diff --git a/dist/styles/main.css b/dist/styles/main.css
index aa38e44..c338a8e 100644
--- a/dist/styles/main.css
+++ b/dist/styles/main.css
@@ -154,6 +154,12 @@ img.favicon.dropdown {
 .settings-rules-icons i:last-of-type {
     color: var(--neutralSecondary);
 }
+.login-form {
+    width: 300px;
+}
+.login-form .ms-Label {
+    width: 72px;
+}
 
 .main {
     margin-top: calc(-1 * var(--navHeight));
diff --git a/package-lock.json b/package-lock.json
index 7514e5b..b21a718 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -2614,9 +2614,9 @@
       }
     },
     "elliptic": {
-      "version": "6.5.2",
-      "resolved": "https://registry.npmjs.org/elliptic/-/elliptic-6.5.2.tgz",
-      "integrity": "sha512-f4x70okzZbIQl/NSRLkI/+tteV/9WqL98zx+SQ69KbXxmVrmjwsNUPn/gYJJ0sHvEak24cZgHIPegRePAtA/xw==",
+      "version": "6.5.3",
+      "resolved": "https://registry.npmjs.org/elliptic/-/elliptic-6.5.3.tgz",
+      "integrity": "sha512-IMqzv5wNQf+E6aHeIqATs0tOLeOTwj1QKbRcS3jBbYkl5oLAserA8yJTT7/VyHUYG91PRmPyeQDObKLPpeS4dw==",
       "dev": true,
       "requires": {
         "bn.js": "^4.4.0",
@@ -4058,6 +4058,12 @@
         }
       }
     },
+    "js-md5": {
+      "version": "0.7.3",
+      "resolved": "https://registry.npmjs.org/js-md5/-/js-md5-0.7.3.tgz",
+      "integrity": "sha512-ZC41vPSTLKGwIRjqDh8DfXoCrdQIyBgspJVPXHBGu4nZlAEvG3nf+jO9avM9RmLiGakg7vz974ms99nEV0tmTQ==",
+      "dev": true
+    },
     "js-tokens": {
       "version": "4.0.0",
       "resolved": "https://registry.npmjs.org/js-tokens/-/js-tokens-4.0.0.tgz",
diff --git a/package.json b/package.json
index 8620b3c..118326f 100644
--- a/package.json
+++ b/package.json
@@ -96,6 +96,7 @@
     "electron-window-state": "^5.0.3",
     "hard-source-webpack-plugin": "^0.13.1",
     "html-webpack-plugin": "^4.3.0",
+    "js-md5": "^0.7.3",
     "nedb": "^1.8.0",
     "qrcode.react": "^1.0.0",
     "react": "^16.13.1",
diff --git a/src/components/nav.tsx b/src/components/nav.tsx
index 6011be8..0580822 100644
--- a/src/components/nav.tsx
+++ b/src/components/nav.tsx
@@ -82,7 +82,8 @@ class Nav extends React.Component<NavProps, NavState> {
         window.utils.closeWindow()
     }
 
-    canFetch = () => this.props.state.sourceInit && this.props.state.feedInit && !this.props.state.fetchingItems
+    canFetch = () => this.props.state.sourceInit && this.props.state.feedInit 
+        && !this.props.state.syncing && !this.props.state.fetchingItems
     fetching = () => !this.canFetch() ? " fetching" : ""
     menuOn = () => this.props.state.menu ? " menu-on" : ""
     itemOn = () => this.props.itemShown ? " item-on" : ""
diff --git a/src/components/settings/service.tsx b/src/components/settings/service.tsx
index 684c675..18643a7 100644
--- a/src/components/settings/service.tsx
+++ b/src/components/settings/service.tsx
@@ -2,9 +2,19 @@ import * as React from "react"
 import intl from "react-intl-universal"
 import { ServiceConfigs, SyncService } from "../../schema-types"
 import { Stack, Icon, Link, Dropdown, IDropdownOption } from "@fluentui/react"
+import FeverConfigsTab from "./services/fever"
 
-export type ServiceTabProps = {
+type ServiceTabProps = {
     configs: ServiceConfigs
+    save: (configs: ServiceConfigs) => void
+    sync: () => Promise<void>
+    remove: () => Promise<void>
+    blockActions: () => void
+    authenticate: (configs: ServiceConfigs) => Promise<boolean>
+}
+
+export type ServiceConfigsTabProps = ServiceTabProps & {
+    exit: () => void
 }
 
 type ServiceTabState = {
@@ -28,10 +38,14 @@ export class ServiceTab extends React.Component<ServiceTabProps, ServiceTabState
         if (option.key === -1) {
             window.utils.openExternal("https://github.com/yang991178/fluent-reader/issues/23")
         } else {
-
+            this.setState({ type: option.key as number })
         }
     }
 
