, tls)
+  return search('mix-indent', pattern)
+end
+
+local function check_mixed_indent_file()
+  local head_spc = [[\v(^ +)]]
+  if vim.tbl_contains(options.c_langs, bo.filetype) then
+    head_spc = [[\v(^ +\*@!)]]
+  end
+  local indent_tabs = fn.search([[\v(^\t+)]], 'nw', 0, options.timeout)
+  local indent_spc = fn.search(head_spc, 'nw', 0, options.timeout)
+  if indent_tabs == 0 or indent_spc == 0 then return '' end
+  return string.format('[mix-indent-file:%d,%d]', indent_spc, indent_tabs)
+end
+
+local function check_conflict()
+  local annotation = [[\%([0-9A-Za-z_.:]\+\)\?]]
+  local raw_pattern = [[^\%%(\%%(<\{7} %s\)\|\%%(=\{7\}\)\|\%%(>\{7\} %s\)\)$]]
+  if bo.filetype == 'rst' then
+    raw_pattern = [[^\%%(\%%(<\{7} %s\)\|\%%(>\{7\} %s\)\)$]]
+  end
+  local pattern = string.format(raw_pattern, annotation, annotation)
+  return search('conflict', pattern)
+end
+
+local function get_item()
+  if not enabled then
+    cmd 'augroup hardline_whitespace'
+    cmd 'autocmd!'
+    cmd 'autocmd CursorHold, BufWritePost * unlet! b:hardline_whitespace'
+    cmd 'augroup end'
+    enabled = true
+  end
+  if bo.readonly or not bo.modifiable then return '' end
+  if fn.line('$') > options.max_lines then return '' end
+  if fn.exists('b:hardline_whitespace') ~= 0 then return '' end
+  local item = table.concat({
+    ' ',
+    check_trailing(),
+    check_mixed_indent(),
+    check_mixed_indent_file(),
+    check_conflict(),
+    ' ',
+  })
+  return item == '  ' and '' or item
+end
+
+return {
+  get_item = get_item,
+}