diff --git a/embuilder.py b/embuilder.py
index 917a0361c123..3c770a7d05e9 100755
--- a/embuilder.py
+++ b/embuilder.py
@@ -23,6 +23,7 @@
 from tools import shared
 from tools import system_libs
 from tools import ports
+from tools import utils
 from tools.settings import settings
 from tools.system_libs import USE_NINJA
 
@@ -169,6 +170,10 @@ def get_all_tasks():
   return get_system_tasks()[1] + PORTS
 
 
+def handle_port_error(target, message):
+  utils.exit_with_error(f'error building port `{target}` | {message}')
+
+
 def main():
   all_build_start_time = time.time()
 
@@ -289,6 +294,12 @@ def main():
         clear_port(what)
       if do_build:
         build_port(what)
+    elif ':' in what or what.endswith('.py'):
+      name = ports.handle_use_port_arg(settings, what, lambda message: handle_port_error(what, message))
+      if do_clear:
+        clear_port(name)
+      if do_build:
+        build_port(name)
     else:
       logger.error('unfamiliar build target: ' + what)
       return 1
diff --git a/test/other/ports/external.py b/test/other/ports/external.py
index 0ca8eabc8b0f..3df5adb6c190 100644
--- a/test/other/ports/external.py
+++ b/test/other/ports/external.py
@@ -23,7 +23,10 @@
 
 
 def get_lib_name(settings):
-  return 'lib_external.a'
+  if opts['dependency']:
+    return f'lib_external-{opts["dependency"]}.a'
+  else:
+    return 'lib_external.a'
 
 
 def get(ports, settings, shared):
@@ -58,5 +61,5 @@ def process_dependencies(settings):
     deps.append(opts['dependency'])
 
 
-def handle_options(options):
+def handle_options(options, error_handler):
   opts.update(options)
diff --git a/test/test_other.py b/test/test_other.py
index 7a8f24abecab..7c0759dc7c9e 100644
--- a/test/test_other.py
+++ b/test/test_other.py
@@ -2416,7 +2416,7 @@ def test_external_ports(self):
     # testing invalid dependency
     stderr = self.expect_fail([EMCC, test_file('other/test_external_ports.c'), f'--use-port={external_port_path}:dependency=invalid', '-o', 'a4.out.js'])
     self.assertFalse(os.path.exists('a4.out.js'))
-    self.assertContained('Unknown dependency `invalid` for port `external`', stderr)
+    self.assertContained('unknown dependency `invalid` for port `external`', stderr)
 
   def test_link_memcpy(self):
     # memcpy can show up *after* optimizations, so after our opportunity to link in libc, so it must be special-cased
@@ -14557,16 +14557,16 @@ def test_js_preprocess_pre_post(self):
   def test_use_port_errors(self, compiler):
     stderr = self.expect_fail([compiler, test_file('hello_world.c'), '--use-port=invalid', '-o', 'out.js'])
     self.assertFalse(os.path.exists('out.js'))
-    self.assertContained('Error with `--use-port=invalid` | invalid port name: `invalid`', stderr)
+    self.assertContained('error with `--use-port=invalid` | invalid port name: `invalid`', stderr)
     stderr = self.expect_fail([compiler, test_file('hello_world.c'), '--use-port=sdl2:opt1=v1', '-o', 'out.js'])
     self.assertFalse(os.path.exists('out.js'))
-    self.assertContained('Error with `--use-port=sdl2:opt1=v1` | no options available for port `sdl2`', stderr)
+    self.assertContained('error with `--use-port=sdl2:opt1=v1` | no options available for port `sdl2`', stderr)
     stderr = self.expect_fail([compiler, test_file('hello_world.c'), '--use-port=sdl2_image:format=jpg', '-o', 'out.js'])
     self.assertFalse(os.path.exists('out.js'))
-    self.assertContained('Error with `--use-port=sdl2_image:format=jpg` | `format` is not supported', stderr)
+    self.assertContained('error with `--use-port=sdl2_image:format=jpg` | `format` is not supported', stderr)
     stderr = self.expect_fail([compiler, test_file('hello_world.c'), '--use-port=sdl2_image:formats', '-o', 'out.js'])
     self.assertFalse(os.path.exists('out.js'))
-    self.assertContained('Error with `--use-port=sdl2_image:formats` | `formats` is missing a value', stderr)
+    self.assertContained('error with `--use-port=sdl2_image:formats` | `formats` is missing a value', stderr)
     stderr = self.expect_fail([compiler, test_file('hello_world.c'), '--use-port=sdl2_image:formats=jpg:formats=png', '-o', 'out.js'])
     self.assertFalse(os.path.exists('out.js'))
-    self.assertContained('Error with `--use-port=sdl2_image:formats=jpg:formats=png` | duplicate option `formats`', stderr)
+    self.assertContained('error with `--use-port=sdl2_image:formats=jpg:formats=png` | duplicate option `formats`', stderr)
diff --git a/test/test_sanity.py b/test/test_sanity.py
index 0375e28237a9..e1de89dd1271 100644
--- a/test/test_sanity.py
+++ b/test/test_sanity.py
@@ -748,6 +748,28 @@ def test_embuilder_wildcards(self):
     self.run_process([EMBUILDER, 'build', 'libwebgpu*'])
     self.assertGreater(len(glob.glob(glob_match)), 3)
 