+    exitConfigsTab = () => {
+        this.setState({ type: SyncService.None })
+    }
+
     render = () => (
         <div className="tab-body">
             {this.state.type === SyncService.None
@@ -58,7 +72,7 @@ export class ServiceTab extends React.Component<ServiceTabProps, ServiceTabState
                         style={{marginTop: 32, width: 180}} />
                 </Stack>
             )
-            : null}
+            : <FeverConfigsTab {...this.props} exit={this.exitConfigsTab} />}
         </div>
     )
 }
\ No newline at end of file
diff --git a/src/components/settings/services/fever.tsx b/src/components/settings/services/fever.tsx
new file mode 100644
index 0000000..036802c
--- /dev/null
+++ b/src/components/settings/services/fever.tsx
@@ -0,0 +1,185 @@
+import * as React from "react"
+import intl from "react-intl-universal"
+import md5 from "js-md5"
+import { ServiceConfigsTabProps } from "../service"
+import { FeverConfigs } from "../../../scripts/models/services/fever"
+import { SyncService } from "../../../schema-types"
+import { Stack, Icon, Label, TextField, PrimaryButton, DefaultButton, Checkbox, MessageBar, MessageBarType, Dropdown, IDropdownOption } from "@fluentui/react"
+import DangerButton from "../../utils/danger-button"
+import { urlTest } from "../../../scripts/utils"
+import { exists } from "fs"
+
+type FeverConfigsTabState = {
+    existing: boolean
+    endpoint: string
+    username: string
+    password: string
+    fetchLimit: number
+    importGroups: boolean
+}
+
+class FeverConfigsTab extends React.Component<ServiceConfigsTabProps, FeverConfigsTabState> {
+    constructor(props: ServiceConfigsTabProps) {
+        super(props)
+        const configs = props.configs as FeverConfigs
+        this.state = {
+            existing: configs.type === SyncService.Fever,
+            endpoint: configs.endpoint || "",
+            username: configs.username || "",
+            password: "",
+            fetchLimit: configs.fetchLimit || 250,
+            importGroups: true,
+        }
+    }
+
+    fetchLimitOptions = (): IDropdownOption[] => [
+        { key: 250, text: intl.get("service.fetchLimitNum", { count: 250 }) },
+        { key: 500, text: intl.get("service.fetchLimitNum", { count: 500 }) },
+        { key: 750, text: intl.get("service.fetchLimitNum", { count: 750 }) },
+        { key: 1000, text: intl.get("service.fetchLimitNum", { count: 1000 }) },
+    ]
+    onFetchLimitOptionChange = (_, option: IDropdownOption) => {
+        this.setState({ fetchLimit: option.key as number })
+    }
+
+    handleInputChange = (event) => {
+        const name: string = event.target.name
+        // @ts-expect-error
+        this.setState({[name]: event.target.value})
+    }
+
+    checkNotEmpty = (v: string) => {
+        return (!this.state.existing && v.length == 0) ? intl.get("emptyField") : ""
+    }
+
+    validateForm = () => {
+        return urlTest(this.state.endpoint.trim()) && (this.state.existing || (this.state.username && this.state.password))
+    }
+
+    save = async () => {
+        let configs: FeverConfigs
+        if (this.state.existing) {
+            configs = {
+                ...this.props.configs,
+                endpoint: this.state.endpoint,
+                fetchLimit: this.state.fetchLimit
+            } as FeverConfigs
+            if (this.state.password) 
+                configs.apiKey = md5(`${configs.username}:${this.state.password}`)
+        } else {
+            configs = {
+                type: SyncService.Fever,
+                endpoint: this.state.endpoint,
+                username: this.state.username,
+                fetchLimit: this.state.fetchLimit,
+                apiKey: md5(`${this.state.username}:${this.state.password}`)
+            }
+            if (this.state.importGroups) configs.importGroups = true
+        }
+        this.props.blockActions()
+        const valid = await this.props.authenticate(configs)
+        if (valid) {
+            this.props.save(configs)
+            this.setState({ existing: true })
+            this.props.sync()
+        } else {
+            this.props.blockActions()
+            window.utils.showErrorBox(intl.get("service.failure"), intl.get("service.failureHint"))
+        }
+    }
+
+    remove = async () => {
+        this.props.exit()
+        await this.props.remove()
+    }
+
+    render() {
+        return <>
+            <Stack tokens={{childrenGap: 8}}>
+                {!this.state.existing && (
+                    <MessageBar messageBarType={MessageBarType.warning}>{intl.get("service.overwriteWarning")}</MessageBar>
+                )}
+                {!this.state.existing && this.state.importGroups && (
+                    <MessageBar messageBarType={MessageBarType.info}>{intl.get("service.groupsWarning")}</MessageBar>
+                )}
+            </Stack>
+            <Stack horizontalAlign="center" style={{marginTop: 48}}>
+                <Icon iconName="Calories" style={{fontSize: 32, userSelect: "none"}} />
+                <Label style={{margin: "8px 0 36px"}}>Fever API</Label>
+                <Stack className="login-form" horizontal>
+                    <Stack.Item>
+                        <Label>{intl.get("service.endpoint")}</Label>
+                    </Stack.Item>
+                    <Stack.Item grow>
+                        <TextField
+                            onGetErrorMessage={v => urlTest(v.trim()) ? "" : intl.get("sources.badUrl")} 
+                            validateOnLoad={false}
+                            name="endpoint"
+                            value={this.state.endpoint}
+                            onChange={this.handleInputChange} />
+                    </Stack.Item>
+                </Stack>
+                <Stack className="login-form" horizontal>
+                    <Stack.Item>
+                        <Label>{intl.get("service.username")}</Label>
+                    </Stack.Item>
+                    <Stack.Item grow>
+                        <TextField
+                            disabled={this.state.existing}
+                            onGetErrorMessage={this.checkNotEmpty} 
+                            validateOnLoad={false}
+                            name="username"
+                            value={this.state.username}
+                            onChange={this.handleInputChange} />
+                    </Stack.Item>
+                </Stack>
+                <Stack className="login-form" horizontal>
+                    <Stack.Item>
+                        <Label>{intl.get("service.password")}</Label>
+                    </Stack.Item>
+                    <Stack.Item grow>
+                        <TextField
+                            type="password"
+                            placeholder={this.state.existing ? intl.get("service.unchanged") : ""}
+                            onGetErrorMessage={this.checkNotEmpty} 
+                            validateOnLoad={false}
+                            name="password"
+                            value={this.state.password}
+                            onChange={this.handleInputChange} />
+                    </Stack.Item>
+                </Stack>
+                <Stack className="login-form" horizontal>
+                    <Stack.Item>
+                        <Label>{intl.get("service.fetchLimit")}</Label>
+                    </Stack.Item>
+                    <Stack.Item grow>
+                        <Dropdown
+                            options={this.fetchLimitOptions()}
+                            selectedKey={this.state.fetchLimit}
+                            onChange={this.onFetchLimitOptionChange} />
+                    </Stack.Item>
+                </Stack>
+                {!this.state.existing && <Checkbox 
+                    label={intl.get("service.importGroups")} 
+                    checked={this.state.importGroups}
+                    onChange={(_, c) => this.setState({importGroups: c})} />}
+                <Stack horizontal style={{marginTop: 32}}>
+                    <Stack.Item>
+                        <PrimaryButton 
+                            disabled={!this.validateForm()}
+                            onClick={this.save}
+                            text={this.state.existing ? intl.get("edit") : intl.get("confirm")} />
+                    </Stack.Item>
+                    <Stack.Item>
+                        {this.state.existing 
+                            ? <DangerButton onClick={this.remove} text={intl.get("delete")} />
+                            : <DefaultButton onClick={this.props.exit} text={intl.get("cancel")} />
+                        }
+                    </Stack.Item>
+                </Stack>
+            </Stack>
+        </>
+    }
+}
+
+export default FeverConfigsTab
\ No newline at end of file
diff --git a/src/containers/settings-container.tsx b/src/containers/settings-container.tsx
index c4f18ee..aad26cd 100644
--- a/src/containers/settings-container.tsx
+++ b/src/containers/settings-container.tsx
@@ -10,7 +10,7 @@ const mapStateToProps = createSelector(
     [getApp],
     (app) => ({
     display: app.settings.display,
-    blocked: !app.sourceInit || app.fetchingItems || app.settings.saving,
+    blocked: !app.sourceInit || app.syncing || app.fetchingItems || app.settings.saving,
     exitting: app.settings.saving
 }))
 
