diff --git a/HISTORY.md b/HISTORY.md
index 4e0dc5c..68c1512 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -1,21 +1,27 @@
 # Changelog
 
-## 4.0.1 (unreleased)
+## 4.1.0 (unreleased)
 
+- Add a switch for multiline class attribute values.
+  Per default class attributes are not split into multiple lines. That's what
+  most tools do and most people would expect. To split class attributes into
+  multiple lines use the `--split-class` option on the CLI.
+  [thet]
 
-- Nothing changed yet.
-
+- Multiline values for class attributes.
+  Split multiple class attribute values into multiple lines. Keep it
+  single-lined, if there is only one value. And don't split Chameleon
+  expressions.
+  [thet]
 
 ## 4.0.0 (2026-04-10)
 
-
 - Declare support for Python 3.10 - 3.14
   [ale-rt]
 - Do not break `title` and `textarea` in page templates.
   (Fixes #198)
   [ale-rt]
 
-
 ## 3.1.1 (2025-06-23)
 
 - When parsing XML files, preserve space in all the tags
@@ -24,10 +30,8 @@
 - Declare support for Python 3.13
   [ale-rt]
 
-
 ## 3.1.0 (2023-06-30)
 
-
 - No changes were made from the latest alpha version
   [ale-rt]
 
diff --git a/README.md b/README.md
index 86f514f..d75c1b9 100644
--- a/README.md
+++ b/README.md
@@ -69,8 +69,8 @@ Basic usage:
 
 ```console
 $ zpretty -h
-usage: zpretty [-h] [--encoding ENCODING] [-i] [-v] [-x] [-z] [--check]
-               [--include INCLUDE] [--exclude EXCLUDE]
+usage: zpretty [-h] [--encoding ENCODING] [-i] [-v] [-x] [-z] [--split-class]
+               [--check] [--include INCLUDE] [--exclude EXCLUDE]
                [--extend-exclude EXTEND_EXCLUDE]
                [paths ...]
 
@@ -88,6 +88,7 @@ options:
   -x, --xml             Treat the input file(s) as XML
   -z, --zcml            Treat the input file(s) as XML. Follow the ZCML
                         styleguide
+  --split-class         Split CSS class attribute values into multiple lines.
   --check               Return code 0 if nothing would be changed, 1 if some
                         files would be reformatted
   --include INCLUDE     A regular expression that matches files and directories
diff --git a/zpretty/attributes.py b/zpretty/attributes.py
index 05ec795..a8fbbe0 100644
--- a/zpretty/attributes.py
+++ b/zpretty/attributes.py
@@ -78,11 +78,15 @@ class PrettyAttributes:
         "i18n:ignore-attributes",
     )
 
-    def __init__(self, attributes, element=None):
+    def __init__(self, config, attributes, element=None):
         """attributes is a dict like object"""
+        self.config = config
         self.attributes = attributes
         self.element = element
 
+        if self.config.split_class:
+            self._multiline_attributes += ("class",)
+
     def __len__(self):
         return len(self.attributes)
 
@@ -129,11 +133,60 @@ def sort_attributes(self, name):
             return (900, name)
         return (200, name)
 
+    def split_outside_braces(self, value: str) -> list[str]:
+        """Empty space splitter that respects Chameleon expressions.
+
+        It splits on ` ` except for expressions within `{}`
+        """
+        parts = []
+        current = []
+        depth = 0
+
+        for char in value:
+            if char == "{":
+                depth += 1
+                current.append(char)
+            elif char == "}":
+                depth -= 1
+                current.append(char)
+            elif char == " " and depth == 0:
+                if current:
+                    parts.append("".join(current))
+                    current = []
+            else:
+                current.append(char)
+
+        if current:
+            parts.append("".join(current))
+
+        return parts
+
     def format_multiline(self, name, value):
-        """"""
-        value_lines = filter(None, value.split())
-        line_joiner = "\n" + (" " * (len(name) + 2))
-        return line_joiner.join(value_lines)
+        """Format attributes values to multiline, split on an empty space.` `
+        except for expressions within `{}`
+        """
+
+        lines = self.split_outside_braces(value)
+
+        # Don't split single-values
+        if len(lines) < 2:
+            return value
