[parsing] search for case-insensitive tag names

test/test_parsing.py

@@ -222,6 +222,10 @@ class TestParsing(unittest.TestCase):
             get_element_text_and_html_by_tag('orphan', f'<orphan>{html}'), ('', '<orphan>'))
         self.assertIsNone(get_element_text_and_html_by_tag('orphan', f'{html}</orphan>'))
 
+        # ignore case on tags
+        ci_html = f'<SpAn>{html}</sPaN>'
+        self.assertEqual(get_element_text_and_html_by_tag('span', ci_html), (html, ci_html))
+
     def test_strict_html_parsing(self):
         class StrictTagParser(HTMLTagParser):
             STRICT = True

yt_dlp/parsing.py

@@ -245,7 +245,7 @@ class MatchingElementParser(HTMLTagParser):
             value_regex = re.escape(value_regex)
 
         return rf'''(?x)
-            <(?:{tag})
+            <(?i:{tag})
              (?:\s(?:[^>"'\\]|"[^"\\]*"|'[^'\\]*')*)?
              \s{re.escape(attribute)}\s*=\s*(?P<_q>['"])(?-x:{value_regex})(?P=_q)
             '''
@@ -263,7 +263,7 @@ class MatchingElementParser(HTMLTagParser):
         def matchfunc(tag_str, _attrs):
             return tag_str == tag
 
-        tag_regex = rf'''<\s*{re.escape(tag)}(?:\s(?:[^>"'\\]|"[^"\\]*"|'[^'\\]*')*)?>'''
+        tag_regex = rf'''<\s*(?i:{re.escape(tag)})(?:\s(?:[^>"'\\]|"[^"\\]*"|'[^'\\]*')*)?>'''
         yield from cls.iter_tags(tag_regex, html, matchfunc=matchfunc)
 
     @classmethod