diff --git a/src/api/api.ts b/src/api/api.ts
index 43322e4..ecc14ca 100644
--- a/src/api/api.ts
+++ b/src/api/api.ts
@@ -15,7 +15,6 @@ export const getChatCompletion = async (
     method: 'POST',
     headers,
     body: JSON.stringify({
-      model: 'gpt-3.5-turbo',
       messages,
       ...config,
     }),
@@ -41,16 +40,24 @@ export const getChatCompletionStream = async (
     method: 'POST',
     headers,
     body: JSON.stringify({
-      model: 'gpt-3.5-turbo',
       messages,
       ...config,
       stream: true,
     }),
   });
-  if (response.status === 404 || response.status === 405)
-    throw new Error(
-      'Message from freechatgpt.chat:\nInvalid API endpoint! We recommend you to check your free API endpoint.'
-    );
+  if (response.status === 404 || response.status === 405) {
+    const text = await response.text();
+    if (text.includes('model_not_found')) {
+      throw new Error(
+        text +
+          '\nMessage from freechatgpt.chat:\nPlease ensure that you have access to the GPT-4 API!'
+      );
+    } else {
+      throw new Error(
+        'Message from freechatgpt.chat:\nInvalid API endpoint! We recommend you to check your free API endpoint.'
+      );
+    }
+  }
 
   if (response.status === 429 || !response.ok) {
     const text = await response.text();
diff --git a/src/api/customApi.ts b/src/api/customApi.ts
index 96a6cde..65fcccf 100644
--- a/src/api/customApi.ts
+++ b/src/api/customApi.ts
@@ -33,7 +33,6 @@ export const getChatCompletion = async (
       Authorization: `Bearer ${apiKey}`,
     },
     body: JSON.stringify({
-      model: 'gpt-3.5-turbo',
       messages,
       ...config,
     }),
@@ -56,7 +55,6 @@ export const getChatCompletionStream = async (
       Authorization: `Bearer ${apiKey}`,
     },
     body: JSON.stringify({
-      model: 'gpt-3.5-turbo',
       messages,
       ...config,
       stream: true,
diff --git a/src/api/freeApi.ts b/src/api/freeApi.ts
index 25e6e7a..ac8a754 100644
--- a/src/api/freeApi.ts
+++ b/src/api/freeApi.ts
@@ -11,7 +11,6 @@ export const getChatCompletion = async (
       'Content-Type': 'application/json',
     },
     body: JSON.stringify({
-      model: 'gpt-3.5-turbo',
       messages,
       ...config,
     }),
@@ -33,7 +32,6 @@ export const getChatCompletionStream = async (
       'Content-Type': 'application/json',
     },
     body: JSON.stringify({
-      model: 'gpt-3.5-turbo',
       messages,
       ...config,
       stream: true,
diff --git a/src/components/Chat/ChatContent/ChatTitle.tsx b/src/components/Chat/ChatContent/ChatTitle.tsx
index 2cdb3fa..4267b8a 100644
--- a/src/components/Chat/ChatContent/ChatTitle.tsx
+++ b/src/components/Chat/ChatContent/ChatTitle.tsx
@@ -49,7 +49,7 @@ const ChatTitle = React.memo(() => {
         }}
       >
         <div className='text-center p-1 rounded-md bg-gray-300/20 dark:bg-gray-900/10 hover:bg-gray-300/50 dark:hover:bg-gray-900/50'>
-          {t('model')}: {t('default')}
+          {t('model')}: {config.model}
         </div>
         <div className='text-center p-1 rounded-md bg-gray-300/20 dark:bg-gray-900/10 hover:bg-gray-300/50 dark:hover:bg-gray-900/50'>
           {t('temperature.label')}: {config.temperature}
diff --git a/src/components/ConfigMenu/ConfigMenu.tsx b/src/components/ConfigMenu/ConfigMenu.tsx
index a12c600..ee115de 100644
--- a/src/components/ConfigMenu/ConfigMenu.tsx
+++ b/src/components/ConfigMenu/ConfigMenu.tsx
@@ -1,7 +1,10 @@
 import React, { useState } from 'react';
+import useStore from '@store/store';
 import { useTranslation } from 'react-i18next';
 import PopupModal from '@components/PopupModal';
-import { ConfigInterface } from '@type/chat';
+import { ConfigInterface, ModelOptions } from '@type/chat';
+import DownChevronArrow from '@icon/DownChevronArrow';
+import { modelOptions } from '@constants/chat';
 