+
+        try:
+            line_prefix = self.element.prefix + self.prefix + self._multiline_prefix
+        except AttributeError:
+            line_prefix = self._multiline_prefix
+
+        # unindent at the end
+        line_prefix_end = line_prefix[:-2]
+
+        # Add line indents
+        new_value = line_prefix + f"\n{line_prefix}".join(lines)
+
+        # Line break at start and end and add end indent.
+        new_value = f"\n{new_value}\n{line_prefix_end}"
+
+        return new_value
 
     def format_tal_multiline(self, value):
         """There are some tal specific attributes that contain ; separated
diff --git a/zpretty/cli.py b/zpretty/cli.py
index e11369f..cb8b75f 100644
--- a/zpretty/cli.py
+++ b/zpretty/cli.py
@@ -72,6 +72,13 @@ def parser(self):
             dest="zcml",
             default=False,
         )
+        parser.add_argument(
+            "--split-class",
+            help="Split CSS class attribute values into multiple lines.",
+            action="store_true",
+            dest="split_class",
+            default=False,
+        )
         parser.add_argument(
             "--check",
             help=(
@@ -212,7 +219,7 @@ def run(self):
         for path in self.good_paths:
             # use Pathlib to check if the file exists and it is a file
             Prettifier = self.choose_prettifier(path)
-            prettifier = Prettifier(path, encoding=encoding)
+            prettifier = Prettifier(self.config, path, encoding=encoding)
             if self.config.check:
                 if not prettifier.check():
                     self.errors.append(f"This file would be rewritten: {path}")
diff --git a/zpretty/elements.py b/zpretty/elements.py
index 5eb2053..d3740f0 100644
--- a/zpretty/elements.py
+++ b/zpretty/elements.py
@@ -91,8 +91,9 @@ class PrettyElement:
         "textarea",
     ]
 
-    def __init__(self, context, level=0):
+    def __init__(self, config, context, level=0):
         """Take something a (bs4) element and an indentation level"""
+        self.config = config
         self.context = context
         self.level = level
 
@@ -180,7 +181,7 @@ def getparent(self):
         parent = self.context.parent
         if not parent or parent.name == BeautifulSoup.ROOT_TAG_NAME:
             return None
-        return self.__class__(parent)
+        return self.__class__(self.config, parent)
 
     @memo
     def getchildren(self):
@@ -188,7 +189,7 @@ def getchildren(self):
         children = []
         next_level = self.level + 1
         for child in getattr(self.context, "children", []):
-            child = self.__class__(child, next_level)
+            child = self.__class__(self.config, child, next_level)
             try:
                 child.is_tag() and child.is_self_closing()
             except OpenTagException:
@@ -227,7 +228,7 @@ def text(self):
     def attributes(self):
         """Return the wrapped attributes"""
         attributes = getattr(self.context, "attrs", {})
-        return self.attribute_klass(attributes, self)
+        return self.attribute_klass(self.config, attributes, self)
 
     @property
     @memo
diff --git a/zpretty/prettifier.py b/zpretty/prettifier.py
index 097d89d..9da2186 100644
--- a/zpretty/prettifier.py
+++ b/zpretty/prettifier.py
@@ -31,10 +31,11 @@ class ZPrettifier:
     _cdatas = []
     _doctype = None
 
-    def __init__(self, filename="", text="", encoding="utf8"):
+    def __init__(self, config, filename="", text="", encoding="utf8"):
         """Create a prettifier instance taking the contents
         from a text or a filename
         """
+        self.config = config
         self._entity_mapping = {}
         self.encoding = encoding
         self.filename = filename
@@ -67,7 +68,7 @@ def __init__(self, filename="", text="", encoding="utf8"):
         for el in self.soup.find_all(attrs={key: ""}):
             el.attrs.pop(key, None)
 
-        self.root = self.pretty_element(self.soup, -1)
+        self.root = self.pretty_element(config, self.soup, -1)
 
     def fix_rcdata_markup(self, soup):
         """Parse markup-like text inside RCDATA tags as child nodes.
