diff --git a/runtime/autoload/htmlfold.vim b/runtime/autoload/htmlfold.vim
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+" HTML folding script, :h ft-html-plugin
+" Latest Change: 2025 May 10
+" Original Author: Aliaksei Budavei <0x000c70@gmail.com>
+
+function! htmlfold#MapBalancedTags() abort
+  " Describe only _a capturable-name prefix_ for start and end patterns of
+  " a tag so that start tags with attributes spanning across lines can also be
+  " matched with a single call of "getline()".
+  let tag = '\m\c</\=\([0-9A-Za-z-]\+\)'
+  let names = []
+  let pairs = []
+  let ends = []
+  let pos = getpos('.')
+
+  try
+    call cursor(1, 1)
+    let [lnum, cnum] = searchpos(tag, 'cnW')
+
+    " Pair up nearest non-inlined tags in scope.
+    while lnum > 0
+      let name_attr = synIDattr(synID(lnum, cnum, 0), 'name')
+
+      if name_attr ==# 'htmlTag' || name_attr ==# 'htmlScriptTag'
+	let name = get(matchlist(getline(lnum), tag, (cnum - 1)), 1, '')
+
+	if !empty(name)
+	  call insert(names, tolower(name), 0)
+	  call insert(pairs, [lnum, -1], 0)
+	endif
+      elseif name_attr ==# 'htmlEndTag'
+	let name = get(matchlist(getline(lnum), tag, (cnum - 1)), 1, '')
+
+	if !empty(name)
+	  let idx = index(names, tolower(name))
+
+	  if idx >= 0
+	    " Dismiss inlined balanced tags and opened-only tags.
+	    if pairs[idx][0] != lnum
+	      let pairs[idx][1] = lnum
+	      call add(ends, lnum)
+	    endif
+
+	    " Claim a pair.
+	    let names[: idx] = repeat([''], (idx + 1))
+	  endif
+	endif
+      endif
+
+      " Advance the cursor, at "<", past "</a", "<a>", etc.
+      call cursor(lnum, (cnum + 3))
+      let [lnum, cnum] = searchpos(tag, 'cnW')
+    endwhile
+  finally
+    call setpos('.', pos)
+  endtry
+
+  if empty(ends)
+    return {}
+  endif
+
+  let folds = {}
+  let pending_end = ends[0]
+  let level = 0
+
+  while !empty(pairs)
+    let [start, end] = remove(pairs, -1)
+
+    if end < 0
+      continue
+    endif
+
+    if start >= pending_end
+      " Mark a sibling tag.
+      call remove(ends, 0)
+
+      while start >= ends[0]
+	" Mark a parent tag.
+	call remove(ends, 0)
+	let level -= 1
+      endwhile
+
+      let pending_end = ends[0]
+    else
+      " Mark a child tag.
+      let level += 1
+    endif
+
+    " Flatten the innermost inlined folds.
+    let folds[start] = get(folds, start, ('>' . level))
+    let folds[end] = get(folds, end, ('<' . level))
+  endwhile
+
+  return folds
+endfunction
+
+" See ":help vim9-mix".
+if !has("vim9script")
+  finish
+endif
+
+def! g:htmlfold#MapBalancedTags(): dict<string>
+  # Describe only _a capturable-name prefix_ for start and end patterns of
+  # a tag so that start tags with attributes spanning across lines can also be
+  # matched with a single call of "getline()".
+  const tag: string = '\m\c</\=\([0-9A-Za-z-]\+\)'
+  var names: list<string> = []
+  var pairs: list<list<number>> = []
+  var ends: list<number> = []
+  const pos: list<number> = getpos('.')
+
+  try
+    cursor(1, 1)
+    var [lnum: number, cnum: number] = searchpos(tag, 'cnW')
+
+    # Pair up nearest non-inlined tags in scope.
+    while lnum > 0
+      const name_attr: string = synIDattr(synID(lnum, cnum, 0), 'name')
+
+      if name_attr ==# 'htmlTag' || name_attr ==# 'htmlScriptTag'
+	const name: string = get(matchlist(getline(lnum), tag, (cnum - 1)), 1, '')
+
+	if !empty(name)
+	  insert(names, tolower(name), 0)
+	  insert(pairs, [lnum, -1], 0)
+	endif
+      elseif name_attr ==# 'htmlEndTag'
+	const name: string = get(matchlist(getline(lnum), tag, (cnum - 1)), 1, '')
+
+	if !empty(name)
+	  const idx: number = index(names, tolower(name))
+
+	  if idx >= 0
+	    # Dismiss inlined balanced tags and opened-only tags.
+	    if pairs[idx][0] != lnum
+	      pairs[idx][1] = lnum
+	      add(ends, lnum)
+	    endif
+
+	    # Claim a pair.
+	    names[: idx] = repeat([''], (idx + 1))
+	  endif
+	endif
+      endif
+
+      # Advance the cursor, at "<", past "</a", "<a>", etc.
+      cursor(lnum, (cnum + 3))
+      [lnum, cnum] = searchpos(tag, 'cnW')
+    endwhile
+  finally
+    setpos('.', pos)
+  endtry
+
+  if empty(ends)
+    return {}
+  endif
+
+  var folds: dict<string> = {}
+  var pending_end: number = ends[0]
+  var level: number = 0
+
+  while !empty(pairs)
+    const [start: number, end: number] = remove(pairs, -1)
+
+    if end < 0
+      continue
+    endif
+
+    if start >= pending_end
+      # Mark a sibling tag.
+      remove(ends, 0)
+
+      while start >= ends[0]
+	# Mark a parent tag.
+	remove(ends, 0)
+	level -= 1
+      endwhile
+
+      pending_end = ends[0]
+    else
+      # Mark a child tag.
+      level += 1
+    endif
+
+    # Flatten the innermost inlined folds.
+    folds[start] = get(folds, start, ('>' .. level))
+    folds[end] = get(folds, end, ('<' .. level))
+  endwhile
+
+  return folds
+enddef
+
+" vim: fdm=syntax sw=2 ts=8 noet