diff --git a/dist/styles.css b/dist/styles.css
index 2b382da..960c9eb 100644
--- a/dist/styles.css
+++ b/dist/styles.css
@@ -75,6 +75,10 @@ body {
     background: #a4262c;
     border-color: #a4262c;
 }
+.ms-Button--primary.danger.is-disabled {
+    background: var(--neutralLighter);
+    border-color: var(--neutralLighter);
+}
 .ms-Button--commandBar.active {
     background-color: var(--neutralLight);
     color: var(--neutralDark);
@@ -326,6 +330,11 @@ img.favicon {
     font-size: 12px;
     color: var(--neutralSecondary);
 }
+.settings-hint.up {
+    position: relative;
+    top: -12px;
+    line-height: unset;
+}
 .settings-about {
     margin: 72px 0;
     color: var(--black);
@@ -543,6 +552,15 @@ img.favicon {
 .flex-fix {
     min-width: 280px;
 }
+.cards-feed-container > .empty, .list-feed > .empty {
+    width: 100%;
+    height: calc(100vh - 64px);
+    display: flex;
+    justify-content: space-around;
+    align-items: center;
+    color: var(--neutralSecondary);
+    font-size: 14px;
+}
 
 .info {
     position: relative;
diff --git a/items b/items
new file mode 100644
index 0000000..43f72db
--- /dev/null
+++ b/items
@@ -0,0 +1 @@
+{"$$indexCreated":{"fieldName":"source","unique":false,"sparse":false}}
diff --git a/package.json b/package.json
index 636f9f4..a20c7d3 100644
--- a/package.json
+++ b/package.json
@@ -22,8 +22,7 @@
       "output": "./bin/${platform}/${arch}/"
     },
     "win": {
-      "target": [ "nsis", "appx" ],
-      "certificateFile": "./bin/key.pfx"
+      "target": [ "nsis", "appx" ]
     },
     "appx": {
       "applicationId": "FluentReader",
diff --git a/sources b/sources
new file mode 100644
index 0000000..308ddbf
--- /dev/null
+++ b/sources
@@ -0,0 +1,2 @@
+{"$$indexCreated":{"fieldName":"sid","unique":true,"sparse":false}}
+{"$$indexCreated":{"fieldName":"url","unique":true,"sparse":false}}
diff --git a/src/components/feeds/cards-feed.tsx b/src/components/feeds/cards-feed.tsx
index 292ce82..bff03ea 100644
--- a/src/components/feeds/cards-feed.tsx
+++ b/src/components/feeds/cards-feed.tsx
@@ -53,6 +53,9 @@ class CardsFeed extends React.Component<FeedProps> {
                         onClick={() => this.props.loadMore(this.props.feed)} /></div>
                     : null
                 }
+                { this.props.items.length === 0 && (
+                    <div className="empty">{intl.get("article.empty")}</div>
+                )}
             </div>
         )
     }
diff --git a/src/components/feeds/list-feed.tsx b/src/components/feeds/list-feed.tsx
index 23baca7..64e4054 100644
--- a/src/components/feeds/list-feed.tsx
+++ b/src/components/feeds/list-feed.tsx
@@ -28,6 +28,9 @@ class ListFeed extends React.Component<FeedProps> {
                         onClick={() => this.props.loadMore(this.props.feed)} /></div>
                     : null
                 }
+                { this.props.items.length === 0 && (
+                    <div className="empty">{intl.get("article.empty")}</div>
+                )}
             </div>
         )
     }
diff --git a/src/components/settings/app.tsx b/src/components/settings/app.tsx
index 24ccfe0..9f08d22 100644
--- a/src/components/settings/app.tsx
+++ b/src/components/settings/app.tsx
@@ -1,19 +1,56 @@
 import * as React from "react"
 import intl = require("react-intl-universal")
-import { urlTest } from "../../scripts/utils"
+import { urlTest, byteToMB, calculateItemSize } from "../../scripts/utils"
 import { getProxy, getProxyStatus, toggleProxyStatus, setProxy, getThemeSettings, setThemeSettings, ThemeSettings, getLocaleSettings, exportAll } from "../../scripts/settings"
 import { Stack, Label, Toggle, TextField, DefaultButton, ChoiceGroup, IChoiceGroupOption, loadTheme, Dropdown, IDropdownOption, PrimaryButton } from "@fluentui/react"
 import { remote } from "electron"
+import DangerButton from "../utils/danger-button"
 
 type AppTabProps = {
     setLanguage: (option: string) => void
+    deleteArticles: (days: number) => Promise<void>
+    importAll: () => void
 }
 
