diff --git a/Pixiview.Android/Properties/AndroidManifest.xml b/Pixiview.Android/Properties/AndroidManifest.xml
index 2390d4e..ab7e634 100644
--- a/Pixiview.Android/Properties/AndroidManifest.xml
+++ b/Pixiview.Android/Properties/AndroidManifest.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionName="1.0.524" package="org.tsanie.pixiview" android:versionCode="15">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionName="1.0.524" package="org.tsanie.pixiview" android:versionCode="16">
 	<uses-sdk android:minSdkVersion="25" android:targetSdkVersion="28" />
 	<application android:label="Pixiview" android:icon="@mipmap/icon" android:roundIcon="@mipmap/icon_round"></application>
 	<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
diff --git a/Pixiview.iOS.OpenExtension/Info.plist b/Pixiview.iOS.OpenExtension/Info.plist
index ffb57f4..2107d99 100644
--- a/Pixiview.iOS.OpenExtension/Info.plist
+++ b/Pixiview.iOS.OpenExtension/Info.plist
@@ -31,6 +31,6 @@
 	<key>CFBundleShortVersionString</key>
 	<string>1.0.524</string>
 	<key>CFBundleVersion</key>
-	<string>15</string>
+	<string>16</string>
 </dict>
 </plist>
diff --git a/Pixiview.iOS/Info.plist b/Pixiview.iOS/Info.plist
index d9a0ab7..98e6103 100644
--- a/Pixiview.iOS/Info.plist
+++ b/Pixiview.iOS/Info.plist
@@ -81,7 +81,7 @@
 	<key>CFBundleShortVersionString</key>
 	<string>1.0.524</string>
 	<key>CFBundleVersion</key>
-	<string>15</string>
+	<string>16</string>
 	<key>CFBundleDevelopmentRegion</key>
 	<string>China</string>
 </dict>
diff --git a/Pixiview/Illust/FavoritesPage.xaml.cs b/Pixiview/Illust/FavoritesPage.xaml.cs
index f4329b0..4e50fd6 100644
--- a/Pixiview/Illust/FavoritesPage.xaml.cs
+++ b/Pixiview/Illust/FavoritesPage.xaml.cs
@@ -87,8 +87,9 @@ namespace Pixiview.Illust
             base.OnUnload();
         }
 
-        protected override IEnumerable<IllustItem> DoGetIllustList(IllustItem[] data)
+        protected override IEnumerable<IllustItem> DoGetIllustList(IllustItem[] data, out int tag)
         {
+            tag = startIndex;
             return data;
         }
 
@@ -431,7 +432,8 @@ namespace Pixiview.Illust
                     }
                 }
                 return true;
-            }, () =>
+            },
+            complete: () =>
             {
                 Stores.SaveFavoritesIllusts();
 
diff --git a/Pixiview/Illust/IllustCollectionPage.cs b/Pixiview/Illust/IllustCollectionPage.cs
index a4ff6b4..a0351fc 100644
--- a/Pixiview/Illust/IllustCollectionPage.cs
+++ b/Pixiview/Illust/IllustCollectionPage.cs
@@ -77,13 +77,16 @@ namespace Pixiview.Illust
         protected double topOffset;
         protected string lastError;
 
+        private readonly object sync = new object();
+        private readonly Queue<ParallelTask> tasks;
         private T illustData;
-        private ParallelTask task;
 
         public IllustCollectionPage()
         {
             commandIllustImageTapped = new Command<IllustItem>(OnIllustImageTapped);
             commandUserTapped = new Command<IIllustItem>(OnIllustUserItemTapped);
+            tasks = new Queue<ParallelTask>();
+
             BindingContext = this;
         }
 
@@ -117,10 +120,15 @@ namespace Pixiview.Illust
 
         public override void OnUnload()
         {
-            if (task != null)
+            lock (sync)
             {
-                task.Dispose();
-                task = null;
+                while (tasks.TryDequeue(out var task))
+                {
+                    if (task != null)
+                    {
+                        task.Dispose();
+                    }
+                }
             }
             InvalidateCollection();
             Illusts = null;
@@ -195,7 +203,7 @@ namespace Pixiview.Illust
         #endregion
 
         protected abstract T DoLoadIllustData(bool force);
-        protected abstract IEnumerable<IllustItem> DoGetIllustList(T data);
+        protected abstract IEnumerable<IllustItem> DoGetIllustList(T data, out int tag);
 
         protected virtual IllustCollection GetIllustsLoadedCollection(IllustCollection collection, bool bottom)
         {
@@ -614,7 +622,7 @@ namespace Pixiview.Illust
             }
 
             var r18 = Configs.IsOnR18;
-            var data = DoGetIllustList(illustData).Where(i => i != null && (r18 || !i.IsRestrict));
+            var data = DoGetIllustList(illustData, out int tag).Where(i => i != null && (r18 || !i.IsRestrict));
 
             var collection = new IllustCollection(data);
             var favorites = Stores.Favorites;
@@ -655,19 +663,31 @@ namespace Pixiview.Illust
             }
             DoIllustsLoaded(collection, bottom);
 
