diff --git a/eel/__init__.py b/eel/__init__.py
index 9138b1ca..c5350974 100644
--- a/eel/__init__.py
+++ b/eel/__init__.py
@@ -6,6 +6,7 @@
 
 if TYPE_CHECKING:
     from geventwebsocket.websocket import WebSocket
+    from eel.types import OptionsDictT
 
 from gevent.threading import Timer
 import gevent as gvt
@@ -41,7 +42,7 @@
 _js_result_timeout: int = 10000
 
 # All start() options must provide a default value and explanation here
-_start_args: dict[str, Any] = {
+_start_args: OptionsDictT = {
     'mode':             'chrome',                   # What browser is used
     'host':             'localhost',                # Hostname use for Bottle server
     'port':             8000,                       # Port used for Bottle server (use 0 for auto)
@@ -156,6 +157,8 @@ def start(*start_urls: str, **kwargs: Any) -> None:
 
     if _start_args['jinja_templates'] != None:
         from jinja2 import Environment, FileSystemLoader, select_autoescape
+        if not isinstance(_start_args['jinja_templates'], str):
+            raise TypeError("'jinja_templates start_arg/option must be of type str'")
         templates_path = os.path.join(root_path, _start_args['jinja_templates'])
         _start_args['jinja_env'] = Environment(loader=FileSystemLoader(templates_path),
                                  autoescape=select_autoescape(['html', 'xml']))
@@ -172,6 +175,8 @@ def run_lambda() -> None:
         if _start_args['all_interfaces'] == True:
             HOST = '0.0.0.0'
         else:
+            if not isinstance(_start_args['host'], str):
+                raise TypeError("'host' start_arg/option must be of type str")
             HOST = _start_args['host']
 
         app = _start_args['app']
@@ -200,7 +205,7 @@ def show(*start_urls: str) -> None:
 
 
 def sleep(seconds: int | float) -> None:
-    gvt.sleep(seconds) # type: ignore # gevent docs specify int | float, available stubs are wrong
+    gvt.sleep(seconds)
 
 
 def spawn(function: Callable[..., Any], *args: Any, **kwargs: Any) -> gvt.Greenlet:
@@ -222,15 +227,19 @@ def _eel() -> str:
     return page
 
 def _root() -> Optional[btl.Response]:
+    if not isinstance(_start_args['default_path'], str):
+        raise TypeError("'default_path' start_arg/option must be of type str")
     return _static(_start_args['default_path'])
 
 def _static(path: str) -> Optional[btl.HTTPResponse | btl.HTTPError]:
     response = None
     if 'jinja_env' in _start_args and 'jinja_templates' in _start_args:
+        if not isinstance(_start_args['jinja_templates'], str):
+            raise TypeError("'jinja_templates' start_arg/option must be of type str")
         template_prefix = _start_args['jinja_templates'] + '/'
         if path.startswith(template_prefix):
             n = len(template_prefix)
-            template = _start_args['jinja_env'].get_template(path[n:])
+            template = _start_args['jinja_env'].get_template(path[n:]) # type: ignore # depends on conditional import in start()
             response = btl.HTTPResponse(template.render())
 
     if response is None:
@@ -291,7 +300,7 @@ def _safe_json(obj: Any) -> str:
     return jsn.dumps(obj, default=lambda o: None)
 
 
-def _repeated_send(ws: WebSocket, msg: str):
+def _repeated_send(ws: WebSocket, msg: str) -> None:
     for attempt in range(100):
         try:
             ws.send(msg)
@@ -401,16 +410,18 @@ def _websocket_close(page: str) -> None:
     close_callback = _start_args.get('close_callback')
 
     if close_callback is not None:
+        if not callable(close_callback):
+            raise TypeError("'close_callback' start_arg/option must be callable or None")
         sockets = [p for _, p in _websockets]
         close_callback(page, sockets)
     else:
-        if _shutdown:
+        if isinstance(_shutdown, gvt.Greenlet):
             _shutdown.kill()
 
         _shutdown = gvt.spawn_later(_start_args['shutdown_delay'], _detect_shutdown)
 
 
-def _set_response_headers(response: btl.Response):
+def _set_response_headers(response: btl.Response) -> None:
     if _start_args['disable_cache']:
         # https://stackoverflow.com/a/24748094/280852
         response.set_header('Cache-Control', 'no-store')
diff --git a/eel/browsers.py b/eel/browsers.py
index 4b3ead68..e54fd495 100644
--- a/eel/browsers.py
+++ b/eel/browsers.py
@@ -4,6 +4,7 @@
 from typing import List, Dict, Iterable, Optional
 from types import ModuleType
 
+from eel.types import OptionsDictT
 import eel.chrome as chm
 import eel.electron as ele
 import eel.edge as edge
@@ -16,20 +17,24 @@
                                            'edge': edge}
 
 
-def _build_url_from_dict(page: Dict[str, str], options: Dict[str, str]) -> str:
+def _build_url_from_dict(page: Dict[str, str], options: OptionsDictT) -> str:
     scheme = page.get('scheme', 'http')
     host = page.get('host', 'localhost')
     port = page.get('port', options["port"])
     path = page.get('path', '')
+    if not isinstance(port, (int, str)):
+        raise TypeError("'port' option must be an integer")
     return '%s://%s:%d/%s' % (scheme, host, int(port), path)
 
 
-def _build_url_from_string(page: str, options: Dict[str, str]) -> str:
+def _build_url_from_string(page: str, options: OptionsDictT) -> str:
+    if not isinstance(options['port'], (int, str)):
+        raise TypeError("'port' option must be an integer")
     base_url = 'http://%s:%d/' % (options['host'], int(options['port']))
     return base_url + page
 