-class AppTab extends React.Component<AppTabProps> {
-    state = {
-        pacStatus: getProxyStatus(),
-        pacUrl: getProxy(),
-        themeSettings: getThemeSettings()
+type AppTabState = {
+    pacStatus: boolean
+    pacUrl: string
+    themeSettings: ThemeSettings
+    itemSize: string
+    cacheSize: string
+    deleteIndex: string
+}
+
+class AppTab extends React.Component<AppTabProps, AppTabState> {
+    constructor(props) {
+        super(props)
+        this.state = {
+            pacStatus: getProxyStatus(),
+            pacUrl: getProxy(),
+            themeSettings: getThemeSettings(),
+            itemSize: null,
+            cacheSize: null,
+            deleteIndex: null
+        }
+        this.getItemSize()
+        this.getCacheSize()
+    }
+
+    getCacheSize = () => {
+        remote.session.defaultSession.getCacheSize().then(size => {
+            this.setState({ cacheSize: byteToMB(size) })
+        })
+    }
+    getItemSize = () => {
+        calculateItemSize().then((size) => {
+            this.setState({ itemSize: byteToMB(size) })
+        })
+    }
+
+    clearCache = () => {
+        remote.session.defaultSession.clearCache().then(() => {
+            this.getCacheSize()
+        })
     }
     
     themeChoices = (): IChoiceGroupOption[] => [
@@ -22,6 +59,24 @@ class AppTab extends React.Component<AppTabProps> {
         { key: ThemeSettings.Dark, text: intl.get("app.darkTheme") }
     ]
 
+    deleteOptions = (): IDropdownOption[] => [
+        { key: "7", text: intl.get("app.daysAgo", { days: 7 }) },
+        { key: "14", text: intl.get("app.daysAgo", { days: 14 }) },
+        { key: "21", text: intl.get("app.daysAgo", { days: 21 }) },
+        { key: "28", text: intl.get("app.daysAgo", { days: 28 }) },
+        { key: "0", text: intl.get("app.deleteAll") },
+    ]
+
+    deleteChange = (_, item: IDropdownOption) => {
+        this.setState({ deleteIndex: item ? String(item.key) : null })
+    }
+
+    confirmDelete = () => {
+        this.setState({ itemSize: null })
+        this.props.deleteArticles(parseInt(this.state.deleteIndex))
+            .then(() => this.getItemSize())
+    }
+
     languageOptions = (): IDropdownOption[] => [
         { key: "default", text: intl.get("followSystem") },
         { key: "en-US", text: "English" },
@@ -38,6 +93,7 @@ class AppTab extends React.Component<AppTabProps> {
     
     handleInputChange = (event) => {
         const name: string = event.target.name
+        // @ts-ignore
         this.setState({[name]: event.target.value.trim()})
     }
 
@@ -48,7 +104,7 @@ class AppTab extends React.Component<AppTabProps> {
 
     onThemeChange = (_, option: IChoiceGroupOption) => {
         setThemeSettings(option.key as ThemeSettings)
-        this.setState({ themeSettings: option.key })
+        this.setState({ themeSettings: option.key as ThemeSettings })
     }
 
     exportAll = () => {
@@ -110,13 +166,44 @@ class AppTab extends React.Component<AppTabProps> {
                 </Stack>
             </form>}
 