diff --git a/src/containers/settings/service-container.tsx b/src/containers/settings/service-container.tsx
index 463dfc1..df5670b 100644
--- a/src/containers/settings/service-container.tsx
+++ b/src/containers/settings/service-container.tsx
@@ -3,6 +3,9 @@ import { createSelector } from "reselect"
 import { RootState } from "../../scripts/reducer"
 import { ServiceTab } from "../../components/settings/service"
 import { AppDispatch } from "../../scripts/utils"
+import { ServiceConfigs } from "../../schema-types"
+import { saveServiceConfigs, getServiceHooksFromType, removeService, syncWithService } from "../../scripts/models/service"
+import { saveSettings } from "../../scripts/models/app"
 
 const getService = (state: RootState) => state.service
 
@@ -14,7 +17,15 @@ const mapStateToProps = createSelector(
 )
 
 const mapDispatchToProps = (dispatch: AppDispatch) => ({
-    
+    save: (configs: ServiceConfigs) => dispatch(saveServiceConfigs(configs)),
+    remove: () => dispatch(removeService()),
+    blockActions: () => dispatch(saveSettings()),
+    sync: () => dispatch(syncWithService()),
+    authenticate: async (configs: ServiceConfigs) => {
+        const hooks = getServiceHooksFromType(configs.type)
+        if (hooks.authenticate) return await hooks.authenticate(configs)
+        else return true
+    }
 })
 
 const ServiceTabContainer = connect(mapStateToProps, mapDispatchToProps)(ServiceTab)
diff --git a/src/scripts/i18n/en-US.json b/src/scripts/i18n/en-US.json
index 0e61a28..cf10048 100644
--- a/src/scripts/i18n/en-US.json
+++ b/src/scripts/i18n/en-US.json
@@ -179,7 +179,18 @@
     "service": {
         "intro": "Sync across devices with RSS services.",
         "select": "Select a service",
-        "suggest": "Suggest a new service"
+        "suggest": "Suggest a new service",
+        "overwriteWarning": "Local sources will be deleted if they exist in the service.",
+        "groupsWarning": "Groups are only imported on the first sync and will not stay synced.",
+        "endpoint": "Endpoint",
+        "username": "Username",
+        "password": "Password",
+        "unchanged": "Unchanged",
+        "fetchLimit": "Sync limit",
+        "fetchLimitNum": "{count} latest articles",
+        "importGroups": "Import groups",
+        "failure": "Cannot connect to service",
+        "failureHint": "Please check the service configuration or network status."
     },
     "app": {
         "cleanup": "Clean up",
diff --git a/src/scripts/i18n/zh-CN.json b/src/scripts/i18n/zh-CN.json
index 5ad176e..263e268 100644
--- a/src/scripts/i18n/zh-CN.json
+++ b/src/scripts/i18n/zh-CN.json
@@ -177,7 +177,18 @@
     "service": {
         "intro": "通过 RSS 服务跨设备保持同步",
         "select": "选择服务",
-        "suggest": "建议一项新服务"
+        "suggest": "建议一项新服务",
+        "overwriteWarning": "若本地与服务端存在URL相同的订阅源，则本地订阅源将被删除",
+        "groupsWarning": "分组仅在第一次同步时导入而不会与服务端保持同步",
+        "endpoint": "端点",
+        "username": "用户名",
+        "password": "密码",
+        "unchanged": "未更改",
+        "fetchLimit": "同步数量",
+        "fetchLimitNum": "最近 {count} 篇文章",
+        "importGroups": "导入分组",
+        "failure": "无法连接到服务",
+        "failureHint": "请检查服务配置或网络连接"
     },
     "app": {
         "cleanup": "清理",
diff --git a/src/scripts/models/app.ts b/src/scripts/models/app.ts
index 7e4718e..7932042 100644
--- a/src/scripts/models/app.ts
+++ b/src/scripts/models/app.ts
@@ -8,6 +8,7 @@ import { PageActionTypes, SELECT_PAGE, PageType, selectAllArticles, showItemFrom
 import { getCurrentLocale } from "../settings"
 import locales from "../i18n/_locales"
 import * as db from "../db"
+import { SYNC_SERVICE, ServiceActionTypes } from "./service"
 
