diff --git a/emcc.py b/emcc.py
index b54b380e5d39a..c91d238b76b65 100644
--- a/emcc.py
+++ b/emcc.py
@@ -173,7 +173,7 @@
     '--bind', '--closure', '--cpuprofiler', '--embed-file',
     '--emit-symbol-map', '--emrun', '--exclude-file', '--extern-post-js',
     '--extern-pre-js', '--ignore-dynamic-linking', '--js-library',
-    '--js-transform', '--memory-init-file', '--oformat', '--output_eol',
+    '--js-transform', '--memory-init-file', '--oformat', '--output_eol', '--output-eol',
     '--post-js', '--pre-js', '--preload-file', '--profiling-funcs',
     '--proxy-to-worker', '--shell-file', '--source-map-base',
     '--threadprofiler', '--use-preload-plugins'
@@ -3427,8 +3427,7 @@ def phase_final_emitting(options, state, target, wasm_target, memfile):
     diagnostics.warning('experimental', 'The SPLIT_MODULE setting is experimental and subject to change')
     do_split_module(wasm_target, options)
 
-  if not settings.SINGLE_FILE:
-    tools.line_endings.convert_line_endings_in_file(js_target, os.linesep, options.output_eol)
+  tools.line_endings.convert_line_endings_in_file(js_target, options.output_eol)
 
   if options.executable:
     make_js_executable(js_target)
@@ -3731,14 +3730,14 @@ def consume_arg_file():
         options.default_object_extension = '.' + options.default_object_extension
     elif arg.startswith('-fsanitize=cfi'):
       exit_with_error('emscripten does not currently support -fsanitize=cfi')
-    elif check_arg('--output_eol'):
+    elif check_arg('--output_eol') or check_arg('--output-eol'):
       style = consume_arg()
       if style.lower() == 'windows':
         options.output_eol = '\r\n'
       elif style.lower() == 'linux':
         options.output_eol = '\n'
       else:
-        exit_with_error(f'Invalid value "{style}" to --output_eol!')
+        exit_with_error(f'invalid value for --output-eol: `{style}`')
     # Record PTHREADS setting because it controls whether --shared-memory is passed to lld
     elif arg == '-pthread':
       settings.PTHREADS = 1
@@ -4198,12 +4197,7 @@ def generate_traditional_runtime_html(target, options, js_target, target_basenam
 
   html_contents = do_replace(shell, '{{{ SCRIPT }}}', script.replacement())
   html_contents = tools.line_endings.convert_line_endings(html_contents, '\n', options.output_eol)
-
-  try:
-    # Force UTF-8 output for consistency across platforms and with the web.
-    utils.write_binary(target, html_contents.encode('utf-8'))
-  except OSError as e:
-    exit_with_error(f'cannot write output file: {e}')
+  utils.write_file(target, html_contents)
 
 
 def minify_html(filename):
diff --git a/tools/line_endings.py b/tools/line_endings.py
index 2e1f1b3b95eda..43bdaf9d05071 100755
--- a/tools/line_endings.py
+++ b/tools/line_endings.py
@@ -7,6 +7,8 @@
 import os
 import sys
 
+from . import utils
+
 
 def convert_line_endings(text, from_eol, to_eol):
   if from_eol == to_eol:
@@ -14,15 +16,13 @@ def convert_line_endings(text, from_eol, to_eol):
   return text.replace(from_eol, to_eol)
 
 
-def convert_line_endings_in_file(filename, from_eol, to_eol):
-  if from_eol == to_eol:
+def convert_line_endings_in_file(filename, to_eol):
+  if to_eol == os.linesep:
     return # No conversion needed
 
-  with open(filename, 'rb') as f:
-    text = f.read()
-  text = convert_line_endings(text, from_eol.encode(), to_eol.encode())
-  with open(filename, 'wb') as f:
-    f.write(text)
+  text = utils.read_binary(filename)
+  text = convert_line_endings(text, os.linesep.encode(), to_eol.encode())
+  utils.write_binary(filename, text)
 
 
 def check_line_endings(filename, expect_only=None, print_errors=True, print_info=False):