+            <Label>{intl.get("app.cleanup")}</Label>
+            <Stack horizontal>
+                <Stack.Item grow>
+                    <Dropdown 
+                        placeholder={intl.get("app.deleteChoices")} 
+                        options={this.deleteOptions()}
+                        selectedKey={this.state.deleteIndex}
+                        onChange={this.deleteChange} />
+                </Stack.Item>
+                <Stack.Item>
+                    <DangerButton 
+                        disabled={this.state.itemSize === null || this.state.deleteIndex === null}
+                        text={intl.get("app.confirmDelete")}
+                        onClick={this.confirmDelete} />
+                </Stack.Item>
+            </Stack>
+            <span className="settings-hint up">
+                {this.state.itemSize ? intl.get("app.itemSize", {size: this.state.itemSize}) : intl.get("app.calculatingSize")}
+            </span>
+            <Stack horizontal>
+                <Stack.Item>
+                    <DefaultButton
+                        text={intl.get("app.cache")}
+                        disabled={this.state.cacheSize === null || this.state.cacheSize === "0MB"}
+                        onClick={this.clearCache} />
+                </Stack.Item>
+            </Stack>
+            <span className="settings-hint up">
+                {this.state.cacheSize ? intl.get("app.cacheSize", {size: this.state.cacheSize}) : intl.get("app.calculatingSize")}
+            </span>
+
             <Label>{intl.get("app.data")}</Label>
             <Stack horizontal>
             <Stack.Item>
                     <PrimaryButton onClick={this.exportAll} text={intl.get("app.backup")} />
                 </Stack.Item>
                 <Stack.Item>
-                    <DefaultButton text={intl.get("app.restore")} />
+                    <DefaultButton onClick={this.props.importAll} text={intl.get("app.restore")} />
                 </Stack.Item>
             </Stack>
         </div>
diff --git a/src/components/utils/danger-button.tsx b/src/components/utils/danger-button.tsx
index 1846aea..4bcd1d1 100644
--- a/src/components/utils/danger-button.tsx
+++ b/src/components/utils/danger-button.tsx
@@ -15,15 +15,17 @@ class DangerButton extends PrimaryButton {
     }
 
     onClick = (event: React.MouseEvent<HTMLButtonElement>) => {
-        if (this.state.confirming) {
-            if (this.props.onClick) this.props.onClick(event)
-            clearTimeout(this.timerID)
-            this.clear()
-        } else {
-            this.setState({ confirming: true })
-            this.timerID = setTimeout(() => {
+        if (!this.props.disabled) {
+            if (this.state.confirming) {
+                if (this.props.onClick) this.props.onClick(event)
+                clearTimeout(this.timerID)
                 this.clear()
-            }, 5000)
+            } else {
+                this.setState({ confirming: true })
+                this.timerID = setTimeout(() => {
+                    this.clear()
+                }, 5000)
+            }
         }
     }
 
diff --git a/src/containers/settings/app-container.tsx b/src/containers/settings/app-container.tsx
index fb0064d..702bd2c 100644
--- a/src/containers/settings/app-container.tsx
+++ b/src/containers/settings/app-container.tsx
@@ -1,12 +1,51 @@
+import intl = require("react-intl-universal")
 import { connect } from "react-redux"
-import { setLocaleSettings } from "../../scripts/settings"
-import { initIntl } from "../../scripts/models/app"
+import { setLocaleSettings, importAll } from "../../scripts/settings"
+import { initIntl, saveSettings } from "../../scripts/models/app"
+import * as db from "../../scripts/db"
 import AppTab from "../../components/settings/app"
+import { initFeeds } from "../../scripts/models/feed"
+import { remote } from "electron"
 
 const mapDispatchToProps = dispatch => ({
     setLanguage: (option: string) => {
         setLocaleSettings(option)
         dispatch(initIntl())
+    },
+    deleteArticles: (days: number) => new Promise((resolve) => {
+        dispatch(saveSettings())
+        let date = new Date()
+        date.setTime(date.getTime() - days * 86400000)
+        db.idb.remove({ date: { $lt: date } }, { multi: true }, () => {
+            dispatch(initFeeds(true)).then(() => dispatch(saveSettings()))
+            db.idb.prependOnceListener("compaction.done", () => {
+                resolve()
+            })
+            db.idb.persistence.compactDatafile()
+        })
+    }),
+    importAll: () => {
+        let window = remote.getCurrentWindow()
+        remote.dialog.showOpenDialog(window, {
+            filters: [{ name: intl.get("app.frData"), extensions: ["frdata"] }],
+            properties: ["openFile"]
+        }).then(result => {
+            if (!result.canceled) {
+                remote.dialog.showMessageBox(remote.getCurrentWindow(), {
+                    type: "warning",
+                    title: intl.get("app.restore"),
+                    message: intl.get("app.confirmImport"),
+                    buttons: process.platform === "win32" ? ["Yes", "No"] : [intl.get("confirm"), intl.get("cancel")],
+                    defaultId: 1,
+                    cancelId: 1
+                }).then(response => {
+                    if (response.response === 0) {
+                        dispatch(saveSettings())
+                        importAll(result.filePaths[0])
+                    }
+                })
+            }
+        })
     }
 })
 
