diff --git a/package.json b/package.json
index 819a2b8..af15912 100644
--- a/package.json
+++ b/package.json
@@ -23,7 +23,9 @@
     "@jixun/libparakeet": "0.1.1",
     "@reduxjs/toolkit": "^1.9.5",
     "framer-motion": "^10.12.16",
+    "immer": "^10.0.2",
     "nanoid": "^4.0.2",
+    "radash": "^10.8.1",
     "react": "^18.2.0",
     "react-dom": "^18.2.0",
     "react-dropzone": "^14.2.3",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 0fa7b36..29dfd3c 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -22,9 +22,15 @@ dependencies:
   framer-motion:
     specifier: ^10.12.16
     version: 10.12.16(react-dom@18.2.0)(react@18.2.0)
+  immer:
+    specifier: ^10.0.2
+    version: 10.0.2
   nanoid:
     specifier: ^4.0.2
     version: 4.0.2
+  radash:
+    specifier: ^10.8.1
+    version: 10.8.1
   react:
     specifier: ^18.2.0
     version: 18.2.0
@@ -5483,6 +5489,11 @@ packages:
     engines: { node: '>= 4' }
     dev: true
 
+  /immer@10.0.2:
+    resolution:
+      { integrity: sha512-Rx3CqeqQ19sxUtYV9CU911Vhy8/721wRFnJv3REVGWUmoAcIwzifTsdmJte/MV+0/XpM35LZdQMBGkRIoLPwQA== }
+    dev: false
+
   /immer@9.0.21:
     resolution:
       { integrity: sha512-bc4NBHqOqSfRW7POMkHd51LvClaeMXpm8dx0e8oE2GORbq5aRK7Bxl4FyzVLdGtLmvLKL7BTDBG5ACQm4HWjTA== }
@@ -6608,6 +6619,12 @@ packages:
       { integrity: sha512-NuaNSa6flKT5JaSYQzJok04JzTL1CA6aGhv5rfLW3PgqA+M2ChpZQnAC8h8i4ZFkBS8X5RqkDBHA7r4hej3K9A== }
     dev: true
 
+  /radash@10.8.1:
+    resolution:
+      { integrity: sha512-NzYo3XgM9Tzjf5iFPIMG2l5+LSOCi2H7Axe3Ry/1PrhlvuqxUoiLsmcTBtw4CfKtzy5Fzo79STiEj9JZWMfDQg== }
+    engines: { node: '>=14.18.0' }
+    dev: false
+
   /randombytes@2.1.0:
     resolution:
       { integrity: sha512-vYl3iOX+4CKUWuxGi9Ukhie6fsqXqS9FE2Zaic4tNFD2N2QQaXOMFbuKK4QmDHC0JO6B1Zp41J0LpT0oR68amQ== }
diff --git a/src/Loader.tsx b/src/Loader.tsx
new file mode 100644
index 0000000..a728531
--- /dev/null
+++ b/src/Loader.tsx
@@ -0,0 +1,24 @@
+import React, { useEffect } from 'react';
+import App from './App';
+
+import { ChakraProvider } from '@chakra-ui/react';
+import { Provider } from 'react-redux';
+import { theme } from './theme';
+import { persistSettings } from './features/settings/persistSettings';
+import type { AppStore } from './store';
+
+export function Loader({ store }: { store: AppStore }) {
+  useEffect(() => {
+    return persistSettings(store);
+  }, [store]);
+
+  return (
+    <React.StrictMode>
+      <ChakraProvider theme={theme}>
+        <Provider store={store}>
+          <App />
+        </Provider>
+      </ChakraProvider>
+    </React.StrictMode>
+  );
+}
diff --git a/src/features/settings/persistSettings.ts b/src/features/settings/persistSettings.ts
new file mode 100644
index 0000000..420266b
--- /dev/null
+++ b/src/features/settings/persistSettings.ts
@@ -0,0 +1,45 @@
+import { debounce } from 'radash';
+import { produce } from 'immer';
+
+import type { AppStore } from '~/store';
+import { SettingsState, settingsSlice, updateSettings } from './settingsSlice';
+import { enumObject } from '~/util/objects';
+import { getLogger } from '~/util/logUtils';
+
+const DEFAULT_STORAGE_KEY = 'um-react-settings';
+
+function mergeSettings(settings: SettingsState): SettingsState {
+  return produce(settingsSlice.getInitialState(), (draft) => {
+    for (const [k, v] of enumObject(settings.qmc2?.keys)) {
+      if (typeof v === 'string') {
+        draft.qmc2.keys[k] = v;
+      }
+    }
+  });
+}
+
+export function persistSettings(store: AppStore, storageKey = DEFAULT_STORAGE_KEY) {
+  let lastSettings: unknown;
+
+  try {
+    const loadedSettings: SettingsState = JSON.parse(localStorage.getItem(storageKey) ?? '');
+    if (loadedSettings) {
+      const mergedSettings = mergeSettings(loadedSettings);
+      store.dispatch(updateSettings(mergedSettings));
+      getLogger().debug('settings loaded');
+    }
+  } catch {
+    // load failed, ignore.
+  }
+
+  return store.subscribe(
+    debounce({ delay: 150 }, () => {
+      const currentSettings = store.getState().settings;
+      if (lastSettings !== currentSettings) {
+        lastSettings = currentSettings;
+        localStorage.setItem(storageKey, JSON.stringify(currentSettings));
+        getLogger().debug('settings saved');
+      }
+    })
+  );
+}
diff --git a/src/features/settings/settingsSlice.ts b/src/features/settings/settingsSlice.ts
new file mode 100644
index 0000000..b08a340
--- /dev/null
+++ b/src/features/settings/settingsSlice.ts
@@ -0,0 +1,31 @@
+import { createSlice } from '@reduxjs/toolkit';
+import type { PayloadAction } from '@reduxjs/toolkit';
+
+export interface QMCSettings {
+  keys: Record<string, string>; // {  [fileName]: ekey  }
+}
+
+export interface SettingsState {
+  qmc2: QMCSettings;
+}
+
+const initialState: SettingsState = {
+  qmc2: { keys: {} },
+};
+
+export const settingsSlice = createSlice({
+  name: 'settings',
+  initialState,
+  reducers: {
+    updateSettings: (_state, { payload }: PayloadAction<SettingsState>) => {
+      return payload;
+    },
+    resetConfig: () => {
+      return initialState;
+    },
+  },
+});
+
+export const { updateSettings, resetConfig } = settingsSlice.actions;
+
+export default settingsSlice.reducer;
diff --git a/src/main.tsx b/src/main.tsx
index dad48ae..469e6dc 100644
--- a/src/main.tsx
+++ b/src/main.tsx
@@ -1,21 +1,9 @@
-import React from 'react';
 import ReactDOM from 'react-dom/client';
-import App from './App';
 