 export const enum ContextMenuType {
     Hidden, Item, Text, View, Group, Image
@@ -37,6 +38,7 @@ export class AppState {
     locale = null as string
     sourceInit = false
     feedInit = false
+    syncing = false
     fetchingItems = false
     fetchingProgress = 0
     fetchingTotal = 0
@@ -292,6 +294,7 @@ export function appReducer(
     state = new AppState(),
     action: SourceActionTypes | ItemActionTypes | ContextMenuActionTypes | SettingsActionTypes | InitIntlAction
         | MenuActionTypes | LogMenuActionType | FeedActionTypes | PageActionTypes | SourceGroupActionTypes
+        | ServiceActionTypes
 ): AppState {
     switch (action.type) {
         case INIT_INTL: return {
@@ -347,6 +350,17 @@ export function appReducer(
                     feedInit: true
                 }
             }
+        case SYNC_SERVICE:
+            switch (action.status) {
+                case ActionStatus.Request: return {
+                    ...state,
+                    syncing: true
+                }
+                default: return {
+                    ...state,
+                    syncing: false
+                }
+            }
         case FETCH_ITEMS:
             switch (action.status) {
                 case ActionStatus.Request: return {
@@ -452,6 +466,7 @@ export function appReducer(
             ...state,
             settings: {
                 ...state.settings,
+                display: true,
                 saving: !state.settings.saving
             }
         }
diff --git a/src/scripts/models/group.ts b/src/scripts/models/group.ts
index ff50bea..7eaceb7 100644
--- a/src/scripts/models/group.ts
+++ b/src/scripts/models/group.ts
@@ -207,7 +207,7 @@ export function importOPML(): AppThunk {
                 dispatch(fetchItemsRequest(sources.length))
                 let promises = sources.map(([s, gid, url]) => {
                     return dispatch(s).then(sid => {
-                        if (sid !== null) dispatch(addSourceToGroup(gid, sid))
+                        if (sid !== null && gid > -1) dispatch(addSourceToGroup(gid, sid))
                     }).catch(err => {
                         errors.push([url, err])
                     }).finally(() => {
@@ -293,10 +293,12 @@ export function groupReducer(
             })).filter(g => g.isMultiple || g.sids.length == 1)
         ]
         case CREATE_SOURCE_GROUP: return [ ...state, action.group ]
-        case ADD_SOURCE_TO_GROUP: return state.map((g, i) => i == action.groupIndex ? ({
+        case ADD_SOURCE_TO_GROUP: return state.map((g, i) => ({
             ...g,
-            sids: [ ...g.sids, action.sid ]
-        }) : g).filter(g => g.isMultiple || !g.sids.includes(action.sid))
+            sids: i == action.groupIndex 
+                ? [ ...g.sids.filter(sid => sid !== action.sid), action.sid ] 
+                : g.sids.filter(sid => sid !== action.sid)
+        })).filter(g => g.isMultiple || g.sids.length > 0)
         case REMOVE_SOURCE_FROM_GROUP: return [
             ...state.slice(0, action.groupIndex),
             { 
diff --git a/src/scripts/models/item.ts b/src/scripts/models/item.ts
index 6dd1547..c81fb0d 100644
--- a/src/scripts/models/item.ts
+++ b/src/scripts/models/item.ts
@@ -5,7 +5,7 @@ import { RSSSource } from "./source"
 import { FeedActionTypes, INIT_FEED, LOAD_MORE, FilterType, initFeeds } from "./feed"
 import Parser from "@yang991178/rss-parser"
 import { pushNotification, setupAutoFetch } from "./app"
-import { getServiceHooks, syncWithService } from "./service"
+import { getServiceHooks, syncWithService, ServiceActionTypes, SYNC_LOCAL_ITEMS } from "./service"
 
 export class RSSItem {
     _id: string
@@ -22,6 +22,7 @@ export class RSSItem {
     starred?: true
     hidden?: true
     notify?: true
+    serviceRef?: string | number
 
     constructor (item: Parser.Item, source: RSSSource) {
         for (let field of ["title", "link", "creator"]) {
@@ -173,17 +174,14 @@ export function insertItems(items: RSSItem[]): Promise<RSSItem[]> {
 
 export function fetchItems(background = false): AppThunk<Promise<void>> {
     return async (dispatch, getState) => {
-        try {
-            await dispatch(syncWithService())
-        } catch (err) {
-            console.log(err)
-        }
         let promises = new Array<Promise<RSSItem[]>>()
-        if (!getState().app.fetchingItems) {
+        const initState = getState()
+        if (!initState.app.fetchingItems && !initState.app.syncing) {
+            await dispatch(syncWithService())
             let timenow = new Date().getTime()
             let sources = <RSSSource[]>Object.values(getState().sources).filter(s => {
                 let last = s.lastFetched ? s.lastFetched.getTime() : 0
-                return !s.isRemote && ((last > timenow) || (last + (s.fetchFrequency || 0) * 60000 <= timenow))
+                return !s.serviceRef && ((last > timenow) || (last + (s.fetchFrequency || 0) * 60000 <= timenow))
             })
             for (let source of sources) {
                 let promise = RSSSource.fetchItems(source)
@@ -239,12 +237,12 @@ const markUnreadDone = (item: RSSItem): ItemActionTypes => ({
 })
 
