diff --git a/.storybook/preview.js b/.storybook/preview.js
index 9260b91c98..2f611743f2 100644
--- a/.storybook/preview.js
+++ b/.storybook/preview.js
@@ -2,14 +2,14 @@ import React from 'react';
 import { Provider } from 'react-redux';
 import { MemoryRouter } from 'react-router';
 
-import configureStore from '../client/store';
+import { setupStore } from '../client/store';
 import '../client/i18n-test';
-import '../client/styles/storybook.css'
+import '../client/styles/storybook.css';
 import { withThemeProvider, themeToolbarItem } from './decorator-theme';
 
 const initialState = window.__INITIAL_STATE__;
 
-const store = configureStore(initialState);
+const store = setupStore(initialState);
 
 export const decorators = [
   (Story) => (
diff --git a/client/custom.d.ts b/client/custom.d.ts
index 216fa99ad4..729f9e03de 100644
--- a/client/custom.d.ts
+++ b/client/custom.d.ts
@@ -4,5 +4,18 @@ declare module '*.svg' {
   const ReactComponent: React.FunctionComponent<
     React.SVGProps<SVGSVGElement> & { title?: string }
   >;
+  // eslint-disable-next-line import/no-default-export
   export default ReactComponent;
 }
+
+// Extend window for Redux DevTools
+interface Window {
+  __REDUX_DEVTOOLS_EXTENSION__?: () => any;
+}
+
+// Extend NodeModule for hot reloading
+interface NodeModule {
+  hot?: {
+    accept(path?: string, callback?: () => void): void;
+  };
+}
diff --git a/client/index.integration.test.jsx b/client/index.integration.test.jsx
index 66819b1536..f27971b7b9 100644
--- a/client/index.integration.test.jsx
+++ b/client/index.integration.test.jsx
@@ -4,13 +4,13 @@ import React from 'react';
 import Routing from './routes';
 
 import { reduxRender, act, waitFor, screen, within } from './test-utils';
-import configureStore from './store';
+import { setupStore } from './store';
 import * as Actions from './modules/User/actions';
 import { userResponse } from './testData/testServerResponses';
 
 // setup for the app
 const initialState = window.__INITIAL_STATE__;
-const store = configureStore(initialState);
+const store = setupStore(initialState);
 
 // need to mock this file or it'll throw ERRCONNECTED
 jest.mock('./i18n');
diff --git a/client/index.jsx b/client/index.jsx
index c4c53c1186..4b79e95f12 100644
--- a/client/index.jsx
+++ b/client/index.jsx
@@ -5,7 +5,7 @@ import { Router } from 'react-router-dom';
 
 import { useTranslation } from 'react-i18next';
 import browserHistory from './browserHistory';
-import configureStore from './store';
+import { setupStore } from './store';
 import Routing from './routes';
 import ThemeProvider from './modules/App/components/ThemeProvider';
 import Loader from './modules/App/components/loader';
@@ -19,7 +19,7 @@ require('./images/p5js-square-logo.png');
 
 const initialState = window.__INITIAL_STATE__;
 
-const store = configureStore(initialState);
+const store = setupStore(initialState);
 
 const DONATE_LOGO_IMAGE_URL = 'https://donorbox.org/images/white_logo.svg';
 
diff --git a/client/modules/IDE/actions/preferences.js b/client/modules/IDE/actions/preferences.ts
similarity index 62%
rename from client/modules/IDE/actions/preferences.js
rename to client/modules/IDE/actions/preferences.ts
index f6e71504ee..ccb5ef6a63 100644
--- a/client/modules/IDE/actions/preferences.js
+++ b/client/modules/IDE/actions/preferences.ts
@@ -1,8 +1,30 @@
 import i18next from 'i18next';
+import { UpdatePreferencesRequestBody } from '../../../../common/types';
 import { apiClient } from '../../../utils/apiClient';
 import * as ActionTypes from '../../../constants';
+import type {
+  UpdatePreferencesDispatch,
+  SetPreferencesTabValue,
+  SetFontSizeValue,
+  GetRootState,
+  SetLineNumbersValue,
+  SetAutocloseBracketsQuotesValue,
+  SetAutocompleteHinterValue,
+  SetAutosaveValue,
+  SetLinewrapValue,
+  SetLintWarningValue,
+  SetTextOutputValue,
+  SetAllAccessibleOutputValue,
+  SetAutorefreshValue,
+  SetGridOutputValue,
+  SetLanguageValue,
+  SetThemeValue
+} from './preferences.types';
 