diff --git a/src/electron.ts b/src/electron.ts
index 9a4a6b9..563bcf7 100644
--- a/src/electron.ts
+++ b/src/electron.ts
@@ -3,7 +3,8 @@ import windowStateKeeper = require("electron-window-state")
 import Store = require("electron-store")
 
 let mainWindow: BrowserWindow
-const store = new Store()
+let store = new Store()
+let restarting = false
 nativeTheme.themeSource = store.get("theme", "system")
 
 function createWindow() {
@@ -31,28 +32,38 @@ function createWindow() {
         }
     })
     mainWindowState.manage(mainWindow)
-    mainWindow.on('ready-to-show', () => {
+    mainWindow.on("ready-to-show", () => {
         mainWindow.show()
         mainWindow.focus()
         mainWindow.webContents.openDevTools()
     });
     // and load the index.html of the app.
-    mainWindow.loadFile((app.isPackaged ? "dist/" : "") + 'index.html')
+    mainWindow.loadFile((app.isPackaged ? "dist/" : "") + "index.html")
 }
 
 Menu.setApplicationMenu(null)
 
-app.on('ready', createWindow)
+app.on("ready", createWindow)
 
-app.on('window-all-closed', function () {
+app.on("window-all-closed", function () {
     mainWindow = null
-    if (process.platform !== 'darwin') {
+    if (restarting) {
+        restarting = false
+        store = new Store()
+        nativeTheme.themeSource = store.get("theme", "system")
+        createWindow()
+    } else if (process.platform !== "darwin") {
         app.quit()
     }
 })
 
-app.on('activate', function () {
+app.on("activate", function () {
     if (mainWindow === null) {
         createWindow()
     }
 })
+
+ipcMain.on("restart", () => {
+    restarting = true
+    mainWindow.close()
+})
diff --git a/src/scripts/config-schema.ts b/src/scripts/config-schema.ts
index 05d3ff4..29ced55 100644
--- a/src/scripts/config-schema.ts
+++ b/src/scripts/config-schema.ts
@@ -12,6 +12,7 @@ import { SourceGroup } from "./models/group"
 } */
 