 export function markRead(item: RSSItem): AppThunk {
-    return (dispatch, getState) => {
+    return (dispatch) => {
         if (!item.hasRead) {
             db.idb.update({ _id: item._id }, { $set: { hasRead: true } })
             dispatch(markReadDone(item))
-            if (getState().sources[item.source].isRemote) {
-                dispatch(getServiceHooks()).markRead?.(item)
+            if (item.serviceRef) {
+                dispatch(dispatch(getServiceHooks()).markRead?.(item))
             }
         }
     }
@@ -257,6 +255,7 @@ export function markAllRead(sids: number[] = null, date: Date = null, before = t
             let feed = state.feeds[state.page.feedId]
             sids = feed.sids
         }
+        dispatch(dispatch(getServiceHooks()).markAllRead?.(sids, date, before))
         let query = { 
             source: { $in: sids },
             hasRead: false,
@@ -296,17 +295,16 @@ export function markAllRead(sids: number[] = null, date: Date = null, before = t
                 if (date) callback(affectedDocuments as unknown as RSSItem[])
         })
         if (!date) callback()
-        dispatch(getServiceHooks()).markAllRead?.(sids, date, before)
     }
 }
 
 export function markUnread(item: RSSItem): AppThunk {
-    return (dispatch, getState) => {
+    return (dispatch) => {
         if (item.hasRead) {
             db.idb.update({ _id: item._id }, { $set: { hasRead: false } })
             dispatch(markUnreadDone(item))
-            if (getState().sources[item.source].isRemote) {
-                dispatch(getServiceHooks()).markUnread?.(item)
+            if (item.serviceRef) {
+                dispatch(dispatch(getServiceHooks()).markUnread?.(item))
             }
         }
     }
@@ -318,17 +316,17 @@ const toggleStarredDone = (item: RSSItem): ItemActionTypes => ({
 })
 
 export function toggleStarred(item: RSSItem): AppThunk {
-    return (dispatch, getState) => {
+    return (dispatch) => {
         if (item.starred === true) {
             db.idb.update({ _id: item._id }, { $unset: { starred: true } })
         } else {
             db.idb.update({ _id: item._id }, { $set: { starred: true } })
         }
         dispatch(toggleStarredDone(item))
-        if (getState().sources[item.source].isRemote) {
+        if (item.serviceRef) {
             const hooks = dispatch(getServiceHooks())
-            if (item.starred) hooks.unstar?.(item)
-            else hooks.star?.(item)
+            if (item.starred) dispatch(hooks.unstar?.(item))
+            else dispatch(hooks.star?.(item))
         }
     }
 }
@@ -395,7 +393,7 @@ export function applyItemReduction(item: RSSItem, type: string) {
 
 export function itemReducer(
     state: ItemState = {},
-    action: ItemActionTypes | FeedActionTypes
+    action: ItemActionTypes | FeedActionTypes | ServiceActionTypes
 ): ItemState {
     switch (action.type) {
         case FETCH_ITEMS:
@@ -449,6 +447,24 @@ export function itemReducer(
                 default: return state
             }
         }
+        case SYNC_LOCAL_ITEMS: {
+            const unreadSet = new Set(action.unreadIds)
+            const starredSet = new Set(action.starredIds)
+            let nextState = { ...state }
+            for (let [id, item] of Object.entries(state)) {
+                if (item.hasOwnProperty("serviceRef")) {
+                    const nextItem = { ...item }
+                    nextItem.hasRead = !unreadSet.has(nextItem.serviceRef as number)
+                    if (starredSet.has(item.serviceRef as number)) {
+                        nextItem.starred = true
+                    } else {
+                        delete nextItem.starred
+                    }
+                    nextState[id] = nextItem
+                }
+            }
+            return nextState
+        }
         default: return state
     }
 }
\ No newline at end of file
diff --git a/src/scripts/models/service.ts b/src/scripts/models/service.ts
index 8d840e1..e1e83c2 100644
--- a/src/scripts/models/service.ts
+++ b/src/scripts/models/service.ts
@@ -1,13 +1,15 @@
 import { SyncService, ServiceConfigs } from "../../schema-types"
-import { AppThunk } from "../utils"
+import { AppThunk, ActionStatus } from "../utils"
 import { RSSItem } from "./item"
 
 import { feverServiceHooks } from "./services/fever"
+import { saveSettings } from "./app"
+import { deleteSource } from "./source"
 
 export interface ServiceHooks {
     authenticate?: (configs: ServiceConfigs) => Promise<boolean>
     updateSources?: () => AppThunk<Promise<void>>
-    fetchItems?: () => AppThunk<Promise<void>>
+    fetchItems?: (background: boolean) => AppThunk<Promise<void>>
     syncItems?: () => AppThunk<Promise<void>>
     markRead?: (item: RSSItem) => AppThunk
     markUnread?: (item: RSSItem) => AppThunk
@@ -29,25 +31,71 @@ export function getServiceHooks(): AppThunk<ServiceHooks> {
     }
 }
 
-export function syncWithService(): AppThunk<Promise<void>> {
-    return async (dispatch) => {
+export function syncWithService(background = false): AppThunk<Promise<void>> {
+    return async (dispatch, getState) => {
         const hooks = dispatch(getServiceHooks())
         if (hooks.updateSources && hooks.fetchItems && hooks.syncItems) {
-            await dispatch(hooks.updateSources())
-            await dispatch(hooks.fetchItems())
-            await dispatch(hooks.syncItems())
+            try {
+                dispatch({
+                    type: SYNC_SERVICE,
+                    status: ActionStatus.Request
+                })
+                await dispatch(hooks.updateSources())
+                await dispatch(hooks.syncItems())
+                await dispatch(hooks.fetchItems(background))
+                dispatch({
+                    type: SYNC_SERVICE,
+                    status: ActionStatus.Success
+                })
+            } catch (err) {
+                console.log(err)
+                dispatch({
+                    type: SYNC_SERVICE,
+                    status: ActionStatus.Failure,
+                    err: err
+                })
+            } finally {
+                if (getState().app.settings.saving) dispatch(saveSettings())
+            }
         }
     }
 }
 