-import { ChakraProvider } from '@chakra-ui/react';
-import { Provider } from 'react-redux';
 import { setupStore } from './store';
-import { theme } from './theme';
+import { Loader } from './Loader';
 
 // Private to this file only.
 const store = setupStore();
 
-ReactDOM.createRoot(document.getElementById('root') as HTMLElement).render(
-  <React.StrictMode>
-    <ChakraProvider theme={theme}>
-      <Provider store={store}>
-        <App />
-      </Provider>
-    </ChakraProvider>
-  </React.StrictMode>
-);
+ReactDOM.createRoot(document.getElementById('root') as HTMLElement).render(<Loader store={store} />);
diff --git a/src/store.ts b/src/store.ts
index 542db54..b97f8a6 100644
--- a/src/store.ts
+++ b/src/store.ts
@@ -1,8 +1,10 @@
 import { PreloadedState, combineReducers, configureStore } from '@reduxjs/toolkit';
 import fileListingReducer from './features/file-listing/fileListingSlice';
+import settingsReducer from './features/settings/settingsSlice';
 
 const rootReducer = combineReducers({
   fileListing: fileListingReducer,
+  settings: settingsReducer,
 });
 
 export const setupStore = (preloadedState?: PreloadedState<RootState>) =>
diff --git a/src/util/logUtils.ts b/src/util/logUtils.ts
index e37609a..29430b5 100644
--- a/src/util/logUtils.ts
+++ b/src/util/logUtils.ts
@@ -23,3 +23,23 @@ export function withGroupedLogs<R = unknown>(label: string, fn: () => R): R {
     );
   }
 }
+
+const noop = (..._args: unknown[]) => {
+  // noop
+};
+
+const dummyLogger = {
+  log: noop,
+  info: noop,
+  warn: noop,
+  debug: noop,
+  trace: noop,
+};
+
+export function getLogger() {
+  if (import.meta.env.ENABLE_PERF_LOG === '1') {
+    return window.console;
+  } else {
+    return dummyLogger;
+  }
+}
diff --git a/src/util/objects.ts b/src/util/objects.ts
new file mode 100644
index 0000000..77f700b
--- /dev/null
+++ b/src/util/objects.ts
@@ -0,0 +1,7 @@
+export function* enumObject<T>(obj: Record<string, T> | null | void): Generator<[string, T]> {
+  if (obj && typeof obj === 'object') {
+    for (const key in obj) {
+      yield [key, obj[key]];
+    }
+  }
+}