diff --git a/autoload/xolox/easytags.vim b/autoload/xolox/easytags.vim
index 2088f48..0d6e857 100644
--- a/autoload/xolox/easytags.vim
+++ b/autoload/xolox/easytags.vim
@@ -99,8 +99,11 @@ function! xolox#easytags#update(silent, filter_tags, filenames) " {{{2
     let tagsfile = xolox#easytags#get_tagsfile()
     let firstrun = !filereadable(tagsfile)
     let cmdline = s:prep_cmdline(cfile, tagsfile, firstrun, a:filenames, context)
-    let output = s:run_ctags(starttime, cfile, tagsfile, firstrun, cmdline)
+    let [output, has_updates] = s:run_ctags(starttime, cfile, tagsfile, firstrun, cmdline)
     if !firstrun
+      if !has_updates
+        return 1
+      endif
       if have_args && !empty(g:easytags_by_filetype)
         " TODO Get the headers from somewhere?!
         call s:save_by_filetype(a:filter_tags, [], output, context)
@@ -201,12 +204,41 @@ function! s:prep_cmdline(cfile, tagsfile, firstrun, arguments, context) " {{{3
   return have_args ? join(cmdline) : ''
 endfunction
 
+if exists('*sha256')
+function! s:get_fingerprint(cfile, output)
+  return sha256(a:output)
+endfunction
+else
+function! s:get_fingerprint(cfile, output)
+  " Don't want to re-implement a costly hashing function in Vimscript. Just
+  " handle files that never had any tags.
+  if empty(a:output)
+    return get(s:fingerprints, a:cfile, 1)
+  else
+    return ''
+  endif
+endfunction
+endif
+
+let s:fingerprints = {}
+function! s:has_updates(cfile, output)
+  let fingerprint = s:get_fingerprint(a:cfile, a:output)
+  if ! empty(fingerprint) && get(s:fingerprints, a:cfile, '') ==# fingerprint
+    return 0
+  endif
+
+  let s:fingerprints[a:cfile] = fingerprint
+  return 1
+endfunction
+
 function! s:run_ctags(starttime, cfile, tagsfile, firstrun, cmdline) " {{{3
   let lines = []
+  let has_updates = 1
   if a:cmdline != ''
     call xolox#misc#msg#debug("easytags.vim %s: Executing %s.", g:xolox#easytags#version, a:cmdline)
     try
       let lines = xolox#shell#execute(a:cmdline, 1)
+      let has_updates = a:firstrun || s:has_updates(a:cfile, join(lines, "\n"))
     catch /^Vim\%((\a\+)\)\=:E117/
       " Ignore missing shell.vim plug-in.
       let output = system(a:cmdline)
@@ -215,6 +247,7 @@ function! s:run_ctags(starttime, cfile, tagsfile, firstrun, cmdline) " {{{3
         throw printf(msg, fnamemodify(a:tagsfile, ':~'), strtrans(output))
       endif
       let lines = split(output, "\n")
+      let has_updates = a:firstrun || s:has_updates(a:cfile, output)
     endtry
     if a:firstrun
       if a:cfile != ''
@@ -225,7 +258,7 @@ function! s:run_ctags(starttime, cfile, tagsfile, firstrun, cmdline) " {{{3
       return []
     endif
   endif
-  return xolox#easytags#parse_entries(lines)
+  return [xolox#easytags#parse_entries(lines), has_updates]
 endfunction
 
 function! s:filter_merge_tags(filter_tags, tagsfile, output, context) " {{{3