 export type schemaTypes = {
+    version: string
     theme: ThemeSettings
     pac: string
     pacOn: boolean
diff --git a/src/scripts/i18n/en-US.json b/src/scripts/i18n/en-US.json
index 16b3484..1fc7658 100644
--- a/src/scripts/i18n/en-US.json
+++ b/src/scripts/i18n/en-US.json
@@ -35,6 +35,7 @@
         "subscriptions": "Subscriptions"
     },
     "article": {
+        "empty": "No articles",
         "untitled": "(Untitled)",
         "hide": "Hide article",
         "unhide": "Unhide article",
@@ -112,6 +113,16 @@
         "groupHint": "Double click on group to edit sources. Drag and drop to reorder."
     },
     "app": {
+        "cleanup": "Clean up",
+        "cache": "Clear cache",
+        "cacheSize": "Cached {size} of data",
+        "deleteChoices": "Delete articles from ... days ago",
+        "confirmDelete": "Delete",
+        "daysAgo": "{days} days ago",
+        "deleteAll": "Delete all articles",
+        "calculatingSize": "Calculating size...",
+        "itemSize": "Around {size} of local storage is occupied by articles",
+        "confirmImport": "Do you really want to import data from the backup file? All current data will be wiped.",
         "data": "Application Data",
         "backup": "Backup",
         "restore": "Restore",
diff --git a/src/scripts/i18n/zh-CN.json b/src/scripts/i18n/zh-CN.json
index 5db08fe..8fd44b7 100644
--- a/src/scripts/i18n/zh-CN.json
+++ b/src/scripts/i18n/zh-CN.json
@@ -35,6 +35,7 @@
         "subscriptions": "订阅源"
     },
     "article": {
+        "empty": "无文章",
         "untitled": "（无标题）",
         "hide": "隐藏文章",
         "unhide": "取消隐藏",
@@ -112,6 +113,16 @@
         "groupHint": "双击分组以修改订阅源，可通过拖拽排序"
     },
     "app": {
+        "cleanup": "清理",
+        "cache": "清空缓存",
+        "cacheSize": "已缓存{size}数据",
+        "deleteChoices": "删除 … 天前的文章",
+        "confirmDelete": "删除文章",
+        "daysAgo": "{days}天前",
+        "deleteAll": "删除全部文章",
+        "calculatingSize": "正在计算占用空间…",
+        "itemSize": "本地文章约占用{size}空间",
+        "confirmImport": "确认要从备份文件导入数据吗？这将清除所有应用数据。",
         "data": "应用数据",
         "backup": "备份",
         "restore": "还原",
diff --git a/src/scripts/models/app.ts b/src/scripts/models/app.ts
index d722179..9b2dfd2 100644
--- a/src/scripts/models/app.ts
+++ b/src/scripts/models/app.ts
@@ -7,6 +7,7 @@ import { SourceGroupActionTypes, UPDATE_SOURCE_GROUP, ADD_SOURCE_TO_GROUP, DELET
 import { PageActionTypes, SELECT_PAGE, PageType, selectAllArticles } from "./page"
 import { getCurrentLocale } from "../settings"
 import locales from "../i18n/_locales"
+import * as db from "../db"
 
 export enum ContextMenuType {
     Hidden, Item, Text, View, Group
@@ -198,7 +199,10 @@ export function initApp(): AppThunk {
             dispatch(initFeeds())
         ).then(() => {
             dispatch(selectAllArticles())
-            dispatch(fetchItems())
+            return dispatch(fetchItems())
+        }).then(() => {
+            db.sdb.persistence.compactDatafile()
+            db.idb.persistence.compactDatafile()
         })
     }
 }
diff --git a/src/scripts/models/item.ts b/src/scripts/models/item.ts
index 9af9e2e..3c312e8 100644
--- a/src/scripts/models/item.ts
+++ b/src/scripts/models/item.ts
@@ -26,16 +26,6 @@ export class RSSItem {
         this.link = item.link || ""
         this.fetchedDate = new Date()
         this.date = item.isoDate ? new Date(item.isoDate) : this.fetchedDate
-        if (item.thumb) this.thumb = item.thumb
-        else if (item.image) this.thumb = item.image
-        else {
-            let dom = domParser.parseFromString(item.content, "text/html")
-            let baseEl = dom.createElement('base')
-            baseEl.setAttribute('href', this.link.split("/").slice(0, 3).join("/"))
-            dom.head.append(baseEl)
-            let img = dom.querySelector("img")
-            if (img && img.src) this.thumb = img.src
-        }
         if (item.fullContent) {
             this.content = item.fullContent
             this.snippet = htmlDecode(item.fullContent)
@@ -43,6 +33,16 @@ export class RSSItem {
             this.content = item.content || ""
             this.snippet = htmlDecode(item.contentSnippet || "")
         }
+        if (item.thumb) this.thumb = item.thumb
+        else if (item.image) this.thumb = item.image
+        else {
+            let dom = domParser.parseFromString(this.content, "text/html")
+            let baseEl = dom.createElement('base')
+            baseEl.setAttribute('href', this.link.split("/").slice(0, 3).join("/"))
+            dom.head.append(baseEl)
+            let img = dom.querySelector("img")
+            if (img && img.src) this.thumb = img.src
+        }
         this.creator = item.creator
         this.hasRead = false
     }
diff --git a/src/scripts/settings.ts b/src/scripts/settings.ts
index faea277..2015714 100644
--- a/src/scripts/settings.ts
+++ b/src/scripts/settings.ts
@@ -1,6 +1,6 @@
 import { remote, ipcRenderer } from "electron"
 import { ViewType } from "./models/page"
-import { IPartialTheme, loadTheme } from "@fluentui/react"
+import { IPartialTheme, loadTheme, values } from "@fluentui/react"
 import locales from "./i18n/_locales"
 import Store = require("electron-store")
 import { schemaTypes } from "./config-schema"
@@ -109,7 +109,7 @@ export function getCurrentLocale() {
     return (locale in locales) ? locale : "en-US"
 }
 