+  def test_embuilder_with_use_port_syntax(self):
+    restore_and_set_up()
+    self.run_process([EMBUILDER, 'build', 'sdl2_image:formats=png,jpg', '--force'])
+    self.assertExists(os.path.join(config.CACHE, 'sysroot', 'lib', 'wasm32-emscripten', 'libSDL2_image_jpg-png.a'))
+    self.assertContained('error building port `sdl2_image:formats=invalid` | invalid is not a supported format', self.do([EMBUILDER, 'build', 'sdl2_image:formats=invalid', '--force']))
+
+  def test_embuilder_external_ports(self):
+    restore_and_set_up()
+    simple_port_path = test_file("other/ports/simple.py")
+    # embuilder handles external port target that ends with .py
+    self.run_process([EMBUILDER, 'build', f'{simple_port_path}', '--force'])
+    self.assertExists(os.path.join(config.CACHE, 'sysroot', 'lib', 'wasm32-emscripten', 'lib_simple.a'))
+    # embuilder handles external port target that contains port options
+    external_port_path = test_file("other/ports/external.py")
+    self.run_process([EMBUILDER, 'build', f'{external_port_path}:value1=12:value2=36', '--force'])
+    self.assertExists(os.path.join(config.CACHE, 'sysroot', 'lib', 'wasm32-emscripten', 'lib_external.a'))
+    # embuilder handles external port target that contains port options (influences library name,
+    # like sdl2_image:formats=png)
+    external_port_path = test_file("other/ports/external.py")
+    self.run_process([EMBUILDER, 'build', f'{external_port_path}:dependency=sdl2', '--force'])
+    self.assertExists(os.path.join(config.CACHE, 'sysroot', 'lib', 'wasm32-emscripten', 'lib_external-sdl2.a'))
+
   def test_binaryen_version(self):
     restore_and_set_up()
     with open(EM_CONFIG, 'a') as f:
diff --git a/tools/ports/__init__.py b/tools/ports/__init__.py
index 18ce4dd995f2..2241991ece9f 100644
--- a/tools/ports/__init__.py
+++ b/tools/ports/__init__.py
@@ -398,7 +398,7 @@ def add_deps(node):
     node.process_dependencies(settings)
     for d in node.deps:
       if d not in ports_by_name:
-        utils.exit_with_error(f'Unknown dependency `{d}` for port `{node.name}`')
+        utils.exit_with_error(f'unknown dependency `{d}` for port `{node.name}`')
       dep = ports_by_name[d]
       if dep not in port_set:
         port_set.add(dep)
@@ -409,10 +409,13 @@ def add_deps(node):
 
 
 def handle_use_port_error(arg, message):
-  utils.exit_with_error(f'Error with `--use-port={arg}` | {message}')
+  utils.exit_with_error(f'error with `--use-port={arg}` | {message}')
 