-function updatePreferences(formParams, dispatch) {
+function updatePreferences(
+  formParams: UpdatePreferencesRequestBody,
+  dispatch: UpdatePreferencesDispatch
+) {
   apiClient
     .put('/preferences', formParams)
     .then(() => {})
@@ -14,15 +36,15 @@ function updatePreferences(formParams, dispatch) {
     });
 }
 
-export function setPreferencesTab(value) {
+export function setPreferencesTab(value: SetPreferencesTabValue) {
   return {
     type: ActionTypes.SET_PREFERENCES_TAB,
     value
   };
 }
 
-export function setFontSize(value) {
-  return (dispatch, getState) => {
+export function setFontSize(value: SetFontSizeValue) {
+  return (dispatch: UpdatePreferencesDispatch, getState: GetRootState) => {
     // eslint-disable-line
     dispatch({
       type: ActionTypes.SET_FONT_SIZE,
@@ -40,8 +62,8 @@ export function setFontSize(value) {
   };
 }
 
-export function setLineNumbers(value) {
-  return (dispatch, getState) => {
+export function setLineNumbers(value: SetLineNumbersValue) {
+  return (dispatch: UpdatePreferencesDispatch, getState: GetRootState) => {
     dispatch({
       type: ActionTypes.SET_LINE_NUMBERS,
       value
@@ -58,8 +80,10 @@ export function setLineNumbers(value) {
   };
 }
 
-export function setAutocloseBracketsQuotes(value) {
-  return (dispatch, getState) => {
+export function setAutocloseBracketsQuotes(
+  value: SetAutocloseBracketsQuotesValue
+) {
+  return (dispatch: UpdatePreferencesDispatch, getState: GetRootState) => {
     dispatch({
       type: ActionTypes.SET_AUTOCLOSE_BRACKETS_QUOTES,
       value
@@ -76,8 +100,8 @@ export function setAutocloseBracketsQuotes(value) {
   };
 }
 
-export function setAutocompleteHinter(value) {
-  return (dispatch, getState) => {
+export function setAutocompleteHinter(value: SetAutocompleteHinterValue) {
+  return (dispatch: UpdatePreferencesDispatch, getState: GetRootState) => {
     dispatch({
       type: ActionTypes.SET_AUTOCOMPLETE_HINTER,
       value
@@ -94,8 +118,8 @@ export function setAutocompleteHinter(value) {
   };
 }
 
-export function setAutosave(value) {
-  return (dispatch, getState) => {
+export function setAutosave(value: SetAutosaveValue) {
+  return (dispatch: UpdatePreferencesDispatch, getState: GetRootState) => {
     dispatch({
       type: ActionTypes.SET_AUTOSAVE,
       value
@@ -112,8 +136,8 @@ export function setAutosave(value) {
   };
 }
 
-export function setLinewrap(value) {
-  return (dispatch, getState) => {
+export function setLinewrap(value: SetLinewrapValue) {
+  return (dispatch: UpdatePreferencesDispatch, getState: GetRootState) => {
     dispatch({
       type: ActionTypes.SET_LINEWRAP,
       value
@@ -130,8 +154,8 @@ export function setLinewrap(value) {
   };
 }
 
