diff --git a/td/generate/scheme/td_api.tl b/td/generate/scheme/td_api.tl
index 1ec06d876..4f178b33b 100644
--- a/td/generate/scheme/td_api.tl
+++ b/td/generate/scheme/td_api.tl
@@ -422,8 +422,9 @@ sticker id:int64 set_id:int64 width:int32 height:int32 emoji:string format:Stick
 //@supports_streaming True, if the video is supposed to be streamed
 //@minithumbnail Video minithumbnail; may be null
 //@thumbnail Video thumbnail in JPEG or MPEG4 format; as defined by the sender; may be null
+//@preload_prefix_size Number of bytes from the video file beginning, which is enough to load to play the video for one second; 0 if unknown. Currently, it is expected to be known only for video stories
 //@video File containing the video
-video duration:int32 width:int32 height:int32 file_name:string mime_type:string has_stickers:Bool supports_streaming:Bool minithumbnail:minithumbnail thumbnail:thumbnail video:file = Video;
+video duration:int32 width:int32 height:int32 file_name:string mime_type:string has_stickers:Bool supports_streaming:Bool minithumbnail:minithumbnail thumbnail:thumbnail preload_prefix_size:int32 video:file = Video;
 
 //@description Describes a video note. The video must be equal in width and height, cropped to a circle, and stored in MPEG4 format
 //@duration Duration of the video, in seconds; as defined by the sender
diff --git a/td/telegram/DocumentsManager.cpp b/td/telegram/DocumentsManager.cpp
index 756355da6..acb52fbec 100644
--- a/td/telegram/DocumentsManager.cpp
+++ b/td/telegram/DocumentsManager.cpp
@@ -122,9 +122,11 @@ Document DocumentsManager::on_get_document(RemoteDocument remote_document, Dialo
     }
   }
   int32 video_duration = 0;
+  int32 video_preload_prefix_size = 0;
   string video_waveform;
   if (video != nullptr) {
     video_duration = static_cast<int32>(std::ceil(video->duration_));
+    video_preload_prefix_size = video->preload_prefix_size_;
     auto video_dimensions = get_dimensions(video->w_, video->h_, "documentAttributeVideo");
     if (dimensions.width == 0 || (video_dimensions.width != 0 && video_dimensions != dimensions)) {
       if (dimensions.width != 0) {
@@ -527,7 +529,7 @@ Document DocumentsManager::on_get_document(RemoteDocument remote_document, Dialo
       td_->videos_manager_->create_video(file_id, std::move(minithumbnail), std::move(thumbnail),
                                          std::move(animated_thumbnail), has_stickers, vector<FileId>(),
                                          std::move(file_name), std::move(mime_type), video_duration, dimensions,
-                                         supports_streaming, !is_web);
+                                         supports_streaming, video_preload_prefix_size, !is_web);
       break;
     case Document::Type::VideoNote:
       td_->video_notes_manager_->create_video_note(file_id, std::move(minithumbnail), std::move(thumbnail),
diff --git a/td/telegram/InlineQueriesManager.cpp b/td/telegram/InlineQueriesManager.cpp
index 8caba2e15..c9281d84d 100644
--- a/td/telegram/InlineQueriesManager.cpp
+++ b/td/telegram/InlineQueriesManager.cpp
@@ -1322,7 +1322,7 @@ template <>
 tl_object_ptr<td_api::video> copy(const td_api::video &obj) {
   return td_api::make_object<td_api::video>(obj.duration_, obj.width_, obj.height_, obj.file_name_, obj.mime_type_,
                                             obj.has_stickers_, obj.supports_streaming_, copy(obj.minithumbnail_),
-                                            copy(obj.thumbnail_), copy(obj.video_));
+                                            copy(obj.thumbnail_), obj.preload_prefix_size_, copy(obj.video_));
 }
 