+export function removeService(): AppThunk<Promise<void>> {
+    return async (dispatch, getState) => {
+        dispatch(saveSettings())
+        const state = getState()
+        const promises = Object.values(state.sources).filter(s => s.serviceRef).map(async s => {
+            await dispatch(deleteSource(s, true))
+        })
+        await Promise.all(promises)
+        dispatch(saveServiceConfigs({ type: SyncService.None }))
+        dispatch(saveSettings())
+    }
+}
+
 export const SAVE_SERVICE_CONFIGS = "SAVE_SERVICE_CONFIGS"
+export const SYNC_SERVICE = "SYNC_SERVICE"
+export const SYNC_LOCAL_ITEMS = "SYNC_LOCAL_ITEMS"
 
 interface SaveServiceConfigsAction {
     type: typeof SAVE_SERVICE_CONFIGS
     configs: ServiceConfigs
 }
 
-export type ServiceActionTypes = SaveServiceConfigsAction
+interface SyncWithServiceAction {
+    type: typeof SYNC_SERVICE
+    status: ActionStatus
+    err?
+}
+
+interface SyncLocalItemsAction {
+    type: typeof SYNC_LOCAL_ITEMS
+    unreadIds: number[]
+    starredIds: number[]
+}
+
+export type ServiceActionTypes = SaveServiceConfigsAction | SyncWithServiceAction | SyncLocalItemsAction
 
 export function saveServiceConfigs(configs: ServiceConfigs): AppThunk {
     return (dispatch) => {
@@ -59,6 +107,14 @@ export function saveServiceConfigs(configs: ServiceConfigs): AppThunk {
     }
 }
 
+export function syncLocalItems(unread: number[], starred: number[]): ServiceActionTypes {
+    return {
+        type: SYNC_LOCAL_ITEMS,
+        unreadIds: unread,
+        starredIds: starred
+    }
+}
+
 export function serviceReducer(
     state = window.settings.getServiceConfigs(),
     action: ServiceActionTypes
diff --git a/src/scripts/models/services/fever.ts b/src/scripts/models/services/fever.ts
index 0d8305b..62432ab 100644
--- a/src/scripts/models/services/fever.ts
+++ b/src/scripts/models/services/fever.ts
@@ -1,23 +1,46 @@
-import { ServiceHooks } from "../service"
-import { ServiceConfigs } from "../../../schema-types"
+import intl from "react-intl-universal"
+import * as db from "../../db"
+import { ServiceHooks, saveServiceConfigs, syncLocalItems } from "../service"
+import { ServiceConfigs, SyncService } from "../../../schema-types"
+import { createSourceGroup, addSourceToGroup } from "../group"
+import { RSSSource, insertSource, addSourceSuccess, updateSource, deleteSource, updateUnreadCounts } from "../source"
+import { fetchFavicon, htmlDecode, domParser } from "../../utils"
+import { saveSettings, pushNotification } from "../app"
+import { initFeeds, FilterType } from "../feed"
+import { RSSItem, insertItems, fetchItemsSuccess } from "../item"
+import { SourceRule } from "../rule"
 
 export interface FeverConfigs extends ServiceConfigs {
+    type: SyncService.Fever
     endpoint: string
     username: string
-    password: string
     apiKey: string
+    fetchLimit: number
     lastId?: number
+    importGroups?: boolean
 }
 
-async function fetchAPI(configs: FeverConfigs, params="") {
-    const response = await fetch(configs.endpoint + params, {
+async function fetchAPI(configs: FeverConfigs, params="", postparams="") {
+    const response = await fetch(configs.endpoint + "?api" + params, {
         method: "POST",
         headers: { "content-type": "application/x-www-form-urlencoded" },
-        body: `api_key=${configs.apiKey}`
+        body: `api_key=${configs.apiKey}${postparams}`
     })
     return await response.json()
 }
 
