diff --git a/app/src/main/java/org/koitharu/kotatsu/core/prefs/AppSettings.kt b/app/src/main/java/org/koitharu/kotatsu/core/prefs/AppSettings.kt
index b81fcbe7a..6b24b25e1 100644
--- a/app/src/main/java/org/koitharu/kotatsu/core/prefs/AppSettings.kt
+++ b/app/src/main/java/org/koitharu/kotatsu/core/prefs/AppSettings.kt
@@ -312,6 +312,7 @@ class AppSettings(context: Context) {
 		const val KEY_DOWNLOADS_SLOWDOWN = "downloads_slowdown"
 		const val KEY_ALL_FAVOURITES_VISIBLE = "all_favourites_visible"
 		const val KEY_DOH = "doh"
+		const val KEY_SYNC = "sync"
 
 		// About
 		const val KEY_APP_UPDATE = "app_update"
diff --git a/app/src/main/java/org/koitharu/kotatsu/settings/ContentSettingsFragment.kt b/app/src/main/java/org/koitharu/kotatsu/settings/ContentSettingsFragment.kt
index 800599441..d9de212d6 100644
--- a/app/src/main/java/org/koitharu/kotatsu/settings/ContentSettingsFragment.kt
+++ b/app/src/main/java/org/koitharu/kotatsu/settings/ContentSettingsFragment.kt
@@ -1,7 +1,9 @@
 package org.koitharu.kotatsu.settings
 
+import android.content.Intent
 import android.content.SharedPreferences
 import android.os.Bundle
+import android.provider.Settings
 import android.view.View
 import androidx.preference.ListPreference
 import androidx.preference.Preference
@@ -76,6 +78,10 @@ class ContentSettingsFragment :
 			AppSettings.KEY_SOURCES_HIDDEN -> {
 				bindRemoteSourcesSummary()
 			}
+			AppSettings.KEY_SYNC -> {
+				val intent = Intent(Settings.ACTION_SYNC_SETTINGS)
+				startActivity(intent)
+			}
 		}
 	}
 
diff --git a/app/src/main/java/org/koitharu/kotatsu/sync/domain/SyncHelper.kt b/app/src/main/java/org/koitharu/kotatsu/sync/domain/SyncHelper.kt
index 35b3c7408..f5dbfb9d5 100644
--- a/app/src/main/java/org/koitharu/kotatsu/sync/domain/SyncHelper.kt
+++ b/app/src/main/java/org/koitharu/kotatsu/sync/domain/SyncHelper.kt
@@ -5,6 +5,7 @@ import android.content.*
 import android.database.Cursor
 import android.net.Uri
 import androidx.annotation.WorkerThread
+import androidx.core.content.contentValuesOf
 import okhttp3.OkHttpClient
 import okhttp3.Request
 import org.json.JSONArray
@@ -13,9 +14,9 @@ import org.koitharu.kotatsu.R
 import org.koitharu.kotatsu.core.db.*
 import org.koitharu.kotatsu.parsers.util.json.mapJSONTo
 import org.koitharu.kotatsu.parsers.util.parseJson
+import org.koitharu.kotatsu.sync.data.SyncAuthApi
 import org.koitharu.kotatsu.sync.data.SyncAuthenticator
 import org.koitharu.kotatsu.sync.data.SyncInterceptor
-import org.koitharu.kotatsu.sync.data.SyncAuthApi
 import org.koitharu.kotatsu.utils.GZipInterceptor
 import org.koitharu.kotatsu.utils.ext.toContentValues
 import org.koitharu.kotatsu.utils.ext.toJson
@@ -86,6 +87,7 @@ class SyncHelper(
 			.withSelection("updated_at < ?", arrayOf(timestamp.toString()))
 			.build()
 		json.mapJSONTo(operations) { jo ->
+			operations.addAll(upsertManga(jo.removeJSONObject("manga"), AUTHORITY_HISTORY))
 			ContentProviderOperation.newInsert(uri)
 				.withValues(jo.toContentValues())
 				.build()
@@ -114,6 +116,7 @@ class SyncHelper(
 			.withSelection("created_at < ?", arrayOf(timestamp.toString()))
 			.build()
 		json.mapJSONTo(operations) { jo ->
+			operations.addAll(upsertManga(jo.removeJSONObject("manga"), AUTHORITY_FAVOURITES))
 			ContentProviderOperation.newInsert(uri)
 				.withValues(jo.toContentValues())
 				.build()
@@ -121,6 +124,31 @@ class SyncHelper(
 		return provider.applyBatch(operations)
 	}
 