diff --git a/zpretty/tests/test_attributes.py b/zpretty/tests/test_attributes.py
index bcc40a4..e332d74 100644
--- a/zpretty/tests/test_attributes.py
+++ b/zpretty/tests/test_attributes.py
@@ -4,6 +4,10 @@
 from zpretty.elements import PrettyElement
 
 
+class FakeConfig:
+    split_class = False
+
+
 class TestZPrettyAttributess(TestCase):
     """Test zpretty"""
 
@@ -12,15 +16,18 @@ def get_element(self, text, level=0):
         soup = BeautifulSoup(
             "<soup><fake_root>%s</fake_root></soup>" % text, "html.parser"
         )
-        return PrettyElement(soup.fake_root.next_element, level)
+        return PrettyElement(FakeConfig(), soup.fake_root.next_element, level)
 
-    def assertPrettifiedAttributes(self, attributes, expected, level=0):
+    def assertPrettifiedAttributes(self, attributes, expected, level=0, config=None):
         """Check if the attributes are properly sorted and formatted"""
         if level == 0:
             el = None
         else:
             el = self.get_element("a", level)
-        pretty_attribute = PrettyAttributes(attributes, el)
+
+        config = config if config else FakeConfig()
+
+        pretty_attribute = PrettyAttributes(config, attributes, el)
         observed = pretty_attribute()
         self.assertEqual(observed, expected)
 
@@ -77,3 +84,44 @@ def test_format_attributes_many_attribute(self):
                 )
             ),
         )
+
+    def test_class_multiline_no_split(self):
+        """Class attributes with multiple values should be split."""
+        self.assertPrettifiedAttributes(
+            {"class": "class1 class2 ${python: 'class3' if True else ''} class4"},
+            '''class="class1 class2 ${python: 'class3' if True else ''} class4"''',
+        )
+
+    def test_class_multiline(self):
+        """Class attributes with multiple values should be split."""
+        config = FakeConfig()
+        config.split_class = True
+        self.assertPrettifiedAttributes(
+            {"class": "class1 class2 ${python: 'class3' if True else ''} class4"},
+            "\n".join(
+                (
+                    'class="',
+                    "  class1",
+                    "  class2",
+                    "  ${python: 'class3' if True else ''}",
+                    "  class4",
+                    '"',
+                )
+            ),
+            0,
+            config,
+        )
+
+    def test_data_pat_singleline(self):
+        """Class with single values should not be split."""
+        config = FakeConfig()
+        config.split_class = True
+        self.assertPrettifiedAttributes(
+            {"class": "class1"}, 'class="class1"', 0, config
+        )
+
+    def test_data_pat_empty(self):
+        """Empty class attributes should not be split."""
+        config = FakeConfig()
+        config.split_class = True
+        self.assertPrettifiedAttributes({"class": ""}, 'class=""', 0, config)
diff --git a/zpretty/tests/test_elements.py b/zpretty/tests/test_elements.py
index 9df6dbd..59e31cc 100644
--- a/zpretty/tests/test_elements.py
+++ b/zpretty/tests/test_elements.py
@@ -3,6 +3,10 @@
 from zpretty.elements import PrettyElement
 
 
+class FakeConfig:
+    split_class = False
+
+
 class TestPrettyElements(TestCase):
     """Test basic funtionalities of the PrettyElement class"""
 
@@ -11,7 +15,7 @@ def get_element(self, text, level=0):
         soup = BeautifulSoup(
             "<soup><fake_root>%s</fake_root></soup>" % text, "html.parser"
         )
-        return PrettyElement(soup.fake_root.next_element, level)
+        return PrettyElement(FakeConfig(), soup.fake_root.next_element, level)
 
     def test_comment(self):
         el = self.get_element("<!--a-->")
diff --git a/zpretty/tests/test_xml.py b/zpretty/tests/test_xml.py
index c66efe5..e44a8a1 100644
--- a/zpretty/tests/test_xml.py
+++ b/zpretty/tests/test_xml.py
@@ -5,6 +5,10 @@
 from zpretty.xml import XMLPrettifier
 
 
+class FakeConfig:
+    split_class = False
+
+
 class TestZpretty(TestCase):
     """Test zpretty"""
 
@@ -17,14 +21,14 @@ def get_element(self, text, level=0):
         soup = BeautifulSoup(
             "<soup><fake_root>%s</fake_root></soup>" % text, "html.parser"