-            DoLoadImages(collection);
+            DoLoadImages(collection, tag);
         }
 
-        void DoLoadImages(IllustCollection collection)
+        private void DoLoadImages(IllustCollection collection, int tag)
         {
-            if (task != null)
+            lock (sync)
             {
-                task.Dispose();
-                task = null;
+                if (tasks.TryPeek(out var peek))
+                {
+                    if (peek.TagIndex >= tag)
+                    {
+                        App.DebugPrint($"tasks expired ({tasks.Count}), peek: {peek.TagIndex}, now: {tag}, will be disposing.");
+                        while (tasks.TryPeek(out var t))
+                        {
+                            if (t != null)
+                            {
+                                t.Dispose();
+                            }
+                        }
+                    }
+                }
             }
             var list = collection.Where(i => i.Image == null || i.ProfileImage == null).ToArray();
 
-            task = ParallelTask.Start("collection.load", 0, list.Length, Configs.MaxThreads, i =>
+            var task = ParallelTask.Start("collection.load", 0, list.Length, Configs.MaxThreads, i =>
             {
                 if (!collection.Running)
                 {
@@ -695,7 +715,12 @@ namespace Pixiview.Illust
                     }
                 }
                 return true;
-            });
+            }, tagIndex: tag);
+
+            lock (sync)
+            {
+                tasks.Enqueue(task);
+            }
         }
 
         #endregion
diff --git a/Pixiview/Illust/MainPage.xaml.cs b/Pixiview/Illust/MainPage.xaml.cs
index 32d1098..9440cac 100644
--- a/Pixiview/Illust/MainPage.xaml.cs
+++ b/Pixiview/Illust/MainPage.xaml.cs
@@ -57,8 +57,9 @@ namespace Pixiview.Illust
         }
 #endif
 
-        protected override IEnumerable<IllustItem> DoGetIllustList(IllustData data)
+        protected override IEnumerable<IllustItem> DoGetIllustList(IllustData data, out int tag)
         {
+            tag = 0;
             if (data.body == null)
             {
                 return null;
diff --git a/Pixiview/Illust/RankingPage.xaml.cs b/Pixiview/Illust/RankingPage.xaml.cs
index 19b428e..eb78819 100644
--- a/Pixiview/Illust/RankingPage.xaml.cs
+++ b/Pixiview/Illust/RankingPage.xaml.cs
@@ -162,8 +162,9 @@ namespace Pixiview.Illust
             }
         }
 
-        protected override IEnumerable<IllustItem> DoGetIllustList(IllustRankingData data)
+        protected override IEnumerable<IllustItem> DoGetIllustList(IllustRankingData data, out int tag)
         {
+            tag = currentPage;
             if (lastQueryKey != null && lastQueryKey.StartsWith(segmentDates[3]))
             {
                 return data.contents.Where(i => i.illust_type == "0").Select(i => i.ConvertToItem());
diff --git a/Pixiview/Illust/RecommendsPage.xaml.cs b/Pixiview/Illust/RecommendsPage.xaml.cs
index 5ce3f1c..5b0aeee 100644
--- a/Pixiview/Illust/RecommendsPage.xaml.cs
+++ b/Pixiview/Illust/RecommendsPage.xaml.cs
@@ -198,8 +198,9 @@ namespace Pixiview.Illust
             }
         }
 
-        protected override IEnumerable<IllustItem> DoGetIllustList(IllustData data)
+        protected override IEnumerable<IllustItem> DoGetIllustList(IllustData data, out int tag)
         {
+            tag = 0;
             if (data.body == null)
             {
                 return null;
diff --git a/Pixiview/Illust/RelatedIllustsPage.xaml.cs b/Pixiview/Illust/RelatedIllustsPage.xaml.cs
index 91c2b8f..5324422 100644
--- a/Pixiview/Illust/RelatedIllustsPage.xaml.cs
+++ b/Pixiview/Illust/RelatedIllustsPage.xaml.cs
@@ -39,8 +39,9 @@ namespace Pixiview.Illust
         protected override bool IsAutoReload => false;
         protected override ActivityIndicator LoadingIndicator => activityLoading;
 