-export function exportAll(path) {
+export function exportAll(path: string) {
     let output = {}
     for (let [key, value] of store) {
         output[key] = value
@@ -132,4 +132,35 @@ export function exportAll(path) {
             }
         }
     }
-}
\ No newline at end of file
+}
+
+export function importAll(path) {
+    fs.readFile(path, "utf-8", async (err, data) => {
+        if (err) {
+            console.log(err)
+        } else {
+            let configs = JSON.parse(data)
+            let openRequest = window.indexedDB.open("NeDB")
+            openRequest.onsuccess = () => {
+                let db = openRequest.result
+                let objectStore = db.transaction("nedbdata", "readwrite").objectStore("nedbdata")
+                let requests = Object.entries(configs.nedb).map(([key, value]) => {
+                    return objectStore.put(value, key)
+                })
+                let promises = requests.map(req => new Promise((resolve, reject) => {
+                    req.onsuccess = () => resolve()
+                    req.onerror = () => reject()
+                }))
+                Promise.all(promises).then(() => {
+                    delete configs.nedb
+                    store.clear()
+                    for (let [key, value] of Object.entries(configs)) {
+                        // @ts-ignore
+                        store.set(key, value)
+                    }
+                    ipcRenderer.send("restart")
+                })
+            }
+        }
+    })
+}
diff --git a/src/scripts/update-scripts.ts b/src/scripts/update-scripts.ts
new file mode 100644
index 0000000..bcd94c5
--- /dev/null
+++ b/src/scripts/update-scripts.ts
@@ -0,0 +1,11 @@
+import { app } from "electron"
+import Store = require("electron-store")
+
+export default function performUpdate(store: Store) {
+    let version = store.get("version", null)
+    let currentVersion = app.getVersion()
+
+    if (version != currentVersion) {
+        store.set("version", currentVersion)
+    }
+}
\ No newline at end of file
diff --git a/src/scripts/utils.ts b/src/scripts/utils.ts
index 2694a56..e0db184 100644
--- a/src/scripts/utils.ts
+++ b/src/scripts/utils.ts
@@ -84,4 +84,26 @@ export function mergeSortedArrays<T>(a: T[], b: T[], cmp: ((x: T, y: T) => numbe
     while (i < a.length) merged.push(a[i++])
     while (j < b.length) merged.push(b[j++])
     return merged
+}
+
+export function byteToMB(B: number) {
+    let MB = Math.round(B / 1048576)
+    return MB + "MB"
+}
+
+export function calculateItemSize(): Promise<number> {
+    return new Promise((resolve, reject) => {
+        let openRequest = window.indexedDB.open("NeDB")
+        openRequest.onsuccess = () => {
+            let db = openRequest.result
+            let objectStore = db.transaction("nedbdata").objectStore("nedbdata")
+            let getRequest = objectStore.get("items")
+            getRequest.onsuccess = () => {
+                let resultBuffer = Buffer.from(getRequest.result)
+                resolve(resultBuffer.length)
+            }
+            getRequest.onerror = () => reject()
+        }
+        openRequest.onerror = () => reject()
+    })
 }
\ No newline at end of file
diff --git a/webpack.config.js b/webpack.config.js
index 0ba253e..b993195 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -2,7 +2,7 @@ const HtmlWebpackPlugin = require('html-webpack-plugin');
 
 module.exports = [
   {
-    mode: 'development',
+    mode: 'production',
     entry: './src/electron.ts',
     target: 'electron-main',
     module: {