 template <>
diff --git a/td/telegram/MessageContent.cpp b/td/telegram/MessageContent.cpp
index 965aab284..86a73d5cd 100644
--- a/td/telegram/MessageContent.cpp
+++ b/td/telegram/MessageContent.cpp
@@ -2101,10 +2101,11 @@ static Result<InputMessageContent> create_input_message_content(
       ttl = input_video->self_destruct_time_;
 
       bool has_stickers = !sticker_file_ids.empty();
-      td->videos_manager_->create_video(
-          file_id, string(), thumbnail, AnimationSize(), has_stickers, std::move(sticker_file_ids),
-          std::move(file_name), std::move(mime_type), input_video->duration_,
-          get_dimensions(input_video->width_, input_video->height_, nullptr), input_video->supports_streaming_, false);
+      td->videos_manager_->create_video(file_id, string(), thumbnail, AnimationSize(), has_stickers,
+                                        std::move(sticker_file_ids), std::move(file_name), std::move(mime_type),
+                                        input_video->duration_,
+                                        get_dimensions(input_video->width_, input_video->height_, nullptr),
+                                        input_video->supports_streaming_, 0, false);
 
       content = make_unique<MessageVideo>(file_id, std::move(caption), input_video->has_spoiler_ && !is_secret);
       break;
diff --git a/td/telegram/VideosManager.cpp b/td/telegram/VideosManager.cpp
index b4705be55..7bbc70eef 100644
--- a/td/telegram/VideosManager.cpp
+++ b/td/telegram/VideosManager.cpp
@@ -46,10 +46,10 @@ tl_object_ptr<td_api::video> VideosManager::get_video_object(FileId file_id) con
   auto thumbnail = video->animated_thumbnail.file_id.is_valid()
                        ? get_thumbnail_object(td_->file_manager_.get(), video->animated_thumbnail, PhotoFormat::Mpeg4)
                        : get_thumbnail_object(td_->file_manager_.get(), video->thumbnail, PhotoFormat::Jpeg);
-  return make_tl_object<td_api::video>(video->duration, video->dimensions.width, video->dimensions.height,
-                                       video->file_name, video->mime_type, video->has_stickers,
-                                       video->supports_streaming, get_minithumbnail_object(video->minithumbnail),
-                                       std::move(thumbnail), td_->file_manager_->get_file_object(file_id));
+  return make_tl_object<td_api::video>(
+      video->duration, video->dimensions.width, video->dimensions.height, video->file_name, video->mime_type,
+      video->has_stickers, video->supports_streaming, get_minithumbnail_object(video->minithumbnail),
+      std::move(thumbnail), video->preload_prefix_size, td_->file_manager_->get_file_object(file_id));
 }
 
 FileId VideosManager::on_get_video(unique_ptr<Video> new_video, bool replace) {
@@ -66,11 +66,13 @@ FileId VideosManager::on_get_video(unique_ptr<Video> new_video, bool replace) {
       v->mime_type = std::move(new_video->mime_type);
     }
     if (v->duration != new_video->duration || v->dimensions != new_video->dimensions ||
-        v->supports_streaming != new_video->supports_streaming) {
+        v->supports_streaming != new_video->supports_streaming ||
+        v->preload_prefix_size != new_video->preload_prefix_size) {
       LOG(DEBUG) << "Video " << file_id << " info has changed";
       v->duration = new_video->duration;
       v->dimensions = new_video->dimensions;
       v->supports_streaming = new_video->supports_streaming;
+      v->preload_prefix_size = new_video->preload_prefix_size;
     }
     if (v->file_name != new_video->file_name) {
       LOG(DEBUG) << "Video " << file_id << " file name has changed";
@@ -169,7 +171,7 @@ void VideosManager::merge_videos(FileId new_id, FileId old_id) {
 void VideosManager::create_video(FileId file_id, string minithumbnail, PhotoSize thumbnail,
                                  AnimationSize animated_thumbnail, bool has_stickers, vector<FileId> &&sticker_file_ids,
                                  string file_name, string mime_type, int32 duration, Dimensions dimensions,
-                                 bool supports_streaming, bool replace) {
+                                 bool supports_streaming, int32 preload_prefix_size, bool replace) {
   auto v = make_unique<Video>();
   v->file_id = file_id;
   v->file_name = std::move(file_name);
@@ -182,6 +184,7 @@ void VideosManager::create_video(FileId file_id, string minithumbnail, PhotoSize
   v->thumbnail = std::move(thumbnail);
   v->animated_thumbnail = std::move(animated_thumbnail);
   v->supports_streaming = supports_streaming;
+  v->preload_prefix_size = preload_prefix_size;
   v->has_stickers = has_stickers;
   v->sticker_file_ids = std::move(sticker_file_ids);
   on_get_video(std::move(v), replace);
diff --git a/td/telegram/VideosManager.h b/td/telegram/VideosManager.h
index 200b46ac9..d8572a776 100644
--- a/td/telegram/VideosManager.h
+++ b/td/telegram/VideosManager.h
@@ -36,7 +36,8 @@ class VideosManager {
 