 
-def handle_use_port_arg(settings, arg):
+def handle_use_port_arg(settings, arg, error_handler=None):
+  if not error_handler:
+    def error_handler(message):
+      handle_use_port_error(arg, message)
   # Ignore ':' in first or second char of string since we could be dealing with a windows drive separator
   pos = arg.find(':', 2)
   if pos != -1:
@@ -422,27 +425,28 @@ def handle_use_port_arg(settings, arg):
   if name.endswith('.py'):
     port_file_path = name
     if not os.path.isfile(port_file_path):
-      handle_use_port_error(arg, f'not a valid port path: {port_file_path}')
+      error_handler(f'not a valid port path: {port_file_path}')
     name = load_port_by_path(port_file_path)
   elif name not in ports_by_name:
-    handle_use_port_error(arg, f'invalid port name: `{name}`')
+    error_handler(f'invalid port name: `{name}`')
   ports_needed.add(name)
   if options:
     port = ports_by_name[name]
     if not hasattr(port, 'handle_options'):
-      handle_use_port_error(arg, f'no options available for port `{name}`')
+      error_handler(f'no options available for port `{name}`')
     else:
       options_dict = {}
       for name_value in options.split(':'):
         nv = name_value.split('=', 1)
         if len(nv) != 2:
-          handle_use_port_error(arg, f'`{name_value}` is missing a value')
+          error_handler(f'`{name_value}` is missing a value')
         if nv[0] not in port.OPTIONS:
-          handle_use_port_error(arg, f'`{nv[0]}` is not supported; available options are {port.OPTIONS}')
+          error_handler(f'`{nv[0]}` is not supported; available options are {port.OPTIONS}')
         if nv[0] in options_dict:
-          handle_use_port_error(arg, f'duplicate option `{nv[0]}`')
+          error_handler(f'duplicate option `{nv[0]}`')
         options_dict[nv[0]] = nv[1]
-      port.handle_options(options_dict)
+      port.handle_options(options_dict, error_handler)
+  return name
 
 
 def get_needed_ports(settings):
diff --git a/tools/ports/contrib/README.md b/tools/ports/contrib/README.md
index 670b53cbd90a..42fa65edc10d 100644
--- a/tools/ports/contrib/README.md
+++ b/tools/ports/contrib/README.md
@@ -23,9 +23,10 @@ additional components:
 
 1. A handler function defined this way:
 ```python
-def handle_options(options):
+def handle_options(options, error_handler):
   # options is of type Dict[str, str]
-  # in case of error, use utils.exit_with_error('error message')
+  # in case of error, use error_handler('error message')
+  # note that error_handler is guaranteed to never return
 ```
 2. A dictionary called `OPTIONS` (type `Dict[str, str]`) where each key is the 
    name of the option and the value is a short description of what it does 
@@ -33,7 +34,7 @@ def handle_options(options):
 When emscripten detects that options have been provided, it parses them and
 check that they are valid option names for this port (using `OPTIONS`). It then
 calls the handler function with these (valid) options. If you detect an error
-with a value, you should use `tools.utils.exit_with_error` to report the 
+with a value, you should use the error handler provided to report the 
 failure.
 
 > ### Note
diff --git a/tools/ports/contrib/glfw3.py b/tools/ports/contrib/glfw3.py
index 7e83fdd30128..fe46d695e75e 100644
--- a/tools/ports/contrib/glfw3.py
+++ b/tools/ports/contrib/glfw3.py
@@ -4,7 +4,6 @@
 # found in the LICENSE file.
 
 import os
-from tools import utils
 from typing import Dict
 
 TAG = '1.0.4'
@@ -83,9 +82,9 @@ def process_args(ports):
   return ['-isystem', ports.get_include_dir('contrib.glfw3')]
 
 
-def handle_options(options):
+def handle_options(options, error_handler):
   for option, value in options.items():
     if value.lower() in {'true', 'false'}:
       opts[option] = value.lower() == 'true'
     else:
-      utils.exit_with_error(f'{option} is expecting a boolean, got {value}')
+      error_handler(f'{option} is expecting a boolean, got {value}')
diff --git a/tools/ports/sdl2_image.py b/tools/ports/sdl2_image.py
index 0adf74a0e566..2addb21b4d02 100644
--- a/tools/ports/sdl2_image.py
+++ b/tools/ports/sdl2_image.py
@@ -19,6 +19,9 @@
   'formats': 'A comma separated list of formats (ex: --use-port=sdl2_image:formats=png,jpg)'
 }
 
+SUPPORTED_FORMATS = {'avif', 'bmp', 'gif', 'jpg', 'jxl', 'lbm', 'pcx', 'png',
+                     'pnm', 'qoi', 'svg', 'tga', 'tif', 'webp', 'xcf', 'xpm', 'xv'}
+
 # user options (from --use-port)
 opts: Dict[str, Set] = {
   'formats': set()
@@ -88,8 +91,14 @@ def process_dependencies(settings):
     settings.USE_LIBJPEG = 1
 
 
-def handle_options(options):
-  opts['formats'].update({format.lower().strip() for format in options['formats'].split(',')})
+def handle_options(options, error_handler):
+  formats = options['formats'].split(',')
+  for format in formats:
+    format = format.lower().strip()
+    if format not in SUPPORTED_FORMATS:
+      error_handler(f'{format} is not a supported format')
+    else:
+      opts['formats'].add(format)
 
 
 def show():