diff --git a/src/calibre/ebooks/html/to_zip.py b/src/calibre/ebooks/html/to_zip.py
index 30e3023e77..2233ea57a7 100644
--- a/src/calibre/ebooks/html/to_zip.py
+++ b/src/calibre/ebooks/html/to_zip.py
@@ -24,6 +24,20 @@ every time you add an HTML file to the library.\
     supported_platforms = ['windows', 'osx', 'linux']
     on_import = True
 
+    def parse_my_settings(self, sc):
+        if not sc:
+            sc = ''
+        if sc.startswith('{'):
+            import json
+            try:
+                return json.loads(sc)
+            except Exception:
+                return {}
+        else:
+            sc = sc.strip()
+            enc, _, bfs = sc.partition('|')
+            return {'encoding': enc, 'breadth_first': bfs == 'bf'}
+
     def run(self, htmlfile):
         import codecs
         from calibre import prints
@@ -36,8 +50,8 @@ every time you add an HTML file to the library.\
             recs =[('debug_pipeline', tdir, OptionRecommendation.HIGH)]
             recs.append(['keep_ligatures', True, OptionRecommendation.HIGH])
             if self.site_customization and self.site_customization.strip():
-                sc = self.site_customization.strip()
-                enc, _, bf = sc.partition('|')
+                settings = self.parse_my_settings(self.site_customization)
+                enc = settings.get('encoding')
                 if enc:
                     try:
                         codecs.lookup(enc)
@@ -45,9 +59,8 @@ every time you add an HTML file to the library.\
                         prints('Ignoring invalid input encoding for HTML:', enc)
                     else:
                         recs.append(['input_encoding', enc, OptionRecommendation.HIGH])
-                if bf == 'bf':
-                    recs.append(['breadth_first', True,
-                        OptionRecommendation.HIGH])
+                if settings.get('breadth_first'):
+                    recs.append(['breadth_first', True, OptionRecommendation.HIGH])
             gui_convert(htmlfile, tdir, recs, abort_after_input_dump=True)
             of = self.temporary_file('_plugin_html2zip.zip')
             tdir = os.path.join(tdir, 'input')
@@ -63,7 +76,7 @@ every time you add an HTML file to the library.\
 
     def customization_help(self, gui=False):
         return _('Character encoding for the input HTML files. Common choices '
-        'include: cp1252, cp1251, latin1 and utf-8.')
+        'include: utf-8, cp1252, cp1251 and latin1.')
 
     def do_user_config(self, parent=None):
         '''
@@ -71,6 +84,7 @@ every time you add an HTML file to the library.\
         True if the user clicks OK, False otherwise. The changes are
         automatically applied.
         '''
+        import json
         from qt.core import (QDialog, QDialogButtonBox, QVBoxLayout,
                 QLabel, Qt, QLineEdit, QCheckBox)
 
@@ -97,14 +111,9 @@ every time you add an HTML file to the library.\
             ' calibre does it depth first, i.e. if file A links to B and '
             ' C, but B links to D, the files are added in the order A, B, D, C. '
             ' With this option, they will instead be added as A, B, C, D'))
-        sc = plugin_customization(self)
-        if not sc:
-            sc = ''
-        sc = sc.strip()
-        enc = sc.partition('|')[0]
-        bfs = sc.partition('|')[-1]
-        bf.setChecked(bfs == 'bf')
-        sc = QLineEdit(enc, config_dialog)
+        settings = self.parse_my_settings(plugin_customization(self))
+        bf.setChecked(bool(settings.get('breadth_first')))
+        sc = QLineEdit(str(settings.get('encoding', '')), config_dialog)
         v.addWidget(sc)
         v.addWidget(bf)
         v.addWidget(button_box)
@@ -112,9 +121,12 @@ every time you add an HTML file to the library.\
         config_dialog.exec()
 
         if config_dialog.result() == QDialog.DialogCode.Accepted:
-            sc = str(sc.text()).strip()
+            settings = {}
+            enc = str(sc.text()).strip()
+            if enc:
+                settings['encoding'] = enc
             if bf.isChecked():
-                sc += '|bf'
-            customize_plugin(self, sc)
+                settings['breadth_first'] = True
+            customize_plugin(self, json.dumps(settings, ensure_ascii=True))
 
         return config_dialog.result()