+	private fun upsertManga(json: JSONObject, authority: String): List<ContentProviderOperation> {
+		val tags = json.removeJSONArray(TABLE_TAGS)
+		val result = ArrayList<ContentProviderOperation>(tags.length() * 2 + 1)
+		for (i in 0 until tags.length()) {
+			val tag = tags.getJSONObject(i)
+			result += ContentProviderOperation.newInsert(uri(authority, TABLE_TAGS))
+				.withValues(tag.toContentValues())
+				.build()
+			result += ContentProviderOperation.newInsert(uri(authority, TABLE_MANGA_TAGS))
+				.withValues(
+					contentValuesOf(
+						"manga_id" to json.getLong("manga_id"),
+						"tag_id" to tag.getLong("tag_id"),
+					)
+				).build()
+		}
+		result.add(
+			0,
+			ContentProviderOperation.newInsert(uri(authority, TABLE_MANGA))
+				.withValues(json.toContentValues())
+				.build()
+		)
+		return result
+	}
+
 	private fun getHistory(): JSONArray {
 		return provider.query(AUTHORITY_HISTORY, TABLE_HISTORY).use { cursor ->
 			val json = JSONArray()
@@ -217,4 +245,8 @@ class SyncHelper(
 	}
 
 	private fun uri(authority: String, table: String) = Uri.parse("content://$authority/$table")
+
+	private fun JSONObject.removeJSONObject(name: String) = remove(name) as JSONObject
+
+	private fun JSONObject.removeJSONArray(name: String) = remove(name) as JSONArray
 }
\ No newline at end of file
diff --git a/app/src/main/java/org/koitharu/kotatsu/sync/ui/SyncProvider.kt b/app/src/main/java/org/koitharu/kotatsu/sync/ui/SyncProvider.kt
index 02f296aac..604e6de9d 100644
--- a/app/src/main/java/org/koitharu/kotatsu/sync/ui/SyncProvider.kt
+++ b/app/src/main/java/org/koitharu/kotatsu/sync/ui/SyncProvider.kt
@@ -7,10 +7,11 @@ import android.content.ContentValues
 import android.database.Cursor
 import android.database.sqlite.SQLiteDatabase
 import android.net.Uri
+import androidx.sqlite.db.SupportSQLiteDatabase
 import androidx.sqlite.db.SupportSQLiteQueryBuilder
+import java.util.concurrent.Callable
 import org.koin.android.ext.android.inject
 import org.koitharu.kotatsu.core.db.*
-import java.util.concurrent.Callable
 
 abstract class SyncProvider : ContentProvider() {
 
@@ -55,15 +56,14 @@ abstract class SyncProvider : ContentProvider() {
 			return null
 		}
 		val db = database.openHelper.writableDatabase
-		db.insert(table, SQLiteDatabase.CONFLICT_REPLACE, values)
-		return null
+		if (db.insert(table, SQLiteDatabase.CONFLICT_IGNORE, values) < 0) {
+			db.update(table, values)
+		}
+		return uri
 	}
 
 	override fun delete(uri: Uri, selection: String?, selectionArgs: Array<out String>?): Int {
-		val table = getTableName(uri)
-		if (table == null) {
-			return 0
-		}
+		val table = getTableName(uri) ?: return 0
 		return database.openHelper.writableDatabase.delete(table, selection, selectionArgs)
 	}
 
