diff --git a/src/calibre/gui2/tweak_book/__init__.py b/src/calibre/gui2/tweak_book/__init__.py
index e4a6586c94..1f2f5fa1bc 100644
--- a/src/calibre/gui2/tweak_book/__init__.py
+++ b/src/calibre/gui2/tweak_book/__init__.py
@@ -39,6 +39,7 @@ d['preview_minimum_font_size'] = 8
 d['remove_existing_links_when_linking_sheets'] = True
 d['charmap_favorites'] = list(map(ord, '\xa0\u2002\u2003\u2009\xad' '‘’“”‹›«»‚„' '—–§¶†‡©®™' '→⇒•·°±−×÷¼½½¾' '…µ¢£€¿¡¨´¸ˆ˜' 'ÀÁÂÃÄÅÆÇÈÉÊË' 'ÌÍÎÏÐÑÒÓÔÕÖØ' 'ŒŠÙÚÛÜÝŸÞßàá' 'âãäåæçèéêëìí' 'îïðñòóôõöøœš' 'ùúûüýÿþªºαΩ∞'))  # noqa
 d['folders_for_types'] = {'style':'styles', 'image':'images', 'font':'fonts', 'audio':'audio', 'video':'video'}
+d['pretty_print_on_open'] = False
 
 del d
 
diff --git a/src/calibre/gui2/tweak_book/boss.py b/src/calibre/gui2/tweak_book/boss.py
index 28a091158a..99fa96c094 100644
--- a/src/calibre/gui2/tweak_book/boss.py
+++ b/src/calibre/gui2/tweak_book/boss.py
@@ -1086,6 +1086,8 @@ class Boss(QObject):
                 data = use_template
             editor = editors[name] = editor_from_syntax(syntax, self.gui.editor_tabs)
             self.init_editor(name, editor, data, use_template=bool(use_template))
+            if tprefs['pretty_print_on_open']:
+                editor.pretty_print(name)
         self.show_editor(name)
         return editor
 
diff --git a/src/calibre/gui2/tweak_book/editor/image.py b/src/calibre/gui2/tweak_book/editor/image.py
index 070c36bc47..60a1c7a1de 100644
--- a/src/calibre/gui2/tweak_book/editor/image.py
+++ b/src/calibre/gui2/tweak_book/editor/image.py
@@ -136,6 +136,9 @@ class Editor(QMainWindow):
     def number_of_lines(self):
         return 0
 
+    def pretty_print(self, name):
+        return False
+
     def get_raw_data(self):
         return self.canvas.get_image_data(quality=self.quality)
 
diff --git a/src/calibre/gui2/tweak_book/editor/widget.py b/src/calibre/gui2/tweak_book/editor/widget.py
index 7f5b423223..ea21c4737e 100644
--- a/src/calibre/gui2/tweak_book/editor/widget.py
+++ b/src/calibre/gui2/tweak_book/editor/widget.py
@@ -283,7 +283,10 @@ class Editor(QMainWindow):
         from calibre.ebooks.oeb.polish.pretty import pretty_html, pretty_css, pretty_xml
         if self.syntax in {'css', 'html', 'xml'}:
             func = {'css':pretty_css, 'xml':pretty_xml}.get(self.syntax, pretty_html)
-            self.editor.replace_text(func(current_container(), name, unicode(self.editor.toPlainText())).decode('utf-8'))
+            original_text = unicode(self.editor.toPlainText())
+            prettied_text = func(current_container(), name, original_text).decode('utf-8')
+            if original_text != prettied_text:
+                self.editor.replace_text(prettied_text)
             return True
         return False
 
diff --git a/src/calibre/gui2/tweak_book/preferences.py b/src/calibre/gui2/tweak_book/preferences.py
index 8d07fc7221..c605765463 100644
--- a/src/calibre/gui2/tweak_book/preferences.py
+++ b/src/calibre/gui2/tweak_book/preferences.py
@@ -184,6 +184,13 @@ class EditorSettings(BasicSettings):
         lw.setText(_('Show the name of the current character before the cursor along with the line and column number'))
         l.addRow(lw)
 
+        lw = self('pretty_print_on_open')
+        lw.setText(_('Beautify individual files automatically when they are opened'))
+        lw.setToolTip('<p>' + _(
+            'This will cause the beautify current file action to be performed automatically every'
+            ' time you open a HTML/CSS/etc. file for editing.'))
+        l.addRow(lw)
+
 class IntegrationSettings(BasicSettings):
 
     def __init__(self, parent=None):