+async function markItem(configs: FeverConfigs, item: RSSItem, as: string) {
+    if (item.serviceRef) {
+        try {
+            await fetchAPI(configs, "", `&mark=item&as=${as}&id=${item.serviceRef}`)
+        } catch (err) {
+            console.log(err)
+        }
+    }
+}
+
+const APIError = () => new Error(intl.get("service.failure")) 
+
 export const feverServiceHooks: ServiceHooks = {
     authenticate: async (configs: FeverConfigs) => {
         try {
@@ -25,5 +48,252 @@ export const feverServiceHooks: ServiceHooks = {
         } catch {
             return false
         }
-    }
+    },
+
+    updateSources: () => async (dispatch, getState) => {
+        const initState = getState()
+        const configs = initState.service as FeverConfigs
+        const response = await fetchAPI(configs, "&feeds")
+        const feeds: any[] = response.feeds
+        const feedGroups: any[] = response.feeds_groups
+        if (feeds === undefined) throw APIError()
+        let groupsMap: Map<number, string>
+        if (configs.importGroups) {
+            // Import groups on the first sync
+            const groups: any[] = (await fetchAPI(configs, "&groups")).groups
+            if (groups === undefined || feedGroups === undefined) throw APIError()
+            groupsMap = new Map()
+            for (let group of groups) {
+                dispatch(createSourceGroup(group.title))
+                groupsMap.set(group.id, group.title)
+            }
+        }
+        const existing = new Map<number, RSSSource>()
+        for (let source of Object.values(initState.sources)) {
+            if (source.serviceRef) {
+                existing.set(source.serviceRef as number, source)
+            }
+        }
+        const forceSettings = () => {
+            if (!(getState().app.settings.saving)) dispatch(saveSettings())
+        }
+        let promises = feeds.map(f => new Promise<RSSSource>((resolve, reject) => {
+            if (existing.has(f.id)) {
+                const doc = existing.get(f.id)
+                existing.delete(f.id)
+                resolve(doc)
+            } else {
+                db.sdb.findOne({ url: f.url }, (err, doc) => {
+                    if (err) {
+                        reject(err)
+                    } else if (doc === null) {
+                        // Create a new source
+                        forceSettings()
+                        let source = new RSSSource(f.url, f.title)
+                        source.serviceRef = f.id
+                        const domain = source.url.split("/").slice(0, 3).join("/")
+                        fetchFavicon(domain).then(favicon => {
+                            if (favicon) source.iconurl = favicon
+                            dispatch(insertSource(source))
+                                .then((inserted) => {
+                                    inserted.unreadCount = 0
+                                    resolve(inserted)
+                                    dispatch(addSourceSuccess(inserted, true))
+                                })
+                                .catch((err) => {
+                                    reject(err)
+                                })
+                        })
+                    } else if (doc.serviceRef !== f.id) {
+                        // Mark an existing source as remote and remove all items
+                        forceSettings()
+                        doc.serviceRef = f.id
+                        doc.unreadCount = 0
+                        dispatch(updateSource(doc)).finally(() => {
+                            db.idb.remove({ source: doc.sid }, { multi: true }, (err) => {
+                                if (err) reject(err)
+                                else resolve(doc)
+                            })
+                        })
+                    } else {
+                        resolve(doc)
+                    }
+                })
+            }
+        }))
+        for (let [_, source] of existing) {
+            // Delete sources removed from the service side
+            forceSettings()
+            promises.push(dispatch(deleteSource(source, true)).then(() => null))
+        }
+        let sources = (await Promise.all(promises)).filter(s => s)
+        if (groupsMap) {
+            // Add sources to imported groups
+            forceSettings()
+            let sourcesMap = new Map<number, number>()
+            for (let source of sources) sourcesMap.set(source.serviceRef as number, source.sid)
+            for (let group of feedGroups) {
+                for (let fid of group.feed_ids.split(",").map(s => parseInt(s))) {
+                    if (sourcesMap.has(fid)) {
+                        const gid = dispatch(createSourceGroup(groupsMap.get(group.group_id)))
+                        dispatch(addSourceToGroup(gid, sourcesMap.get(fid)))
+                    }
+                }
+            }
+            delete configs.importGroups
+            dispatch(saveServiceConfigs(configs))
+        }
+    },
+
+    fetchItems: (background) => async (dispatch, getState) => {
+        const state = getState()
+        const configs = state.service as FeverConfigs
+        const items = new Array()
+        configs.lastId = configs.lastId || 0
+        let min = 2147483647
+        let response
+        do {
+            response = await fetchAPI(configs, `&items&max_id=${min}`)
+            if (response.items === undefined) throw APIError()
+            items.push(...response.items.filter(i => i.id > configs.lastId))
+            min = response.items.reduce((m, n) => Math.min(m, n.id), min)
+        } while (min > configs.lastId && response.items.length >= 50 && items.length < configs.fetchLimit)
+        configs.lastId = items.reduce((m, n) => Math.max(m, n.id), configs.lastId)
+        if (items.length > 0) {
+            const fidMap = new Map<number, RSSSource>()
+            for (let source of Object.values(state.sources)) {
+                if (source.serviceRef) {
+                    fidMap.set(source.serviceRef as number, source)
+                }
+            }
+            const parsedItems = items.map(i => {
+                const source = fidMap.get(i.feed_id)
+                const item = {
+                    source: source.sid,
+                    title: i.title,
+                    link: i.url,
+                    date: new Date(i.created_on_time * 1000),
+                    fetchedDate: new Date(),
+                    content: i.html,
+                    snippet: htmlDecode(i.html).trim(),
+                    creator: i.author,
+                    hasRead: Boolean(i.is_read),
+                    serviceRef: i.id
+                } as RSSItem
+                if (i.is_saved) item.starred = true
+                // Try to get the thumbnail of the item
+                let dom = domParser.parseFromString(item.content, "text/html")
+                let baseEl = dom.createElement('base')
+                baseEl.setAttribute('href', item.link.split("/").slice(0, 3).join("/"))
+                dom.head.append(baseEl)
+                let img = dom.querySelector("img")
+                if (img && img.src) { 
+                    item.thumb = img.src
+                } else {
+                    let a = dom.querySelector("body>ul>li:first-child>a") as HTMLAnchorElement
+                    if (a && /, image\/generic$/.test(a.innerText) && a.href)
+                        item.thumb = a.href
+                }
+                // Apply rules and sync back to the service
+                if (source.rules) SourceRule.applyAll(source.rules, item)
+                if (Boolean(i.is_read) !== item.hasRead) 
+                    markItem(configs, item, item.hasRead ? "read" : "unread")
+                if (Boolean(i.is_saved) !== Boolean(item.starred)) 
+                    markItem(configs, item, item.starred ? "saved" : "unsaved")
+                return item
+            })
+            const inserted = await insertItems(parsedItems)
+            dispatch(fetchItemsSuccess(inserted.reverse(), getState().items))
+            if (background) {
+                for (let item of inserted) {
+                    if (item.notify) dispatch(pushNotification(item))
+                }
+                if (inserted.length > 0) window.utils.requestAttention()
+            }
+            dispatch(saveServiceConfigs(configs))
+        }
+    },
+
+    syncItems: () => async (dispatch, getState) => {
+        const state = getState()
+        const configs = state.service as FeverConfigs
+        const unreadResponse = await fetchAPI(configs, "&unread_item_ids")
+        const starredResponse = await fetchAPI(configs, "&saved_item_ids")
+        if (typeof unreadResponse.unread_item_ids !== "string" || typeof starredResponse.saved_item_ids !== "string") {
+            throw APIError()
+        }
+        const unreadFids: number[] = unreadResponse.unread_item_ids.split(",").map(s => parseInt(s))
+        const starredFids: number[] = starredResponse.saved_item_ids.split(",").map(s => parseInt(s))
+        const promises = new Array<Promise<number>>()
+        promises.push(new Promise((resolve) => {
+            db.idb.update({ 
+                serviceRef: { $exists: true, $in: unreadFids }, 
+                hasRead: true 
+            }, { $set: { hasRead: false } }, { multi: true }, (_, num) => resolve(num))
+        }))
+        promises.push(new Promise((resolve) => {
+            db.idb.update({ 
+                serviceRef: { $exists: true, $nin: unreadFids }, 
+                hasRead: false 
+            }, { $set: { hasRead: true } }, { multi: true }, (_, num) => resolve(num))
+        }))
+        promises.push(new Promise((resolve) => {
+            db.idb.update({ 
+                serviceRef: { $exists: true, $in: starredFids }, 
+                starred: { $exists: false } 
+            }, { $set: { starred: true } }, { multi: true }, (_, num) => resolve(num))
+        }))
+        promises.push(new Promise((resolve) => {
+            db.idb.update({ 
+                serviceRef: { $exists: true, $nin: starredFids }, 
+                starred: true 
+            }, { $unset: { starred: true } }, { multi: true }, (_, num) => resolve(num))
+        }))
+        const affected = (await Promise.all(promises)).reduce((a, b) => a + b, 0)
+        if (affected > 0) {
+            dispatch(syncLocalItems(unreadFids, starredFids))
+            if (!(state.page.filter.type & FilterType.ShowRead) || !(state.page.filter.type & FilterType.ShowNotStarred)) {
+                dispatch(initFeeds(true))
+            }
+            await dispatch(updateUnreadCounts())
+        }
+    },
+
+    markAllRead: (sids, date, before) => async (_, getState) => {
+        const state = getState()
+        const configs = state.service as FeverConfigs
+        if (date && !before) {
+            const iids = state.feeds[state.page.feedId].iids
+            const items = iids.map(iid => state.items[iid]).filter(i => i.date.getTime() >= date.getTime())
+            for (let item of items) {
+                if (item.serviceRef) {
+                    markItem(configs, item, "read")
+                }
+            }
+        } else {
+            const sources = sids.map(sid => state.sources[sid])
+            const timestamp = Math.floor((date ? date.getTime() : Date.now()) / 1000) + 1
+            for (let source of sources) {
+                if (source.serviceRef) {
+                    fetchAPI(configs, "", `&mark=feed&as=read&id=${source.serviceRef}&before=${timestamp}`)
+                }
+            }
+        }
+    },
+
+    markRead: (item: RSSItem) => async (_, getState) => {
+        await markItem(getState().service as FeverConfigs, item, "read")
+    },
+
+    markUnread: (item: RSSItem) => async (_, getState) => {
+        await markItem(getState().service as FeverConfigs, item, "unread")
+    },
+
+    star: (item: RSSItem) => async (_, getState) => {
+        await markItem(getState().service as FeverConfigs, item, "saved")
+    },
+
+    unstar: (item: RSSItem) => async (_, getState) => {
+        await markItem(getState().service as FeverConfigs, item, "unsaved")
+    },
 }
\ No newline at end of file
diff --git a/src/scripts/models/source.ts b/src/scripts/models/source.ts
index e9c8dca..ecf8603 100644
--- a/src/scripts/models/source.ts
+++ b/src/scripts/models/source.ts
@@ -13,12 +13,12 @@ export enum SourceOpenTarget {
 export class RSSSource {
     sid: number
     url: string
-    iconurl: string
+    iconurl?: string
     name: string
     openTarget: SourceOpenTarget
     unreadCount: number
     lastFetched: Date
-    isRemote?: true
+    serviceRef?: string | number
     fetchFrequency?: number // in minutes
     rules?: SourceRule[]
 