@@ -77,14 +77,35 @@ abstract class SyncProvider : ContentProvider() {
 	}
 
 	override fun applyBatch(operations: ArrayList<ContentProviderOperation>): Array<ContentProviderResult> {
-		return database.runInTransaction(Callable { super.applyBatch(operations) })
+		return runAtomicTransaction { super.applyBatch(operations) }
 	}
 
 	override fun bulkInsert(uri: Uri, values: Array<out ContentValues>): Int {
-		return database.runInTransaction(Callable { super.bulkInsert(uri, values) })
+		return runAtomicTransaction { super.bulkInsert(uri, values) }
 	}
 
 	private fun getTableName(uri: Uri): String? {
 		return uri.pathSegments.singleOrNull()?.takeIf { it in supportedTables }
 	}
+
+	private fun <R> runAtomicTransaction(callable: Callable<R>): R {
+		return synchronized(database) {
+			database.runInTransaction(callable)
+		}
+	}
+
+	private fun SupportSQLiteDatabase.update(table: String, values: ContentValues) {
+		val keys = when (table) {
+			TABLE_TAGS -> listOf("tag_id")
+			TABLE_MANGA_TAGS -> listOf("tag_id", "manga_id")
+			TABLE_MANGA -> listOf("manga_id")
+			TABLE_FAVOURITES -> listOf("manga_id", "category_id")
+			TABLE_FAVOURITE_CATEGORIES -> listOf("category_id")
+			TABLE_HISTORY -> listOf("manga_id")
+			else -> throw IllegalArgumentException("Update for $table is not supported")
+		}
+		val whereClause = keys.joinToString(" AND ") { "`$it` = ?" }
+		val whereArgs = Array<Any>(keys.size) { i -> values.get("`${keys[i]}`") ?: values.get(keys[i]) }
+		this.update(table, SQLiteDatabase.CONFLICT_IGNORE, values, whereClause, whereArgs)
+	}
 }
\ No newline at end of file
diff --git a/app/src/main/java/org/koitharu/kotatsu/utils/ext/CursorExt.kt b/app/src/main/java/org/koitharu/kotatsu/utils/ext/CursorExt.kt
index 852d92e10..eeab153b0 100644
--- a/app/src/main/java/org/koitharu/kotatsu/utils/ext/CursorExt.kt
+++ b/app/src/main/java/org/koitharu/kotatsu/utils/ext/CursorExt.kt
@@ -24,7 +24,7 @@ fun JSONObject.toContentValues(): ContentValues {
 	for (key in keys()) {
 		val name = key.escapeName()
 		when (val value = get(key)) {
-			null -> cv.putNull(name)
+			JSONObject.NULL, "null", null -> cv.putNull(name)
 			is String -> cv.put(name, value)
 			is Float -> cv.put(name, value)
 			is Double -> cv.put(name, value)
diff --git a/app/src/main/res/values/constants.xml b/app/src/main/res/values/constants.xml
index e63a0cb2d..12c41ccbf 100644
--- a/app/src/main/res/values/constants.xml
+++ b/app/src/main/res/values/constants.xml
@@ -5,7 +5,7 @@
 	<string name="url_forpda" translatable="false">https://4pda.to/forum/index.php?showtopic=697669</string>
 	<string name="url_weblate" translatable="false">https://hosted.weblate.org/engage/kotatsu</string>
 	<string name="account_type_sync" translatable="false">org.kotatsu.sync</string>
-	<string name="url_sync_server" translatable="false">http://192.168.0.113:8080</string>
+	<string name="url_sync_server" translatable="false">http://95.216.215.49:8080</string>
 	<string-array name="values_theme" translatable="false">
 		<item>-1</item>
 		<item>1</item>
diff --git a/app/src/main/res/xml/pref_content.xml b/app/src/main/res/xml/pref_content.xml
index 7b48494ea..c7f6ef630 100644
--- a/app/src/main/res/xml/pref_content.xml
+++ b/app/src/main/res/xml/pref_content.xml
@@ -40,9 +40,14 @@
 		android:valueTo="5"
 		app:defaultValue="2" />
 
+	<Preference
+		android:key="sync"
+		android:persistent="false"
+		android:summary="@string/sync_title"
+		android:title="@string/sync" />
+
 	<PreferenceScreen
 		android:fragment="org.koitharu.kotatsu.settings.backup.BackupSettingsFragment"
-		android:title="@string/backup_restore"
-		app:allowDividerAbove="true" />
+		android:title="@string/backup_restore" />
 
 </PreferenceScreen>
\ No newline at end of file