 const ConfigMenu = ({
   setIsModalOpen,
@@ -12,18 +15,24 @@ const ConfigMenu = ({
   config: ConfigInterface;
   setConfig: (config: ConfigInterface) => void;
 }) => {
+  const [_model, _setModel] = useState<ModelOptions>(config.model);
   const [_temperature, _setTemperature] = useState<number>(config.temperature);
-  const [_presencePenalty, _setPresencePenalty] = useState<number>(config.presence_penalty);
+  const [_presencePenalty, _setPresencePenalty] = useState<number>(
+    config.presence_penalty
+  );
   const [_topP, _setTopP] = useState<number>(config.top_p);
-  const [_frequencyPenalty, _setFrequencyPenalty] = useState<number>(config.frequency_penalty);
+  const [_frequencyPenalty, _setFrequencyPenalty] = useState<number>(
+    config.frequency_penalty
+  );
   const { t } = useTranslation('model');
 
   const handleConfirm = () => {
     setConfig({
+      model: _model,
       temperature: _temperature,
       presence_penalty: _presencePenalty,
       top_p: _topP,
-      frequency_penalty: _frequencyPenalty
+      frequency_penalty: _frequencyPenalty,
     });
     setIsModalOpen(false);
   };
@@ -35,6 +44,7 @@ const ConfigMenu = ({
       handleConfirm={handleConfirm}
     >
       <div className='p-6 border-b border-gray-200 dark:border-gray-600'>
+        <ModelSelector _model={_model} _setModel={_setModel} />
         <div>
           <label className='block text-sm font-medium text-gray-900 dark:text-white'>
             {t('temperature.label')}: {_temperature}
@@ -120,4 +130,51 @@ const ConfigMenu = ({
   );
 };
 
+const ModelSelector = ({
+  _model,
+  _setModel,
+}: {
+  _model: ModelOptions;
+  _setModel: React.Dispatch<React.SetStateAction<ModelOptions>>;
+}) => {
+  const [dropDown, setDropDown] = useState<boolean>(false);
+
+  return (
+    <div className='mb-4'>
+      <button
+        className='btn btn-neutral btn-small flex gap-1'
+        type='button'
+        onClick={() => setDropDown((prev) => !prev)}
+      >
+        {_model}
+        <DownChevronArrow />
+      </button>
+      <div
+        id='dropdown'
+        className={`${
+          dropDown ? '' : 'hidden'
+        } absolute top-100 bottom-100 z-10 bg-white rounded-lg shadow-xl border-b border-black/10 dark:border-gray-900/50 text-gray-800 dark:text-gray-100 group dark:bg-gray-800 opacity-90`}
+      >
+        <ul
+          className='text-sm text-gray-700 dark:text-gray-200 p-0 m-0'
+          aria-labelledby='dropdownDefaultButton'
+        >
+          {modelOptions.map((m) => (
+            <li
+              className='px-4 py-2 hover:bg-gray-100 dark:hover:bg-gray-600 dark:hover:text-white cursor-pointer'
+              onClick={() => {
+                _setModel(m);
+                setDropDown(false);
+              }}
+              key={m}
+            >
+              {m}
+            </li>
+          ))}
+        </ul>
+      </div>
+    </div>
+  );
+};
+
 export default ConfigMenu;
diff --git a/src/constants/chat.ts b/src/constants/chat.ts
index 44fe481..d07b66f 100644
--- a/src/constants/chat.ts
+++ b/src/constants/chat.ts
@@ -1,4 +1,4 @@
-import { ChatInterface, ConfigInterface } from '@type/chat';
+import { ChatInterface, ConfigInterface, ModelOptions } from '@type/chat';
 
 const date = new Date();
 const dateString =
@@ -13,11 +13,23 @@ export const defaultSystemMessage = `You are ChatGPT, a large language model tra
 Knowledge cutoff: 2021-09
 Current date: ${dateString}`;
 