-export function setLintWarning(value) {
-  return (dispatch, getState) => {
+export function setLintWarning(value: SetLintWarningValue) {
+  return (dispatch: UpdatePreferencesDispatch, getState: GetRootState) => {
     dispatch({
       type: ActionTypes.SET_LINT_WARNING,
       value
@@ -148,8 +172,8 @@ export function setLintWarning(value) {
   };
 }
 
-export function setTextOutput(value) {
-  return (dispatch, getState) => {
+export function setTextOutput(value: SetTextOutputValue) {
+  return (dispatch: UpdatePreferencesDispatch, getState: GetRootState) => {
     dispatch({
       type: ActionTypes.SET_TEXT_OUTPUT,
       value
@@ -166,8 +190,8 @@ export function setTextOutput(value) {
   };
 }
 
-export function setGridOutput(value) {
-  return (dispatch, getState) => {
+export function setGridOutput(value: SetGridOutputValue) {
+  return (dispatch: UpdatePreferencesDispatch, getState: GetRootState) => {
     dispatch({
       type: ActionTypes.SET_GRID_OUTPUT,
       value
@@ -184,12 +208,8 @@ export function setGridOutput(value) {
   };
 }
 
-export function setTheme(value) {
-  // return {
-  //   type: ActionTypes.SET_THEME,
-  //   value
-  // };
-  return (dispatch, getState) => {
+export function setTheme(value: SetThemeValue) {
+  return (dispatch: UpdatePreferencesDispatch, getState: GetRootState) => {
     dispatch({
       type: ActionTypes.SET_THEME,
       value
@@ -206,12 +226,8 @@ export function setTheme(value) {
   };
 }
 
-export function setAutorefresh(value) {
-  // return {
-  //   type: ActionTypes.SET_AUTOREFRESH,
-  //   value
-  // };
-  return (dispatch, getState) => {
+export function setAutorefresh(value: SetAutorefreshValue) {
+  return (dispatch: UpdatePreferencesDispatch, getState: GetRootState) => {
     dispatch({
       type: ActionTypes.SET_AUTOREFRESH,
       value
@@ -228,15 +244,18 @@ export function setAutorefresh(value) {
   };
 }
 
-export function setAllAccessibleOutput(value) {
-  return (dispatch) => {
+export function setAllAccessibleOutput(value: SetAllAccessibleOutputValue) {
+  return (dispatch: UpdatePreferencesDispatch, getState: GetRootState) => {
     dispatch(setTextOutput(value));
     dispatch(setGridOutput(value));
   };
 }
 