 
-def _build_urls(start_pages: Iterable[str | Dict[str, str]], options: Dict[str, str]) -> List[str]:
+def _build_urls(start_pages: Iterable[str | Dict[str, str]], options: OptionsDictT) -> List[str]:
     urls: List[str] = []
 
     for page in start_pages:
@@ -42,16 +47,20 @@ def _build_urls(start_pages: Iterable[str | Dict[str, str]], options: Dict[str,
     return urls
 
 
-def open(start_pages: Iterable[str | Dict[str, str]], options: Dict[str, str]) -> None:
+def open(start_pages: Iterable[str | Dict[str, str]], options: OptionsDictT) -> None:
     # Build full URLs for starting pages (including host and port)
     start_urls = _build_urls(start_pages, options)
     
     mode = options.get('mode')
-    if mode in [None, False]:
+    if not isinstance(mode, (str, bool, type(None))) or mode is True:
+        raise TypeError("'mode' option must by either a string, False, or None")
+    if mode is None or mode is False:
         # Don't open a browser
         pass
     elif mode == 'custom':
         # Just run whatever command the user provided
+        if not isinstance(options['cmdline_args'], list):
+            raise TypeError("'cmdline_args' option must be of type List[str]")
         sps.Popen(options['cmdline_args'],
                   stdout=sps.PIPE, stderr=sps.PIPE, stdin=sps.PIPE)
     elif mode in _browser_modules:
diff --git a/eel/chrome.py b/eel/chrome.py
index f3c233d2..9e212491 100644
--- a/eel/chrome.py
+++ b/eel/chrome.py
@@ -1,12 +1,16 @@
 from __future__ import annotations
 import sys, subprocess as sps, os
-from typing import Dict, List, Any, Optional
+from typing import List, Optional
+
+from eel.types import OptionsDictT
 
 # Every browser specific module must define run(), find_path() and name like this
 
 name: str = 'Google Chrome/Chromium'
 
-def run(path: str, options: Dict[str, Any], start_urls: List[str]) -> None:
+def run(path: str, options: OptionsDictT, start_urls: List[str]) -> None:
+    if not isinstance(options['cmdline_args'], list):
+        raise TypeError("'cmdline_args' option must be of type List[str]")
     if options['app_mode']:
         for url in start_urls:
             sps.Popen([path, '--app=%s' % url] +
@@ -63,7 +67,7 @@ def _find_chrome_linux() -> Optional[str]:
     for name in chrome_names:
         chrome = wch.which(name)
         if chrome is not None:
-            return chrome
+            return chrome # type: ignore # whichcraft doesn't currently have type hints
     return None
 
 
diff --git a/eel/edge.py b/eel/edge.py
index 9fcd9a50..631ecec1 100644
--- a/eel/edge.py
+++ b/eel/edge.py
@@ -2,12 +2,14 @@
 import platform
 import subprocess as sps
 import sys
-from typing import List, Dict, Any
+from typing import List
+
+from eel.types import OptionsDictT
 
 name: str = 'Edge'
 
 
-def run(_path: str, options: Dict[str, Any], start_urls: List[str]) -> None:
+def run(_path: str, options: OptionsDictT, start_urls: List[str]) -> None:
     cmd = 'start microsoft-edge:{}'.format(start_urls[0])
     sps.Popen(cmd, stdout=sys.stdout, stderr=sys.stderr, stdin=sps.PIPE, shell=True)
 
diff --git a/eel/electron.py b/eel/electron.py
index f5897535..974b2dd9 100644
--- a/eel/electron.py
+++ b/eel/electron.py
@@ -3,11 +3,15 @@
 import os
 import subprocess as sps
 import whichcraft as wch
-from typing import List, Dict, Any, Optional
+from typing import List, Optional
+
+from eel.types import OptionsDictT
 
 name: str = 'Electron'
 
-def run(path: str, options: Dict[str, Any], start_urls: List[str]):
+def run(path: str, options: OptionsDictT, start_urls: List[str]) -> None:
+    if not isinstance(options['cmdline_args'], list):
+        raise TypeError("'cmdline_args' option must be of type List[str]")
     cmd = [path] + options['cmdline_args']
     cmd += ['.', ';'.join(start_urls)]
     sps.Popen(cmd, stdout=sys.stdout, stderr=sys.stderr, stdin=sps.PIPE)
@@ -20,7 +24,7 @@ def find_path() -> Optional[str]:
         return os.path.join(bat_path, r'..\node_modules\electron\dist\electron.exe')
     elif sys.platform in ['darwin', 'linux']:
         # This should work find...
-        return wch.which('electron')
+        return wch.which('electron') # type: ignore # whichcraft doesn't currently have type hints
     else:
         return None
 
diff --git a/eel/py.typed b/eel/py.typed
new file mode 100644
index 00000000..e69de29b
diff --git a/eel/types.py b/eel/types.py
new file mode 100644
index 00000000..01fd0170
--- /dev/null
+++ b/eel/types.py
@@ -0,0 +1,15 @@
+from __future__ import annotations
+from typing import Dict, List, Tuple, Callable, Optional, Any, TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from jinja2 import Environment
+    Jinja2Environment = Environment
+else:
+    Jinja2Environment = None
+
+OptionsDictT = Dict[
+        str,
+        Optional[
+            str | bool | int | float | List[str] | Tuple[int, int] | Dict[str, Tuple[int, int]] | Callable[..., Any] | Jinja2Environment
+        ]
+    ]
\ No newline at end of file