@@ -157,6 +157,14 @@ function unreadCount(source: RSSSource): Promise<RSSSource> {
     })
 }
 
+export function updateUnreadCounts(): AppThunk<Promise<void>> {
+    return async (dispatch, getState) => {
+        await Promise.all(Object.values(getState().sources).map(async s => {
+            dispatch(updateSourceDone(await unreadCount(s)))
+        }))
+    }
+}
+
 export function initSources(): AppThunk<Promise<void>> {
     return (dispatch) => {
         dispatch(initSourcesRequest())
@@ -206,7 +214,7 @@ export function addSourceFailure(err, batch: boolean): SourceActionTypes {
 }
 
 let insertPromises = Promise.resolve()
-function insertSource(source: RSSSource): AppThunk<Promise<RSSSource>> {
+export function insertSource(source: RSSSource): AppThunk<Promise<RSSSource>> {
     return (_, getState) => {
         return new Promise((resolve, reject) => {
             insertPromises = insertPromises.then(() => new Promise(innerResolve => {
@@ -268,8 +276,8 @@ export function updateSourceDone(source: RSSSource): SourceActionTypes {
     }
 }
 
-export function updateSource(source: RSSSource): AppThunk {
-    return (dispatch) => {
+export function updateSource(source: RSSSource): AppThunk<Promise<void>> {
+    return (dispatch) => new Promise((resolve) => {
         let sourceCopy = { ...source }
         delete sourceCopy.sid
         delete sourceCopy.unreadCount
@@ -277,8 +285,9 @@ export function updateSource(source: RSSSource): AppThunk {
             if (!err) {
                 dispatch(updateSourceDone(source))
             }
+            resolve()
         })
-    }
+    })
 }
 
 export function deleteSourceDone(source: RSSSource): SourceActionTypes {