-export function setLanguage(value, { persistPreference = true } = {}) {
-  return (dispatch, getState) => {
+export function setLanguage(
+  value: SetLanguageValue,
+  { persistPreference = true } = {}
+) {
+  return (dispatch: UpdatePreferencesDispatch, getState: GetRootState) => {
     i18next.changeLanguage(value);
     dispatch({
       type: ActionTypes.SET_LANGUAGE,
diff --git a/client/modules/IDE/actions/preferences.types.ts b/client/modules/IDE/actions/preferences.types.ts
new file mode 100644
index 0000000000..e54d28d3cd
--- /dev/null
+++ b/client/modules/IDE/actions/preferences.types.ts
@@ -0,0 +1,116 @@
+import * as ActionTypes from '../../../constants';
+import type { PreferencesState } from '../reducers/preferences';
+import type { RootState } from '../../../reducers';
+
+// Value Definitions:
+export type SetPreferencesTabValue = PreferencesState['tabIndex'];
+export type SetFontSizeValue = PreferencesState['fontSize'];
+export type SetLineNumbersValue = PreferencesState['lineNumbers'];
+export type SetAutocloseBracketsQuotesValue = PreferencesState['autocloseBracketsQuotes'];
+export type SetAutocompleteHinterValue = PreferencesState['autocompleteHinter'];
+export type SetAutosaveValue = PreferencesState['autosave'];
+export type SetLinewrapValue = PreferencesState['linewrap'];
+export type SetLintWarningValue = PreferencesState['lintWarning'];
+export type SetTextOutputValue = PreferencesState['textOutput'];
+export type SetGridOutputValue = PreferencesState['gridOutput'];
+export type SetThemeValue = PreferencesState['theme'];
+export type SetAutorefreshValue = PreferencesState['autorefresh'];
+export type SetLanguageValue = PreferencesState['language'];
+export type SetAllAccessibleOutputValue =
+  | SetTextOutputValue
+  | SetGridOutputValue;
+
+// Action Definitions:
+export type OpenPreferencesAction = {
+  type: typeof ActionTypes.OPEN_PREFERENCES;
+};
+export type SetPreferencesAction = {
+  type: typeof ActionTypes.SET_PREFERENCES;
+  preferences: PreferencesState;
+};
+export type SetErrorAction = {
+  type: typeof ActionTypes.ERROR;
+  error: unknown;
+};
+
+export type SetPreferencesTabAction = {
+  type: typeof ActionTypes.SET_PREFERENCES_TAB;
+  value: SetPreferencesTabValue;
+};
+export type SetFontSizeAction = {
+  type: typeof ActionTypes.SET_FONT_SIZE;
+  value: SetFontSizeValue;
+};
+export type SetLineNumbersAction = {
+  type: typeof ActionTypes.SET_LINE_NUMBERS;
+  value: SetLineNumbersValue;
+};
+export type SetAutocloseBracketsQuotesAction = {
+  type: typeof ActionTypes.SET_AUTOCLOSE_BRACKETS_QUOTES;
+  value: SetAutocloseBracketsQuotesValue;
+};
+export type SetAutocompleteHinterAction = {
+  type: typeof ActionTypes.SET_AUTOCOMPLETE_HINTER;
+  value: SetAutocompleteHinterValue;
+};
+export type SetAutosaveAction = {
+  type: typeof ActionTypes.SET_AUTOSAVE;
+  value: SetAutosaveValue;
+};
+export type SetLinewrapAction = {
+  type: typeof ActionTypes.SET_LINEWRAP;
+  value: SetLinewrapValue;
+};
+export type SetLintWarningAction = {
+  type: typeof ActionTypes.SET_LINT_WARNING;
+  value: SetLintWarningValue;
+};
+export type SetTextOutputAction = {
+  type: typeof ActionTypes.SET_TEXT_OUTPUT;
+  value: SetTextOutputValue;
+};
+export type SetGridOutputAction = {
+  type: typeof ActionTypes.SET_GRID_OUTPUT;
+  value: SetGridOutputValue;
+};
+export type SetThemeAction = {
+  type: typeof ActionTypes.SET_THEME;
+  value: SetThemeValue;
+};
+export type SetAutorefreshAction = {
+  type: typeof ActionTypes.SET_AUTOREFRESH;
+  value: SetAutorefreshValue;
+};
+export type SetLanguageAction = {
+  type: typeof ActionTypes.SET_LANGUAGE;
+  language: SetLanguageValue;
+};
+
+export type PreferencesAction =
+  | OpenPreferencesAction
+  | SetPreferencesAction
+  | SetErrorAction
+  | SetPreferencesTabAction
+  | SetFontSizeAction
+  | SetLineNumbersAction
+  | SetAutocloseBracketsQuotesAction
+  | SetAutocompleteHinterAction
+  | SetAutosaveAction
+  | SetLinewrapAction
+  | SetLintWarningAction
+  | SetTextOutputAction
+  | SetGridOutputAction
+  | SetThemeAction
+  | SetAutorefreshAction
+  | SetLanguageAction;
+
+export type UpdatePreferencesDispatch = (
+  action: PreferencesAction | PreferencesThunk
+) => void;
+
+export type PreferencesThunk = (
+  dispatch: UpdatePreferencesDispatch,
+  getState: GetRootState
+) => void;
+
+export type GetRootState = () => RootState;
diff --git a/client/modules/IDE/reducers/preferences.js b/client/modules/IDE/reducers/preferences.ts
similarity index 80%
rename from client/modules/IDE/reducers/preferences.js
rename to client/modules/IDE/reducers/preferences.ts
index d6323c4fd2..f890bb2ccb 100644
--- a/client/modules/IDE/reducers/preferences.js
+++ b/client/modules/IDE/reducers/preferences.ts
@@ -1,7 +1,17 @@
+import {
+  UserPreferences as Preferences,
+  AppThemeOptions
+} from '../../../../common/types';
 import * as ActionTypes from '../../../constants';
 import i18n from '../../../i18n';
+import type { PreferencesAction } from '../actions/preferences.types';
 
