diff --git a/custom_components/violet_pool_controller/config_flow.py b/custom_components/violet_pool_controller/config_flow.py
index 3a383fd..fa572c4 100644
--- a/custom_components/violet_pool_controller/config_flow.py
+++ b/custom_components/violet_pool_controller/config_flow.py
@@ -1,31 +1,61 @@
+import logging
+
+import aiohttp
+import async_timeout
 import voluptuous as vol
 from homeassistant import config_entries
 from homeassistant.core import callback
+from homeassistant.data_entry_flow import FlowResult
+from homeassistant.helpers import aiohttp_client
+from homeassistant.helpers.selector import TextSelector
 
 from .const import DOMAIN, CONF_API_URL, CONF_POLLING_INTERVAL
 
-@callback
-def configured_instances(hass):
-    """Return a set of configured instances."""
-    return set(entry.data[CONF_API_URL] for entry in hass.config_entries.async_entries(DOMAIN))
+_LOGGER = logging.getLogger(__name__)
+
 
 class VioletDeviceConfigFlow(config_entries.ConfigFlow, domain=DOMAIN):
     """Handle a config flow for Violet Device."""
 
     VERSION = 1
-    CONNECTION_CLASS = config_entries.CONN_CLASS_LOCAL_POLL
 
-    async def async_step_user(self, user_input=None):
+    async def async_step_user(self, user_input=None) -> FlowResult:
         """Handle the initial step."""
+        errors = {}
+
         if user_input is not None:
-            # Save the user input
-            return self.async_create_entry(title="Violet Device", data=user_input)
+            api_url = user_input[CONF_API_URL]
+
+            # Check for duplicate entries
+            await self.async_set_unique_id(api_url)
+            self._abort_if_unique_id_configured()
+
+            # Validate the API URL
+            session = aiohttp_client.async_get_clientsession(self.hass)
+            try:
+                async with async_timeout.timeout(10):
+                    async with session.get(api_url, ssl=False) as response:
+                        response.raise_for_status()
+                        await response.json()
+            except aiohttp.ClientError as err:
+                _LOGGER.error("Error connecting to API: %s", err)
+                errors["base"] = "cannot_connect"
+            except Exception as err:
+                _LOGGER.error("Unexpected exception: %s", err)
+                errors["base"] = "unknown"
+            else:
+                # Input is valid, create the config entry
+                return self.async_create_entry(title="Violet Device", data=user_input)
+
+        # Show the configuration form with errors (if any)
+        data_schema = vol.Schema({
+            vol.Required(CONF_API_URL, default="http://192.168.178.55/getReadings?ALL"): str,
+            vol.Optional(CONF_POLLING_INTERVAL, default=10): int,
+        })
 
-        # Show the configuration form
         return self.async_show_form(
             step_id="user",
-            data_schema=vol.Schema({
-                vol.Required(CONF_API_URL, default="http://192.168.178.55/getReadings?ALL"): str,
-                vol.Optional(CONF_POLLING_INTERVAL, default=10): int,
-            })
+            data_schema=data_schema,
+            errors=errors,
         )
+