   void create_video(FileId file_id, string minithumbnail, PhotoSize thumbnail, AnimationSize animated_thumbnail,
                     bool has_stickers, vector<FileId> &&sticker_file_ids, string file_name, string mime_type,
-                    int32 duration, Dimensions dimensions, bool supports_streaming, bool replace);
+                    int32 duration, Dimensions dimensions, bool supports_streaming, int32 preload_prefix_size,
+                    bool replace);
 
   tl_object_ptr<telegram_api::InputMedia> get_input_media(FileId file_id,
                                                           tl_object_ptr<telegram_api::InputFile> input_file,
@@ -75,6 +76,7 @@ class VideosManager {
     string minithumbnail;
     PhotoSize thumbnail;
     AnimationSize animated_thumbnail;
+    int32 preload_prefix_size = 0;
 
     bool supports_streaming = false;
 
diff --git a/td/telegram/VideosManager.hpp b/td/telegram/VideosManager.hpp
index a41e62b2d..42ec0d10b 100644
--- a/td/telegram/VideosManager.hpp
+++ b/td/telegram/VideosManager.hpp
@@ -22,10 +22,12 @@ void VideosManager::store_video(FileId file_id, StorerT &storer) const {
   const Video *video = get_video(file_id);
   CHECK(video != nullptr);
   bool has_animated_thumbnail = video->animated_thumbnail.file_id.is_valid();
+  bool has_preload_prefix_size = video->preload_prefix_size != 0;
   BEGIN_STORE_FLAGS();
   STORE_FLAG(video->has_stickers);
   STORE_FLAG(video->supports_streaming);
   STORE_FLAG(has_animated_thumbnail);
+  STORE_FLAG(has_preload_prefix_size);
   END_STORE_FLAGS();
   store(video->file_name, storer);
   store(video->mime_type, storer);
@@ -40,16 +42,21 @@ void VideosManager::store_video(FileId file_id, StorerT &storer) const {
   if (has_animated_thumbnail) {
     store(video->animated_thumbnail, storer);
   }
+  if (has_preload_prefix_size) {
+    store(video->preload_prefix_size, storer);
+  }
 }
 
 template <class ParserT>
 FileId VideosManager::parse_video(ParserT &parser) {
   auto video = make_unique<Video>();
   bool has_animated_thumbnail;
+  bool has_preload_prefix_size;
   BEGIN_PARSE_FLAGS();
   PARSE_FLAG(video->has_stickers);
   PARSE_FLAG(video->supports_streaming);
   PARSE_FLAG(has_animated_thumbnail);
+  PARSE_FLAG(has_preload_prefix_size);
   END_PARSE_FLAGS();
   parse(video->file_name, parser);
   parse(video->mime_type, parser);
@@ -66,6 +73,9 @@ FileId VideosManager::parse_video(ParserT &parser) {
   if (has_animated_thumbnail) {
     parse(video->animated_thumbnail, parser);
   }
+  if (has_preload_prefix_size) {
+    parse(video->preload_prefix_size, parser);
+  }
   if (parser.get_error() != nullptr || !video->file_id.is_valid()) {
     return FileId();
   }