-export const initialState = {
+export interface PreferencesState
+  extends Omit<Preferences, 'indentationAmount' | 'isTabIndent'> {
+  tabIndex: number;
+}
+
+export const initialState: PreferencesState = {
   tabIndex: 0,
   fontSize: 18,
   autosave: true,
@@ -10,14 +20,17 @@ export const initialState = {
   lintWarning: false,
   textOutput: false,
   gridOutput: false,
-  theme: 'light',
+  theme: AppThemeOptions.LIGHT,
   autorefresh: false,
   language: i18n.language,
   autocloseBracketsQuotes: true,
   autocompleteHinter: false
 };
 
-const preferences = (state = initialState, action) => {
+export const preferences = (
+  state: PreferencesState = initialState,
+  action: PreferencesAction
+) => {
   switch (action.type) {
     case ActionTypes.OPEN_PREFERENCES:
       return Object.assign({}, state, { tabIndex: 0 });
@@ -57,5 +70,3 @@ const preferences = (state = initialState, action) => {
       return state;
   }
 };
-
-export default preferences;
diff --git a/client/persistState.js b/client/persistState.ts
similarity index 68%
rename from client/persistState.js
rename to client/persistState.ts
index 457dba016b..ceff31435e 100644
--- a/client/persistState.js
+++ b/client/persistState.ts
@@ -1,3 +1,4 @@
+import type { RootState } from './reducers';
 /*
   Saves and loads a snapshot of the Redux store
   state to session storage
@@ -5,7 +6,7 @@
 const key = 'p5js-editor';
 const storage = sessionStorage;
 
-export const saveState = (state) => {
+export const saveState = (state: RootState) => {
   try {
     storage.setItem(key, JSON.stringify(state));
   } catch (error) {
@@ -15,7 +16,9 @@ export const saveState = (state) => {
 
 export const loadState = () => {
   try {
-    return JSON.parse(storage.getItem(key));
+    const stored = storage.getItem(key);
+    if (!stored) return null; // handle null before parsing
+    return JSON.parse(stored) as RootState;
   } catch (error) {
     console.warn('Failed to retrieve initialize state from storage:', error);
     return null;
diff --git a/client/reducers.js b/client/reducers.ts
similarity index 82%
rename from client/reducers.js
rename to client/reducers.ts
index f61d2585d6..2c65e555ca 100644
--- a/client/reducers.js
+++ b/client/reducers.ts
@@ -1,7 +1,7 @@
 import { combineReducers } from 'redux';
 import files from './modules/IDE/reducers/files';
 import ide from './modules/IDE/reducers/ide';
-import preferences from './modules/IDE/reducers/preferences';
+import { preferences } from './modules/IDE/reducers/preferences';
 import project from './modules/IDE/reducers/project';
 import editorAccessibility from './modules/IDE/reducers/editorAccessibility';
 import user from './modules/User/reducers';
@@ -31,4 +31,8 @@ const rootReducer = combineReducers({
   collections
 });
 
+// Type for entire redux state
+export type RootState = ReturnType<typeof rootReducer>;
+
+// eslint-disable-next-line import/no-default-export
 export default rootReducer;
diff --git a/client/store.js b/client/store.ts
similarity index 93%
rename from client/store.js
rename to client/store.ts
index e74248f010..4ff0e566fd 100644
--- a/client/store.js
+++ b/client/store.ts
@@ -2,6 +2,7 @@ import { configureStore } from '@reduxjs/toolkit';
 import listenerMiddleware from './middleware';
 import DevTools from './modules/App/components/DevTools';
 import rootReducer from './reducers';
+import type { RootState } from './reducers';
 import { clearState, loadState } from './persistState';
 import { getConfig } from './utils/getConfig';
 