         )
-        return XMLElement(soup.fake_root.next_element, level)
+        return XMLElement(FakeConfig(), soup.fake_root.next_element, level)
 
     def prettify(self, filename):
         """Run prettify on filename and check that the output is equal to
         the file content itself
         """
         filename_path = self.sample_folder_path / filename
-        prettifier = XMLPrettifier(filename_path)
+        prettifier = XMLPrettifier(FakeConfig(), filename_path)
         observed = prettifier()
         expected = filename_path.read_text()
         self.assertListEqual(observed.splitlines(), expected.splitlines())
diff --git a/zpretty/tests/test_zcml.py b/zpretty/tests/test_zcml.py
index d5ccb7b..3cfb8ed 100644
--- a/zpretty/tests/test_zcml.py
+++ b/zpretty/tests/test_zcml.py
@@ -6,6 +6,10 @@
 from zpretty.zcml import ZCMLPrettifier
 
 
+class FakeConfig:
+    split_class = False
+
+
 class TestZpretty(TestCase):
     """Test zpretty"""
 
@@ -17,7 +21,7 @@ def get_element(self, text, level=0):
         soup = BeautifulSoup(
             "<soup><fake_root>%s</fake_root></soup>" % text, "html.parser"
         )
-        return ZCMLElement(soup.fake_root.next_element, level)
+        return ZCMLElement(FakeConfig(), soup.fake_root.next_element, level)
 
     def assertPrettifiedAttributes(self, attributes, expected, level=0):
         """Check if the attributes are properly sorted and formatted"""
@@ -25,12 +29,12 @@ def assertPrettifiedAttributes(self, attributes, expected, level=0):
             el = None
         else:
             el = self.get_element("foo", level)
-        pretty_attribute = ZCMLAttributes(attributes, el)
+        pretty_attribute = ZCMLAttributes(FakeConfig(), attributes, el)
         observed = pretty_attribute()
         self.assertEqual(observed, expected)
 
     def test_zcml_attributes_no_attributes(self):
-        self.assertPrettifiedAttributes(ZCMLAttributes({})(), "")
+        self.assertPrettifiedAttributes(ZCMLAttributes(FakeConfig(), {})(), "")
         self.assertPrettifiedAttributes({}, "", level=2)
 
     def test_zcml_attributes_one_attributes(self):
@@ -225,7 +229,7 @@ def prettify(self, filename):
         the file content itself
         """
         filename_path = self.sample_folder_path / filename
-        prettifier = ZCMLPrettifier(filename_path)
+        prettifier = ZCMLPrettifier(FakeConfig(), filename_path)
         observed = prettifier()
         expected = filename_path.read_text()
         self.assertListEqual(observed.splitlines(), expected.splitlines())
diff --git a/zpretty/tests/test_zpretty.py b/zpretty/tests/test_zpretty.py
index af66060..cb11b62 100644
--- a/zpretty/tests/test_zpretty.py
+++ b/zpretty/tests/test_zpretty.py
@@ -3,6 +3,10 @@
 from zpretty.prettifier import ZPrettifier
 
 
+class FakeConfig:
+    split_class = False
+
+
 class TestZpretty(TestCase):
     """Test zpretty"""
 
@@ -13,7 +17,7 @@ def assertPrettified(self, original, expected, encoding="utf8"):
         """Check if the original html has been prettified as expected"""
         if isinstance(expected, tuple):
             expected = "\n".join(expected)
-        prettifier = ZPrettifier(text=original, encoding=encoding)
+        prettifier = ZPrettifier(FakeConfig(), text=original, encoding=encoding)
         self.assertFalse(prettifier.check())
         observed = prettifier()
         self.assertEqual(observed, expected)
@@ -23,7 +27,7 @@ def prettify(self, filename):
         the file content itself
         """
         filename_path = self.sample_folder_path / filename
-        prettifier = ZPrettifier(filename_path)
+        prettifier = ZPrettifier(FakeConfig(), filename_path)
         self.assertTrue(prettifier.check())
         observed = prettifier()
         expected = filename_path.read_text()
@@ -153,7 +157,7 @@ def test_textarea_prettifies_markup_like_text(self):
         )
 
     def test_element_repr(self):
-        prettifier = ZPrettifier(text="")
+        prettifier = ZPrettifier(FakeConfig(), text="")
         self.assertEqual(repr(prettifier.root), "<pretty:-1:null_tag_name />")
 
     def test_whitelines_not_stripped(self):