-        protected override IEnumerable<IllustItem> DoGetIllustList(IllustRecommendsData data)
+        protected override IEnumerable<IllustItem> DoGetIllustList(IllustRecommendsData data, out int tag)
         {
+            tag = startIndex;
             if (data.body == null)
             {
                 return null;
diff --git a/Pixiview/Illust/UserIllustPage.xaml.cs b/Pixiview/Illust/UserIllustPage.xaml.cs
index 4a08915..b1a0fb5 100644
--- a/Pixiview/Illust/UserIllustPage.xaml.cs
+++ b/Pixiview/Illust/UserIllustPage.xaml.cs
@@ -51,8 +51,9 @@ namespace Pixiview.Illust
         protected override bool IsAutoReload => false;
         protected override ActivityIndicator LoadingIndicator => activityLoading;
 
-        protected override IEnumerable<IllustItem> DoGetIllustList(IllustUserData data)
+        protected override IEnumerable<IllustItem> DoGetIllustList(IllustUserData data, out int tag)
         {
+            tag = startIndex;
             if (data.body == null)
             {
                 return null;
diff --git a/Pixiview/Utils/Extensions.cs b/Pixiview/Utils/Extensions.cs
index b81ced3..c5184cf 100644
--- a/Pixiview/Utils/Extensions.cs
+++ b/Pixiview/Utils/Extensions.cs
@@ -96,7 +96,7 @@ namespace Pixiview.Utils
 
     public class ParallelTask : IDisposable
     {
-        public static ParallelTask Start(string tag, int from, int toExclusive, int maxCount, Predicate<int> action, Action complete = null)
+        public static ParallelTask Start(string tag, int from, int toExclusive, int maxCount, Predicate<int> action, int tagIndex = -1, Action complete = null)
         {
             if (toExclusive <= from)
             {
@@ -106,7 +106,7 @@ namespace Pixiview.Utils
                 }
                 return null;
             }
-            var task = new ParallelTask(tag, from, toExclusive, maxCount, action, complete);
+            var task = new ParallelTask(tag, from, toExclusive, maxCount, action, tagIndex, complete);
             return task.Start();
         }
 
@@ -114,6 +114,7 @@ namespace Pixiview.Utils
         private int count;
         private bool disposed;
 
+        public int TagIndex { get; private set; }
         private readonly string tag;
         private readonly int max;
         private readonly int from;
@@ -121,7 +122,7 @@ namespace Pixiview.Utils
         private readonly Predicate<int> action;
         private readonly Action complete;
 
-        private ParallelTask(string tag, int from, int to, int maxCount, Predicate<int> action, Action complete)
+        private ParallelTask(string tag, int from, int to, int maxCount, Predicate<int> action, int tagIndex, Action complete)
         {
             if (maxCount <= 0)
             {
@@ -132,6 +133,7 @@ namespace Pixiview.Utils
             {
                 throw new ArgumentOutOfRangeException(nameof(from));
             }
+            TagIndex = tagIndex;
             this.tag = tag;
             this.from = from;
             this.to = to;
diff --git a/Pixiview/Utils/Stores.cs b/Pixiview/Utils/Stores.cs
index 426c2a7..289d0e9 100644
--- a/Pixiview/Utils/Stores.cs
+++ b/Pixiview/Utils/Stores.cs
@@ -721,7 +721,7 @@ namespace Pixiview.Utils
         public const string FavoriteTypeKey = "favorite_type";
 
         public const int MaxPageThreads = 3;
-        public const int MaxThreads = 4;
+        public const int MaxThreads = 8;
         public const string Referer = "https://www.pixiv.net/";
         public const string RefererIllust = "https://www.pixiv.net/artworks/{0}";
         public const string RefererIllustRanking = "https://www.pixiv.net/ranking.php?{0}";
diff --git a/Pixiview/Utils/Ugoira.cs b/Pixiview/Utils/Ugoira.cs
index b793ba6..5ab814b 100644
--- a/Pixiview/Utils/Ugoira.cs
+++ b/Pixiview/Utils/Ugoira.cs
@@ -294,7 +294,7 @@ namespace Pixiview.Utils
                     downloadTask.Dispose();
                     downloadTask = null;
                 }
-                downloadTask = ParallelTask.Start("ugoira.download", 0, inSegs.Count, 2, i =>
+                downloadTask = ParallelTask.Start("ugoira.download", 0, inSegs.Count, 3, i =>
                 {
                     var seg = inSegs[i];
 #if DEBUG