@@ -15,7 +16,7 @@ export function showReduxDevTools() {
   );
 }
 
-export default function setupStore(initialState) {
+export function setupStore(initialState: RootState) {
   const savedState = loadState();
   clearState();
 
diff --git a/client/storeInstance.js b/client/storeInstance.js
deleted file mode 100644
index bd92360c2e..0000000000
--- a/client/storeInstance.js
+++ /dev/null
@@ -1,6 +0,0 @@
-import setupStore from './store';
-
-const initialState = window.__INITIAL_STATE__;
-const store = setupStore(initialState);
-
-export default store;
diff --git a/client/test-utils.js b/client/test-utils.js
index 9b7c8aab31..4e0aca0e79 100644
--- a/client/test-utils.js
+++ b/client/test-utils.js
@@ -23,7 +23,7 @@ import { Context as ResponsiveContext } from 'react-responsive';
 
 import i18n from './i18n-test';
 import ThemeProvider from './modules/App/components/ThemeProvider';
-import configureStore from './store';
+import { setupStore } from './store';
 import theme, { Theme } from './theme';
 
 export const history = createMemoryHistory();
@@ -95,7 +95,7 @@ Providers.propTypes = {
  */
 function reduxRender(
   ui,
-  { initialState, store = configureStore(initialState), ...renderOptions } = {}
+  { initialState, store = setupStore(initialState), ...renderOptions } = {}
 ) {
   function Wrapper({ children }) {
     return (
diff --git a/client/testData/testReduxStore.js b/client/testData/testReduxStore.ts
similarity index 96%
rename from client/testData/testReduxStore.js
rename to client/testData/testReduxStore.ts
index f9f5d01925..33223ae950 100644
--- a/client/testData/testReduxStore.js
+++ b/client/testData/testReduxStore.ts
@@ -1,5 +1,6 @@
 import { initialState as initialFilesState } from '../modules/IDE/reducers/files';
 import { initialState as initialPrefState } from '../modules/IDE/reducers/preferences';
+import { RootState } from '../reducers';
 
 const mockProjects = [
   {
@@ -22,7 +23,7 @@ const mockProjects = [
   }
 ];
 
-const initialTestState = {
+const initialTestState: RootState = {
   ide: {
     isPlaying: false,
     isAccessibleOutputPlaying: false,
diff --git a/common/types/index.ts b/common/types/index.ts
new file mode 100644
index 0000000000..b45c30b26e
--- /dev/null
+++ b/common/types/index.ts
@@ -0,0 +1,33 @@
+// This file declares shared types between the client & server
+// Types should be defined in their own portions of the codebase and exported here.
+
+// SERVER SHARED TYPES:
+export type {
+  SanitisedApiKey,
+  IApiKey as ApiKey,
+  ApiKeyResponseOrError,
+  ApiKeyResponse,
+  CreateApiKeyRequestBody,
+  RemoveApiKeyRequestParams
+} from '../../server/types/apiKey';
+
+export * from '../../server/types/email';
+
+export type { Error, GenericResponseBody } from '../../server/types/express';
+
+export type {
+  User,
+  PublicUser,
+  PublicUserOrError,
+  PublicUserOrErrorOrGeneric,
+  UpdateSettingsRequestBody,
+  UnlinkThirdPartyResponseBody,
+  ResetPasswordInitiateRequestBody,
+  ResetOrUpdatePasswordRequestParams,
+  UpdatePasswordRequestBody,
+  CreateUserRequestBody,
+  DuplicateUserCheckQuery,
+  VerifyEmailQuery
+} from '../../server/types/user';
+
+export * from '../../server/types/userPreferences';