+export const modelOptions: ModelOptions[] = [
+  'gpt-3.5-turbo',
+  // 'gpt-3.5-turbo-0301',
+  'gpt-4',
+  // 'gpt-4-0314',
+  // 'gpt-4-32k',
+  // 'gpt-4-32k-0314',
+];
+
+export const defaultModel = 'gpt-3.5-turbo';
+
 export const defaultChatConfig: ConfigInterface = {
+  model: defaultModel,
   temperature: 1,
   presence_penalty: 0,
   top_p: 1,
-  frequency_penalty: 0
+  frequency_penalty: 0,
 };
 
 export const generateDefaultChat = (title?: string): ChatInterface => ({
diff --git a/src/store/migrate.ts b/src/store/migrate.ts
index c3576d6..71adbc0 100644
--- a/src/store/migrate.ts
+++ b/src/store/migrate.ts
@@ -3,8 +3,9 @@ import {
   LocalStorageInterfaceV1ToV2,
   LocalStorageInterfaceV2ToV3,
   LocalStorageInterfaceV3ToV4,
+  LocalStorageInterfaceV4ToV5,
 } from '@type/chat';
-import { defaultChatConfig } from '@constants/chat';
+import { defaultChatConfig, defaultModel } from '@constants/chat';
 import { officialAPIEndpoint } from '@constants/auth';
 import defaultPrompts from '@constants/prompt';
 
@@ -37,3 +38,12 @@ export const migrateV2 = (persistedState: LocalStorageInterfaceV2ToV3) => {
 export const migrateV3 = (persistedState: LocalStorageInterfaceV3ToV4) => {
   persistedState.prompts = defaultPrompts;
 };
+
+export const migrateV4 = (persistedState: LocalStorageInterfaceV4ToV5) => {
+  persistedState.chats.forEach((chat) => {
+    chat.config = {
+      ...chat.config,
+      model: defaultModel,
+    };
+  });
+};
diff --git a/src/store/store.ts b/src/store/store.ts
index a337e5b..294a0d3 100644
--- a/src/store/store.ts
+++ b/src/store/store.ts
@@ -10,8 +10,15 @@ import {
   LocalStorageInterfaceV1ToV2,
   LocalStorageInterfaceV2ToV3,
   LocalStorageInterfaceV3ToV4,
+  LocalStorageInterfaceV4ToV5,
 } from '@type/chat';
-import { migrateV0, migrateV1, migrateV2, migrateV3 } from './migrate';
+import {
+  migrateV0,
+  migrateV1,
+  migrateV2,
+  migrateV3,
+  migrateV4,
+} from './migrate';
 
 export type StoreState = ChatSlice &
   InputSlice &
@@ -45,7 +52,7 @@ const useStore = create<StoreState>()(
         autoTitle: state.autoTitle,
         prompts: state.prompts,
       }),
-      version: 4,
+      version: 5,
       migrate: (persistedState, version) => {
         switch (version) {
           case 0:
@@ -56,6 +63,8 @@ const useStore = create<StoreState>()(
             migrateV2(persistedState as LocalStorageInterfaceV2ToV3);
           case 3:
             migrateV3(persistedState as LocalStorageInterfaceV3ToV4);
+          case 4:
+            migrateV4(persistedState as LocalStorageInterfaceV4ToV5);
             break;
         }
         return persistedState as StoreState;
diff --git a/src/types/chat.ts b/src/types/chat.ts
index e227d9e..99985d5 100644
--- a/src/types/chat.ts
+++ b/src/types/chat.ts
@@ -17,12 +17,21 @@ export interface ChatInterface {
 }
 
 export interface ConfigInterface {
+  model: ModelOptions;
   temperature: number;
   presence_penalty: number;
   top_p: number;
   frequency_penalty: number;
 }
 
+export type ModelOptions =
+  | 'gpt-4'
+  | 'gpt-4-0314'
+  | 'gpt-4-32k'
+  | 'gpt-4-32k-0314'
+  | 'gpt-3.5-turbo'
+  | 'gpt-3.5-turbo-0301';
+
 export interface LocalStorageInterfaceV0ToV1 {
   chats: ChatInterface[];
   currentChatIndex: number;
@@ -63,3 +72,15 @@ export interface LocalStorageInterfaceV3ToV4 {
   autoTitle: boolean;
   prompts: Prompt[];
 }
+
+export interface LocalStorageInterfaceV4ToV5 {
+  chats: ChatInterface[];
+  currentChatIndex: number;
+  apiKey: string;
+  apiFree: boolean;
+  apiFreeEndpoint: string;
+  apiEndpoint?: string;
+  theme: Theme;
+  autoTitle: boolean;
+  prompts: Prompt[];
+}